153
Contents

1.5.1 Introduction 155

1.5.2 Organization 156

1.5.3 Personnel and Supervision 157

1.5.3.1 Attributes of container nursery managers 157

1.5.3.2 Professional attitudes 157

Technical competence 157

Clear managerial goals 157

Relating to the crop 157

Commitment to the nursery 158

Cleanliness 158

1.5.3.3 Supervision 159

1.5.3.4 Safety programs 159

1.5.3.5 Operational planning 160

1.5.4 Data Collection and Analysis 161

1:5.4.1 Financial and production records 161

1.5.4.2 Cultural records 161 

Growing schedules 162

 Environmental conditions 163 

Crop development 164

1.5.5 Nursery Problem Solving 169

1.5.5.1 Principles of crisis management 170

Be prepared 170

Use all of your senses all of the time 170

Be alert to problem development 171

1.5.5.2 Temperature crises 172

Unusual cold 172

Excessive heat 174

1.5.5.3 Fire 175

1.5.5.4 Water crises 175

Flooding 175

Lack of water 176

1.5.5.5 Cultural problems 176

Delayed or erratic germination 176

Growth rate behind schedule 177

Premature dormancy 177

Foliar symptoms 179

Abnormal growth patterns 180

Pest problems 183

154

1.5.6 Customer Relations 186

1.5.7 Summary 187

1.5.8 References 188

1.5.8.1 General nursery management 188

1.5.8.2 Literature cited 188
1.5.1 Introduction

The final phase of nursery development begins when the 

construction is complete and it's time to plan for that first 

crop! The challenge of managing a container nursery 

can be intimidating to a new manager, and so the 

purpose of this chapter is to outline the various aspects 

of nursery management. Although individual management styles differ with personality types and specific 

objectives, there are several key aspects of every successful nursery: solid organization, professional personnel, a system of data collection and analysis, and an 

established system for solving problems. None of these 

are unique to container tree nurseries, and good general 

information on nursery management can be found in the 

general horticulture references listed in section 1.5.8.1.

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1.5.2 Organization

If it is to succeed, the management of a nursery must 

have a structured organization that ensures that responsibilities are assigned and jobs get done. The responsibilities for a container tree nursery can be divided into four 

general categories (Nelson 1991):

1. Production—performing the day-to-day cultural 

operations of growing the crop. 

2. Engineering—maintaining the physical plant and 

custom-building any special equipment. 

3. Marketing—soliciting orders, delivering the crop, 

and providing whatever other customer services are 

needed. 

4. Business affairs—keeping business records and 

accounting costs, bills, purchases, and payrolls.

In small nurseries, the manager may also be the owner 

and may also perform all, or nearly all, of these functions. 

As the nursery grows in size, the manager must delegate 

responsibilities for various parts of the job to assistants, 

which is the beginning of a hierarchical organization. 

Often, the first professional employee that a new nursery 

manager hires is a grower. This person acts as 

production manager, leaving the other general business 

duties to the nursery manager. Growers usually supervise 

the general laborers, but supervision is delegated to crew 

leaders in larger nurseries.

Regardless of the organizational structure, any successful 

nursery must have one characteristic: unity of command. Nursery managers must establish a clear assignment of responsibilities, together with the authority to 

carry them out. Raising a crop of container seedlings is 

not a simple procedure. Consequently, because nursery 

managers are most knowledgeable about day-to-day 

operations and will ultimately be held responsible, only 

they should direct nursery activities, make changes in 

growing schedules, and regulate the setting of environmental control equipment. In nurseries where there has 

not been a clear assignment of responsibility, trouble 

eventually develops.

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1.5.3 Personnel and Supervision

1.5.3.1 Attributes of container nursery managers

One of the most difficult decisions that a nursery developer must make is hiring the nursery manager. The 

purpose of this section is to provide a brief glimpse of 

what to look for in nursery managers, and what makes 

them unique. Managers can be described as organizers, 

planners, people capable of great capacity for work, 

decision-makers, diplomats, problem solvers, firm 

believers that all activities must be for the betterment of 

the business, people of good judgment, and who are 

knowledgeable, honest, and forthright, and challenged 

by the accomplishment of the job (Nelson 1991).

It is rare to find all of these sterling qualities in one 

person, but the definition illustrates the multifaceted 

nature of the manager's job. Managers must be honest 

and be able to think and reason quickly and clearly. 

Problems will arise that will require solutions that can only 

be arrived at by careful analysis and deduction. Container 

nursery managers must know about propagation 

structures, seedling morphology and physiology, and the 

economics and management of a private business or 

government organization. They must have sufficient 

intellect and self-assurance to handle business management procedures, personnel management, physical 

facility management, crop rotations and scheduling, 

seedling culture, marketing, and delivery. If the nursery is 

part of a larger organization, staff and other managers 

may share these loads and help with these jobs. However, the nursery manager must see that overall management is coordinated.

1.5.3.2 Professional 

attitudes

Managing a container nursery facility is more than just 

growing a crop. Successful nursery managers must 

possess certain key professional attitudes that guide 

their daily work and provide an example for their 

employees.

Technical competence. Traditionally, forest nursery 

managers have come from the ranks of the forestry 

profession. There are good reasons for this, not the least 

of which is that foresters with field experience know how 

difficult tree planting is and how important it is that each 

seedling be a good one. However, foresters must learn 

to grow container tree seedlings by observation, trial and 

error, and studying technical publications. While this 

process for developing nursery managers has

some drawbacks, the process has developed a 

stable core of nursery professionals. In recent years, 

more container nursery manager and grower 

positions are being filled by horticulturists.

Good nursery managers do not have to be foresters, 

horticulturists, or botanists. Regardless of their background or training, the key factor is that managers 

understand the daily operations of a container nursery 

and are able to grow tree seedlings. Managers and 

growers must have the knowledge-either from formal 

training or from experience-to understand how seedlings react to cultural treatments.

Clear managerial goals. Nursery managers must be 

allowed to grow the seedlings. Too often, especially at 

large government nurseries, they are buried by administrative details because they are the senior manager at the 

site. This is a waste of resources and poor management. 

Adequate support staff must be provided to allow nursery 

managers to do the real job they were hired to do.

The mission of the nursery must be kept foremost in the 

minds of managers and their staffs, and it is helpful to state 

that mission in terms of a concrete goal. For example, a 

goal might be "to grow high-quality seedlings at a 

reasonable cost." Often, the details of nursery 

development, personnel problems, maintenance work, or 

preoccupations with other related activities can unwittingly 

override the prime reason for the nursery. This is often 

directly attributable to the demands and priorities of higher 

management or owners, who often do not provide 

adequate technical and financial support to avoid 

compromising the primary goal of the nursery.

Relating to the crop. Nursery managers and their staffs 

must learn to "think like a seedling" (fig. 1.5.1). They 

should view nursery activity priorities from the standpoint 

of the biological requirements of the crop. The goal at the 

nursery usually is to grow good seedlings on an 

economical basis. Every member of the crew should have 

at least a rudimentary knowledge of the effects that their 

activities will have on the biological well-being of the 

seedlings. In recent years, the American Association of 

Nurserymen has been emphasizing basic horticultural 

training for nursery workers. This training not only gives 

more meaning to the work they do, but an appreciation of 

the effect of their activities on the plants being grown.

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Commitment to the nursery. A container nursery cannot 

be run "by committee." Instead, one person always has to 

accept primary responsibility for the crop at any particular 

time. For example, if the photoperiod light system fails 

even for one night, the seedlings may lapse into bud 

dormancy and not begin shoot growth again until the 

following year. Even if seedlings can be forced to grow 

again, this one oversight means the crop will be seriously 

delayed and a growing contract may be lost. Problems 

always develop when there is no one person who 

conscientiously looks after the crop and the functioning of 

the nursery all the time.

Growing container seedlings involves precise control of 

the propagation environment, so that it is optimal for 

seedling growth. This is a great advantage, but at the 

same time, managers have more responsibilities for the 

well-being of the crop than do managers of bareroot 

nurseries. Nature provides buffers against plant damage 

in the bareroot nursery environment, including a large 

volume of soil to supply water and nutrients, and natural 

late summer conditioning of plants so that they are 

prepared for winter. A fully controlled greenhouse has 

few of these natural buffers and so there is little room for 

error. The price of rapid seedling growth in container 

nurseries is knowledge and constant vigilance.

Cleanliness. The cheapest insurance against disease, 

insect, mechanical, or seedling physiological problems in 

a container nursery is to keep everything clean and in 

good working order. Not only is cleanliness advised for 

sanitation, but it is also good business management. It is 

much easier to sell seedlings to visiting potential tree 

buyers or potential supporters within the organization if 

the nursery is clean, orderly, and well manicured. Visitors 

equate a clean, neat nursery with efficiency and good 

management; indeed, this usually proves to be correct.

The emphasis on cleanliness, neatness, and 

maintenance also affects the nursery workers. By 

emphasizing these things and providing a good example, 

nursery managers are saying "we care about this place; it 

reflects on you as well as us; it is going to be something 

we can all be proud of." Under these conditions, workers, 

especially long-time employees, will respond with added 

pride in their work and feel they belong and have a stake 

in the nursery.

Such education will often prevent disastrous errors on 

the part of container nursery workers who, for instance, 

might not understand the implications for the crop of 

turning down the heat in the propagation structure 

because "it is too hot to work comfortably." In the final 

analysis, managers are the prime trainers of the crew. 

Their knowledge and attitude toward the crop will 

largely determine how well their crew learns to "think 

like a seedling."

158
1.5.3.3 Supervision

Both Nelson (1991) and Hanan and others (1978) provide 

excellent sections in their texts on supervision, and there 

is a wealth of other literature on the subject. However, a 

few particular comments for nursery managers are 

appropriate here. First, the characteristics of a successful 

container nursery proceed directly from the nursery 

manager's example or, as Nelson (1991) puts it: "labor 

management begins with the management of oneself." 

Also, the wise supervisor makes sure that workers 

understand several things:

1. What the management structure of the organization 

is and who their immediate boss is. 

2. What the goals of the nursery and/or parent 

organization are. 

3. What their direct responsibilities are and how their 

authority relates to the remainder of the work force. 

4. How their performance will be evaluated and what 

the monetary and professional rewards will be.

Successful supervision is also connected to the work 

environment, expectations, and opportunities for 

employee betterment. As mentioned earlier, a clean, 

orderly work environment combined with high productquality standards not only provide employees with a 

better place to work but also generate pride in their work. 

High expectations for employees, in terms of work quality 

or quantity, generally will lead to a rise in personal 

expectations on the part of each worker and more 

self-esteem. Opportunities for advancement and

education (on or off the job) have often proven just as 

important, or more so, than pay in motivating employees.

1.5.3.4 Safety programs

Greenhouses and other propagation structures have a 

number of inherent safety hazards that can be minimized 

by proper design and construction and by safe work habits 

(Goldsberry 1979). Probably the greatest hazard created 

by wetness is the danger of electrical shock. All wiring 

should be in waterproof conduit. All outlets should be 

grounded and equipped with ground fault interrupters. 

Ungrounded tools or appliances of any kind should never 

be used in a container growing structure, unless they are 

double insulated. Power must be shut off first when 

electrical equipment is being repaired or adjusted.

Propagation structures contain many other hazards. 

Equipment, such as ventilation fans and conveyors, may 

start automatically without warning. For this reason, 

blades and other moving parts should be shielded so that 

no one can put fingers in them. Some structures have 

floor-mounted heaters, which should have their flues 

shielded so that they cannot be touched inadvertently. 

Pesticide storage areas must be properly designed, and 

all employees (not just applicators) must be given regular 

training on pesticide use in enclosed areas. (Pesticide 

storage and safety are discussed in detail in section 

5.1.8 in volume five of this series.)

Many potential safety problems can be averted by 

maintaining a neat, clean work area. Tools and other 

equipment should never be left lying around, and hoses 

or cords should be coiled and placed out of traffic areas. 

Propagation areas are often humid, which makes floors 

slippery, especially if algae has been allowed to grow. 

Floors should be built to drain properly and should be 

cleaned as needed to prevent slippery conditions from 

developing.

Safety meetings should be held at the start of each major 

work period, such as sowing or grading and packing. 

These meetings are an excellent opportunity to inform 

new employees and remind returning workers of possible 

hazards and to show them the best ways to do tasks 

safely. Some tasks have proven to be particularly 

dangerous, such as pulling seedlings from their 

containers during packing, which often causes tendonitis 

and carpal tunnel syndrome (Wallersteiner 1988). Like 

most work-related injuries, however, they can be reduced 

by proper training and worker awareness (fig. 1.5.2).

159
1.5.3.5 Operational planning

Operational planning is the advance work that brings all 

the non-structural requirements of nursery production 

(labor, supplies, equipment, etc.) together at key times of 

the production process. Operational planning is what 

allows seedling production to proceed smoothly and 

efficiently and is an important, but often neglected, part of 

container tree nursery management. Nursery managers 

often tend to concentrate on the daily details of growing 

seedlings while neglecting to plan for future needs. 

Operational planning is especially important in nurseries 

because of the seasonal nature of the work and 

requirements for labor and resources at specific, limited 

time periods, such as during the sowing and packing 

seasons.

For planning purposes, a container tree nursery can be 

visualized as a system that consists of a series of sequential processes (filling and sowing the containers), operations (placing a specified number of seeds per container), 

and the requirements (propagation structure, seeder 

equipment, labor, and supplies) to complete each process. 

Good managers assure that all processes are scheduled 

in the proper sequence and that all the requirements for a 

specific operation come together at the right time and 

place. (The requirements of a container nursery system 

are discussed in more detail in section 1.1.4.1, and the 

organizational framework is diagrammed in table 1.1.5.)

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1.5.4 Data Collection and Analysis

The third important aspect of nursery management is the 

collection and analysis of information. The types of 

records and the methods of information collection and 

storage will vary considerably with the type, size, and 

complexity of the nursery. The purpose of this section is 

not to specify any particular record keeping method but 

rather to introduce the terms and concepts necessary to 

start managing a nursery and to impress on new nursery 

managers the importance of keeping good records right 

from the start. The types of records kept at a container 

nursery fall into two general categories: financial and 

production records, and cultural records.

1.5.4.1 Financial and production records

Financial records are kept to account for expenditures, to 

control the budget, and to provide the records necessary 

for improving procedures for conducting business in the 

future. Financial records also are kept to meet 

governmental requirements (including tax purposes) and 

as aids in obtaining credit.

A financial record keeping system should be designed 

to document three general classes of information: (1) 

expense data, (2) production data, and (3) unit-cost 

data. The data can be recorded by individual nursery 

operation (such as "sowing") but can also be used to 

analyze other production variables such as species, 

container size, and even customer. Information on 

seedling production costs should be organized to reflect 

different cost centers including supplies, utilities, 

services, and labor. Analysis of this information may 

show nursery managers where costs are excessive and 

help make management decisions, such as whether a 

winter crop can be financially justified (table 1.5.1). 

Because labor is such a large component of production 

costs, nursery managers should collect the number of 

hours spent on each task along with the number of 

seedlings processed. This information can then be 

analyzed and formatted to produce tables (table 1.5.2) 

that can be invaluable in making sound business 

decisions such as whether to invest in new labor-saving 

equipment.

Financial records should also include detailed production 

data regarding operational information such as "hours of 

labor spent filling containers" or "bags of fertilizer 

purchased" or "numbers of a certain species of tree 

seedlings shipped." Such production information, 

blended with the cost portions of financial records, is the

basis for making many management decisions, 

especially regarding materials purchasing, next year's 

budget, or other operational, cultural, or maintenance 

activities. Ultimately such financial data are used to 

calculate unit output costs (dollars per thousand 

seedlings). This latter information is essential for setting 

accurate prices and estima ting future production costs 

when bidding on seedling growing contracts.

The sophistication of financial record keeping will vary 

with the size and complexity of the facility. A small 

nursery may find it completely adequate to maintain 

written records in a log book, whereas this would be 

difficult for a larger facility. Modern computer-based 

record systems make record keeping much easier, 

especially the sorting of the data into different categories 

and displays for analysis. Many business and computer 

consultants and software packages are available to help 

the inexperienced manager. For example, a computer 

program called "Greenhouse Cost Accounting" enables 

the nursery manager to perform detailed cost accounting 

and calculate the profitability of container crops 

(Brumfield 1992). This software is particularly useful 

because it allows the user to allocate variable costs to 

any number of individual crops on an area basis, a task 

that would be extremely tedious without the benefit of a 

computer.

Needs change with size and sophistication of the nursery 

and so, at various points during the development of a 

nursery facility, the manager should check to see if the 

financial record system is still adequate to meet the 

needs of the nursery.

1.5.4.2 Cultural records

Cultural records are maintained to provide a plan for 

duplicating successful crops and give an accounting that 

can be used in (a) determining the cause of errors in the 

culture of the crop, (b) deciding on action taken on the 

current crop, and (c) making plans to avoid problems with 

future crops (Nelson 1991). The following is a general 

outline of the types of cultural records that should be 

made (a more detailed discussion will be given in volume 

six of this series).

Cultural records fall into three categories: growing 

schedules, environmental conditions in the propagation 

area, and crop development records.

161
Growing schedules. These written plans of crop timing 

are essential to successful nursery management and are 

developed prior to sowing based on the best information 

and experience available. Growing schedules come in 

various degrees of sophistication and refinement. They 

may be only rough outlines of dates for key cultural 

processes, such as sowing, thinning, and harvesting, or 

they can provide considerable detail on each step of the 

process together with a record of actual accomplishment 

(Tinus and McDonald 1979). The best growing 

schedules include a variety of operational 

considerations.

162

related to crop timing, culture, and growing space

utilization. They should include

1. Target specifications for the crop and the time of 

delivery.

2. Adequate allowance of time for seed stratification, if 

needed, prior to sowing and for a proper hardening period 

prior to shipment.

3. Placing species or container types with similar growth 

regimes in the same propagation environment.
4. Planning efficient use of space in the propagation 

environment to allow large blocks of similar trees to 

be sown at the same time and, if possible, placing 

seedlings to be removed first near the perimeter or 

doors for ease of handling.

Growing schedules should serve as a daily reminder to 

the nursery manager about the operations to be done and 

should, in aggregate for the various crops being grown, 

serve as the basis for work force and materials planning 

on a week-to-week basis. (Procedures on how to develop 

growing schedules and several examples will be provided 

in volume six, chapter 1, of this series.)

Environmental conditions. This set of culture-related 

records contains such things as temperatures inside and 

outside the propagation structure, solar radiation intensity, 

growing medium nutrient analysis, foliar nutrient analysis, 

occurrence of insect pests and disease, and other general 

observations (Nelson 1991). These records not only show 

the crop environment maintained but also will indicate 

various equipment failures and any involuntary deviations 

from the growing schedule. Abnormal crop conditions 

discovered later can often be related back to mechanical 

failures as indicated in the environmental records.

Daily or weekly records of environmental conditions and 

seedling growth can be charted by hand on clipboards 

mounted near the work area. This system has the 

advantage of being readily accessible and simple (fig. 

1.5.3A). Record sheets can be 3-hole punched and 

assembled in a ring binder for late review and then filed. 

Hygrothermographs are handy ways to permanently 

record temperature and humidity. In recent years, 

environmental control computers are commonly used not 

only to control conditions in the propagation environment 

but also to provide a handy way to spot-check conditions 

throughout the growing area (fig. 1.5.3B). This weather 

information is constantly stored on disk and can be used 

to plot and analyze trends, which can help nursery 

managers spot problems quickly and take corrective 

action before serious growth loss occurs.

163
Crop development. All nurseries should keep some form 

of permanent records that monitor the growth and

development of their crops over the growing season. 

Nursery managers should monitor significant events such 

as speed of germination and development of dormant 

buds, and also take periodic measurements of growth 

parameters including shoot height and stem diameter 

(caliper). Root growth is more difficult to monitor because 

small seedlings are damaged when removed from the 

container unless book containers (which are specifically 

designed to facilitate root monitoring) are used. Although it 

requires destructive sampling, seedling ovendry weight is 

a useful index of crop development and is necessary for 

the calculation of shoot-to-root (S:R) ratios.

It is best to appoint one person—the crop monitor—

responsible for taking all seedling development and 

inventory measurements. This ensures that the 

measurements are taken the same way each time and, 

because they becomes intimately familiar with crop 

development, crop monitors are invaluable as a pest 

detection specialists. Seedling height can easily be taken 

with a ruler and stem diameter with calipers, and the data 

recorded on prepared data forms (fig. 1.5.4A). Digital 

calipers that are easier to read and can be linked to 

portable data recorders are now available (fig. 1.5.4B).

Ambient weather conditions should also be collected in 

a standard weather station, including daily temperature 

highs and lows, humidity, precipitation, and wind 

speed. Weather changes often are directly related to 

environmental conditions inside growing structures, and 

so these records can reveal problems with the 

environmental control system. Computers should be 

linked to outside weather sensors to provide a 

complete picture of the daily weather and seasonal 

climate trends, and the data can be automatically 

transferred directly to computers for permanent 

storage. Weather records are very valuable data that 

can tell the nursery manager how to design and 

operate propagation structures and how to acclimate 

crops, as well as provide a way of evaluating the risk of 

potentially damaging weather occurrences.

164
Manually measured data can be entered into preprogrammed data 

recorders and then electronically downloaded into customized 

computer files. Nurseries with computer systems can merge this 

information with environmental and cultural records to generate 

sophisticated crop models and optimize growing schedules.

The growing media and the seedlings themselves can be 

chemically analyzed to determine the nutrient level of 

each of the mineral nutrients. Most nurseries collect 

representative samples of growing media or seedling 

foliage and send them to commercial testing laboratories. 

This information is valuable in helping nursery managers 

identify and correct nutrition problems, and in testing new 

fertilization regimes. For example, trials with black 

spruce—Picea mariana (Mill.) B.S.P.-showed that 

increasing the fertilizer rate by 50% improved the growth 

rate, but that doubling the rate caused a reduction in 

seedling quality (table 1.5.3). The total dry weight 

decreased and the shoots became too large, as reflected 

by the high shoot-to-root ratio. Foliar nitrogen content was 

too high for good survival and growth, and the high nitrate 

level in the growing medium could lead to undesirable 

agricultural pollution of runoff water. (See section 4.1.9 in 

volume four of this series for nutrient testing procedures 

and standards.)

Monitoring the target seedling. Successful nursery 

managers use the concept of the target seedling to 

describe the ideal morphological and physiological 

characteristics of a seedling that will survive and grow on 

a specific outplanting site (Rose and others 1990). The 

target seedling concept is a useful way for seedling users 

to describe what type of seedling they expect, and for 

nursery managers to describe what they can realistically

produce. Because of differences between species and 

environmental conditions on the outplanting site, the 

target seedling will vary from customer to customer.

Morphological attributes-including shoot height, stem 

caliper, and root volume-are the most common 

measurements, but other physiological attributes help 

define the target seedling as well. Physiological 

attributes are categorized as either performance 

attributes (root growth potential, cold hardiness, and 

stress resistance) or material attributes (bud dormancy, 

water relations, nutrition, and morphology). These 

performance attributes are assessed by placing samples 

of seedlings into specified controlled environments and 

evaluating their responses (Ritchie 1984). (Seedling 

quality monitoring will be discussed in more detail in 

volume six of this series.)

165
During the growing season, seedling growth trends can

easily be visualized by graphing shoot height, caliper, and 

seedling dry weight over time (fig. 1.5.5A&B). Although they can 

be plotted by hand, computers make this process easy and the 

information can be stored for future analysis (fig. 1.5.5C). These 

growth charts are invaluable in monitoring crop development 

and adjusting environmental factors and cultural practices 

during the growing season. For example, if one seed lot shows 

slow growth compared to the target growth curve, the nitrogen 

fertilization rate can be increased to bring it up

to expectations (fig. 1.5.5A). Without these charts, growth 

problems are difficult to identi fy early enough to be able to correct 

them. Accumulating growth records over several crops allows the 

nursery manager to reasonably predict seedling growth. Growth 

curves are the basis for refining growing schedules and predicting 

the time and resources necessary to produce the target seedling. 

The effects of unusual weather or other cultural factors on 

seedling quality or delivery time of a crop can also be projected.

166
Towards the end of the growing season, distribution curves of 

height and caliper can be used to illustrate how well a particular 

crop meets its target specifications. Then, the grading (culling) 

standards can be set based on the target seedling dimensions 

and the ability to the crop to meet these expectations. For shoot 

height, the shippable seedlings are usually clustered in a normal 

distribution around the target specification, with the culls distributed 

in both tails of the curve below the minimum and above the 

maximum height standards (fig. 1.5.6A).

The situation for caliper is different, however. Customers prefer 

seedlings with relatively large stem diameters and so will accept 

larger caliper stock as long as it does not exceed the maximum 

height standards. Therefore, seedlings are only graded to a 

minimum standard, and so for caliper, cull seedlings only occur on 

the small end of the curve (fig. 1.5.6B). Grading specifications will 

vary with species and stock type because larger seedlings are 

possible with larger containers and longer crop cycles (table 1.5.4). 

Because each growing season is a

167
little different, the grading standards often have to be adjusted in 

negotiations between the nursery manager and the seedling 

buyer.

Sample size. The number of seedlings to be measured is usually a 

matter of convenience, although for the data to be statistically valid, 

the sample size should be determined by the following formula 

(Day 1979):

X=S2t

2

/AE2

where X =the required number of seedlings

S =the standard deviation t= 

Student's t-value

AE= the allowable error

168

The required number of samples varies with species, type of 

propagation environment, and measurement parameter (table 

1.5.4). For a crop of white spruce—(Picea glauca (Moench) Voss)—

and black spruce in eastern Canada, a sample size of 15 to 25 

seedlings per seedlot would be sufficient when measuring height 

and caliper, but the number increased dramatically to over 60 to 90 

samples if seedling weight was the parameter (Hallett 1982). 

Obviously, this sample size is too large to be practical, but dry 

weights can be quite accurately predicted from caliper and height 

measurements using regression analysis. Regression equations 

must be determined for each species and nursery but, once 

calculated, give the nursery manager an easy-to-estimate ovendry 

weight without destructive sampling.
1.5.5 Nursery Problem Sowing

One of the most important aspects of nursery management is 

solving the day-to-day problems that come up. Although previous 

experience is the best weapon, even novice nursery managers can 

become proficient problem solvers by being prepared and following 

a set procedure (Landis 1984). Atypical problem solving 

procedures consists of five steps (fig. 1.5.7):

1. Identifying the problem—Problemidentification requires 

knowledge and experience. In the early stages, however, 

many problems go unnoticed until the situation reaches a 

critical level. Nursery managers should make regular 

inspections of the crop and train their staff to be alert to 

possible problems.

2. Analyzing the problem—Efficientproblem analysis begins 

with an accurate description of this situation, both what the 

problem is and what it is not. Try to observe with an open mind 

and to separate perceived problems from real ones.

3. Generating ideas—Even though new managers think that 

their situation is unique, the odds are that some one has faced 

this problem before. Information can be gathered from the 

nursery staff, other nurseries, and the published literature.

4. Developing and testing the hypothesis—Managers

must keep an open mind during the evaluation process and 

consider all aspects of the situation. Nursery problems usually 

require prompt action, and so many decisions will have to be 

made on incomplete evidence.

5. Implementing a solution—All nurseries have constraints 

in funding, time, and personnel, and so managers must 

decide what solutions are practical under their own unique 

situation. A follow-up is required to make sure that the 

problem is really solved and so, whenever a corrective 

treatment is applied, control plots should always be left for 

comparison.

Nursery managers can become better problem solvers by

visiting other nurseries, attending workshops and training

sessions, and keeping up with the latest published

literature (fig. 1.5.8).

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1.5.5.1 Principles of crisis management

A crisis is a particularly severe problem that demands immediate 

attention. Some crises require corrective action within minutes; 

others may require a response on a time scale of hours to several 

days. The nursery manager must size up each situation and react 

accordingly. Overreacting can be just as harmful as not acting 

quickly enough, not only for the welfare of the crop, but also for the 

smooth running of the whole nursery. The timing of a crisis can 

never be predicted but, with proper management, the frequency of 

occurrence and the damage done can be minimized.

Be prepared. Although no one can prepare for all possible 

contingencies, there are certain things that can be done ahead of 

time to prevent most emergencies from becoming disasters. Any 

nursery facility has certain standard operating procedures that 

represent the best information available. Therefore, changes in 

cultural procedures, equipment settings, or timing should be made 

with caution. A record of the change should be noted in the 

nursery log, and workers who will be affected should be informed.

A stock of spare parts should be kept of those items whose 

function is critical, that need regular replacement, are hard to find, 

or take a long time to get. Those items that may be needed in an 

emergency should be labeled to indicate where they go or what 

they fit. As these items are used, they must be restocked promptly.

Because the nursery manager cannot be available all of the time, 

more than one person should know what to do in an emergency. 

The following tips should be discussed with all responsible 

personnel and documented in the nursery operating manual:

1. What conditions are normal—This is necessary to 

recognize an abnormal situation that requires correction. 

2. What conditions require immediate attention and what 

can wait—No one likes to be called out of bed in the middle 

of the night to fix something that could have waited until 

morning, but it is worse to be complacent about something 

that should be fixed immediately. 

3. How to fix what is wrong—Everyone involved should be 

familiar with critical nursery repair procedures.

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4. Where the tools and spare parts are kept—Tools and

spare parts should always be kept in the same place, always 

be in their place, and be where someone can get to them 

quickly. When there is a crisis, nothing is more exasperating 

and time wasting than having to hunt for tools and parts. 

5. Who to call if help is needed—Emergency phone numbers 

should be posted in the headhouse or other central location, 

including those for the electrician and other service 

personnel. It may also be useful to list the numbers of local 

growers who may be able to help, pest specialists, and 

nursery consultants.

Use all of your senses all of the time. Many potential problems 

can be averted by staying alert. When approaching a propagation 

structure, make a conscious effort to observe if things are normal. 

On a warm sunny afternoon, fans should be running. On a cold 

day, the furnaces should be on and perhaps the vapors from the 

flue pipe visible. If they are not, investigate. Is the double layer of 

plastic inflated and firm, or flapping loose? If it is loose, check the 

inflation blower. If the blower is running properly, check for holes in 

the covering. If the plastic is too tight, reduce the opening into the 

blower or blower speed. If you are visiting the structure at night, 

notice if the photoperiod lights come on when they should. If it is 

during the hardening phase, when the lights should be off, note 

whether any lights were left on near the propagation structure.

Make it a point to visit the growing areas on your way from one 

place to another, just to walk through. As soon as you enter, your 

senses will tell you if temperature and humidity are within a 

reasonable range. Listen as you walk through the nursery. Does 

any running motor squeak like it needs oiling? Do you hear the 

hum of a running motor, but nothing is turning? Look for a broken 

belt or a stalled and overheating motor. Loose or worn belts may 

be noisy and should be fixed so you can hear the sounds of other 

problems. Do you hear water running? Should it be running? Is the 

furnace running smoothly, or is combustion pulsing or uneven? 

Carbon dioxide generators make a high-pitched sound that is 

normal.
Use your nose. Does the air in the propagation structure smell as it 

should? Is the furnace properly tuned, or is combustion not 

complete? Has the house just been fumigated? If so, are the 

warning signs posted on the doors? Most nursery chemicals can 

be identified by their characteristic odor. Likewise, overheated or 

arcing motors have a distinctive smell. Some experienced growers 

are even able to detect the faint smell of gray mold, and so may be 

able to avert a disease outbreak.

Examine the seedlings closely. Is the morphology of the shoot 

correct and normal for their current stage of growth? In particular, 

watch for signs of premature bud set. Any signs of nutrient 

deficiencies or toxicities? Pick up a tray or block container. Does 

the weight feel about right? Is the root plug moisture at or close to 

field capacity? Are the roots healthy, or is there evidence of root 

rot? Is the foliage healthy, or are there signs of abnormal 

symptoms? Are insects present (on hardwoods look on the 

underside of the leaf)? If a problem develops later, it helps to know 

what potential pests have been in the growing area so that control 

treatment can be started immediately.

Each nursery is a little different, and it is hard to be specific about 

everything to look for. Nursery managers should make a checklist 

to use as a training aid to teach their staff how to be alert and 

what to look for, but there is no substitute for direct experience.

Be alert to problem development. The sooner an abnormal 

condition is recognized, the more time there is to correct it before 

any damage is done. The key is knowing what constitutes the 

normal condition and being alert enough to recognize when 

something is out of place. Alarm devices can be very useful to call 

for help when no one is present. There should be a checklist

posted in the headhouse or other central location indicating what 

the environmental control settings are, the condition of the crop, 

and other information necessary to help diagnose an abnormal 

situation.

Keeping a daily diary or log is also a good idea. It will help 

determine what is normal, and where there are departures from 

normal, it may give clues as to what is wrong. Check the 

hygrothermograph, environmental

control computers, and other monitoring equipment regularly (at 

least daily) and record observations in the daily log. Weekly 

reviews of the log may help detect subtle problems or changes. 

Computer-based expert systems are now available that will not 

only collect and display the data, but analyze it and tell the grower 

when a problem occurs, and even predict future problems and 

recommend solutions.

The following examples demonstrate how hygrothermograph 

charts or computer data records can be used to solve problems:

• The charts indicate that, although temperature control is 

satisfactory in the morning and late afternoon, it exceeds 

the setpoint during the hottest part of the day. This trend 

indicates inadequate cooling capacity. Check all fans, 

evaporation pads, water pump, and vents for proper operation. 

If everything is working properly, then perhaps you are 

experiencing one of those few days of the year when the heat 

load exceeds the design capacity of the cooling system. If it 

happens frequently, the cooling system is not adequately 

designed or the climate is too humid for evaporative cooling to 

be efficient.

• On a sunny day, the records show an abrupt rise in 

greenhouse temperature. The most frequent cause is a power 

failure. On hot sunny days, these peak temperatures can be very 

damaging and call for immediate action (see section 1.5.5.2). 

Excessive temperature should trigger an alarm that will summon 

help but, without the temperature records, it would be impossible 

to determine whether damaging temperatures were reached and 

for how long.

• The temperature falls well below the setpoint before the 

heater comes on. This pattern is typical of a malfunctioning 

temperature sensor such as a sticking thermostat. This usually 

occurs at the very beginning of the heating period and tends to 

be self-correcting, but if it occurs repeatedly, the thermostat 

must be replaced.

• Temperatures fluctuate widely around the setpoint. This can 

be caused by several things. Are the temperature sensors in 

direct line with the heater or is heat circulation blocked in some 

way? If so, the sensors must be moved and the circulation 

problem corrected. This pattern can also be caused by a 

thermostat with too great a differential, either because it is 

improperly set or because it is wearing out. The thermostat must 

be readjusted or replaced.

171
Desiccation injury. In open growing compounds or shadehouses, 

physically covering the seedlings may be the best option for 

avoiding desiccation injury. Probably the cheapest covering that 

can be deployed quickly is polyethylene, preferably white, but clear 

or black will do in an emergency. Other, more effective plastic mesh 

coverings are also available, but they are more expensive. After the 

temperature has risen above the damage threshold, the covering 

should be removed promptly, especially in direct sunshine, because 

overheating can become a problem.

Covering the seedlings can also protect against cold injury, 

especially if insulated foam plastic sheets are used.

Frost protection with irrigation. Because water releases heat as 

it freezes, succulent seedlings can be protected from cold injury 

with irrigation under certain conditions. First, the need for 

protection depends on the seedlings' cold hardiness, which 

gradually increases during the late summer and fall as the crop 

goes into dormancy (fig. 1.5.10A). The dehardening curve in the 

late winter and early spring is much steeper, however, because 

plants lose their hardiness as soon as temperatures begin to 

warm. Therefore, before frost protection with irrigation is begun, 

the nursery manager should have an idea of how cold hardy the 

seedlings are. A well-designed growing schedule will allow time for 

an adequate hardening period and periodic cold hardiness tests 

can show how much cold the crops can tolerate at the moment 

and the rate at which they are hardening. The weather station at 

the nursery should be correlated with the local official weather 

station so that minimum temperatures at the nursery can be 

predicted from local forecasts. If the predicted minimum 

temperature is below the damage threshold for seedlings, then 

frost protection is warranted.

The next requirement is a proper irrigation system. A system 

designed for providing normal irrigation water demand may not be 

adequate for frost protection. An irrigation system designed for 

frost protection must supply a uniform, almost continuous film of 

water to the seedling foliage because the protection exists only as 

long as water continues to freeze and release heat. Boom 

irrigation systems may not move fast enough, and ice buildup 

would be a problem. Sprinkler irrigation systems designed to 

provide frost protection should include the following 

considerations (Pair and others 1983):

1.5.5.2 Temperature crises

When the temperature becomes either too hot or too cold, 

succulent seedlings can be damaged within a very short time and 

so immediate action is required. Even in fully controlled 

propagation structures, failure of environmental control equipment 

for just a short period of time can cause seedling injury (fig. 1.5.9). 

Because emergency measures are sometimes damaging in 

themselves, the nursery manager must decide in each instance 

how fast to react and what actions represent the best alternative.

Unusual cold. There are two types of winter injury. When the 

temperature falls below the seedlings' cold tolerance, the 

resulting injury is from low temperature. When the tops of 

seedlings are exposed while the root systems are continuously 

frozen, the resulting injury is from desiccation. Nursery 

managers must determine which type of cold injury is most 

threatening because the type of response can be different.

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Even with the proper irrigation system, the nursery 

manager must know when to start applying water for 

frost protection. Weather measurements with a psychrometer (wet bulb and dry bulb temperatures) are 

absolutely essential. The wet bulb temperature is 

important because, under low relative humidity 

conditions, the evaporative cooling effect can actually 

drive plant temperature lower than the air temperature 

when water first contacts the plant tissue (fig. 1.5.1 OB). 

Wind can cause the same effect, and so knowledge of 

wind speed must also be factored into the decision 

making process. Nursery managers who anticipate 

using irrigation for frost protection should become better 

informed by reading technical literature, for example, 

Began (1988) and section 4.2.7.4 in volume four of this 

series.

173

1. Sprinkler nozzles should have relatively smalldiameter orifices, ranging from 1.6 to 4.8 mm (1/16 to 

3/16 in).

2. Metal sprinklers are generally preferred because of the 

tendency for ice to build up on plastic heads.

3. The sprinkler heads should rotate at least one 

revolution per minute.

4. Sprinklers should not be spaced any further than 50% 

of their effective diameter.

5. Irrigation application rates of 2.5 mm (0.1 in) per hour 

have been effective under low wind conditions. At this 

rate, about 421 liters/min of water is required to cover 

1 hectare of seedlings (= 45 gal/min ac).
• Vents stuck open-Close them manually and then oil 

them. Check for stuck thermostat or the wrong setting.

• Hole in propagation structure covering-Patch or

cover seedlings with plastic.

If the heating system cannot be repaired quickly, then 

portable heaters must be moved into the propagation 

structure. Propane heaters should be used if possible 

because oil-burning models produce fumes that are 

toxic to both humans and plants.

Excessive heat. Unusually hot weather can cause heat 

injury in open compounds but the situation is particularly 

critical in propagation structures, especially in the spring 

when solar input is high and when young seedlings are 

succulent (fig. 1.5.11A). High heat levels can cause both 

direct and indirect injury. Intense sunlight can injure 

seedling stem tissue (fig. 1.5.11 B), and the resultant 

heat also increases transpirational losses, which can 

lead to indirect drought injury. (See section 5.1.5.3 in 

volume five of this series for symptoms and help in 

diagnosis.)

Excessive heat during the rapid growth phase is a 

relatively simple problem because immediate irrigation 

produces transpirational cooling, especially in lowhumidity climates. The risk of damage from emergency 

irrigation is low, although some fertilizer may be leached 

out of the growing medium. Unseasonally warm 

temperatures are a more serious problem during the 

hardening phase or in unsheltered storage, however, 

because seedling dormancy may be affected. In the fall, 

temperatures above 10 °C (50 °F) can delay and 

possibly reverse hardening. In the late winter and 

spring, temperatures above 5 °C (40 °F) are likely to 

cause irreversible dehardening. Generally, these 

unseasonal episodes do not last long enough to cause 

problems, but if loss of seedling dormancy in the spring 

is a chronic problem, then refrigerated storage is the 

best solution.

An overheated greenhouse demands prompt action. The 

usual cause is a cooling system failure, and 

temperatures on a hot sunny day can rise at the rate of 1 

°C (0.5 °F) per minute. Manually open all of the doors 

and vents in propagation structures. In a small structure, 

this can be quite effective, but it is of limited value in a 

large one. If a power outage has occurred, shut off 

everything that is not essential and switch to the 

emergency generator. If that is not the problem, check 

thermostats to be sure they are set correctly and 

working. Reset or replace as needed. Failure of only part 

of the cooling system

This is a good example of how the proper information, 

experience, and equipment are necessary to respond to 

crises. The inexperienced nursery manager who turns 

on the irrigation system for frost protection without 

having the necessary information can actually cause 

more damage than if nothing were done. (Symptoms 

and management of cold injury are covered in section 

5.1.6 of volume five, and cold hardiness testing will be 

discussed in volume six.)

Heater failure. When it is very cold outside and the 

heating system fails, temperatures in a double-wall 

polyethylene greenhouse can fall at the rate of 0.5 °C (1 

°F) per minute. This allows only 20 minutes between 10 

°C (50 °F), which is a typical alarm temperature setting, 

and freezing. If the plant material is succulent, immediate 

action is required because even if the seedlings survive 

freezing, they may be thrown into irreversible dormancy. 

Much depends on the relative hardiness of the crop. If 

the seedlings have begun the hardening process, the 

potential for imposing dormancy is immaterial and, if the 

freeze occurs late in the hardening process, usually no 

harm is done.

First, locate the cause of lack of heat. If it will take long 

to correct, prepare to apply emergency heat. Look for 

the simple things first:

• Power failure-If all of the power is off, shut off 

everything that is not essential in order not to 

overload the generator, and then start the 

emergency generator.

• Heater off-Check the fuel supply first. If it is 

adequate, check the furnace as the pilot light may be 

out. Relight it. If it will not stay lit, replace the 

burned-out temperature sensor. If the fan is not 

running, check the circuit breaker and press the reset 

button. If the fan does not start, turn off the circuit 

breaker, smell the motor, and turn the fan blades by 

hand. If the motor smells burnt or the fan will not turn, 

try oiling the bearings and turning the blades. If it still 

will not start, replace the motor. If the motor runs but 

there is little or no air flow, tighten or replace the belts. 

If it is direct drive, check set screws on the shaft. If it is 

an oil furnace that is off, push the reset button. If it 

fails to start, check the circuit breaker and motors as 

above. If it starts but will not stay lit, clean or replace 

the electric eye, faulty stack switch, or high limit 

sensor.

• Cooling fan on-Check for a stuck thermostat or the 

wrong setting. Shut fan off at circuit breaker if 

necessary.

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1.5.5.3 Fire

Although container nurseries are generally low-hazard areas, fires 

can be devastating in propagation structures and other nursery 

buildings. Wood frame structures and those covered with fiberglass 

are particularly susceptible (Hanan and others 1978). If a 

wooden-framed double-poly greenhouse burns, heat builds up near 

the roof, the plastic melts, opens a hole, and releases the heat, so 

that the fires does not spread rapidly. In contrast, a fiberglass 

greenhouse is strong enough to hold the heat until the whole 

structure is on fire. Once fiberglass reaches its decomposition 

temperature, the fire spreads rapidly.

The immediate response should be to turn on the irrigation and turn 

off all nonessential electricity in the vicinity of the fire, especially the 

cooling system. Otherwise, the cooling fans will come on in 

response to the rise in temperature and quickly spread the fire 

throughout the house. Properly located and labeled disconnect 

switches for the fans would be a good precaution. Unfortunately, 

most fires in the propagation structure are above what would be 

wetted by the irrigation system but irrigating may still save part of 

the crop. Most containers are made of polystyrene or polyethylene 

plastic, both of which burn vigorously once ignited and so the 

potential fire hazard should be kept in mind where the empty 

containers are stored. Regular fire inspections and fire drills should 

be a part of every nursery's safety program (Hanan and others 

1978).

1.5.5.4 Water crises

Flooding. Properly located facilities should not be subject to 

flooding from natural causes. However, if a flood can be 

anticipated, shut off all electrical equipment in the nursery and 

move equipment and anything

175

Usually does not result in a crisis, but it should still be corrected 

promptly. This also illustrates the value of redundancy designed 

into the system. If there is only one fan and it fails, the whole 

cooling system is down. If there are three fans and one fails, twothirds of the system is still operating.
else that could be damaged. If there is enough time, the perimeter 

of the nursery can be diked and then bailed; if not, about all that 

can be done is to wait for the water to subside, and then clean up.

Internal flooding is usually caused by a broken water line. 

Immediately shut off the water main and then repair the break. 

Flooding and its adverse consequences can be minimized and 

repair work simplified by dividing up the water system with 

strategically located valves that are labeled and easy to reach. 

Then, if an irrigation line breaks, it can be shut off without affecting 

the water supply to the rest of the nursery, especially to critical 

uses such as the evaporative cooling system.

Lack of water. A complete loss of water pressure can be caused 

by pump problems, or some other catastrophe with the water 

supply system. When water lines break or pumps quit working, the 

problem and its solution immediately become apparent. Another 

possibility is a malfunction of the automatic irrigation controller. 

Depending on container size and ambient weather conditions, 

seedlings can do without irrigation for a few hours except when 

water is needed immediately during a temperature crisis. If there is 

water available in the greenhouse but no way to apply it 

automatically, then the seedlings can be watered by hand. 

Emergency phone numbers for plumbers, electricians, and pump 

specialists should be posted in the headhouse or other easily 

accessible location.

Irregular seedling growth patterns due to uneven distribution of 

water are common but can be difficult to diagnose. Although 

usually caused by a poorly designed irrigation system, even the 

best systems must be watched for plugged or malfunctioning 

sprinklers. (Monitoring the water in containers is discussed in 

section 4.2.6 and tests of irrigation efficiency systems are covered 

in section 4.2.3.5 of volume four of this series.)

1.5.5.5 Cultural problems

In contrast to equipment malfunction or severe weather, cultural 

problems develop more slowly, require closer observation to detect 

at an early stage, and rarely require immediate attention. However, 

cultural problems are just as important, and it is often harder to find 

their cause and correct them. In most cases, however, they can be 

prevented with a proper scheduling and cultural tech

176

piques. The following discussion is intended to help nursery 

managers diagnose the cause of cultural problems. (A more 

detailed stepwise diagnosis procedure and damage keys can 

be found in volume five of this series.)

Delayed or erratic germination. Seed dormancy problems 

often occur in a random pattern, with seedlings of various sizes 

interspersed with empty cells (fig. 1.5.12). Germination problems 

must be identified and corrected promptly or valuable production 

area will be lost for the rest of the crop cycle.

Germination tests can give the nursery manager an idea of what 

the germination rate and total germination should be for a 

particular seed lot. These tests can be performed by seed testing 

laboratories for a fee, or they can be conducted at the nursery. If 

time is available before operational sowing, a simple test can be 

run in which a series of containers can be sown with one to 

several seeds per cavity. The speed of emergence and the 

proper seed sowing density can be determined for each seed lot 

or species within a month.

Regardless of species, seedling emergence should be evident in 

operational sowings within 4 weeks if the seed has been tested 

and found viable, given the appropriate pregermination treatment, 

and if good sanitation procedures are followed. If emergence is 

slow or absent after several weeks, scrape some of the seed 

covering away gently and look for seeds. Missing seed indicates a 

seeder problem or animal predation. (See section 5.1.3 in volume 

five of this series.) Remove a few seeds, cut them in half, and 

examine with a hand lens. If the interior tissues are dark, then 

fungal decay is a possibility; if they are cream-colored and 

otherwise healthy, then a seed dormancy problem exists. Check 

recommended germination temperature against current 

temperature records. Examine the depth of the seed covering. If 

too deep, remove some of the seed covering; if too shallow, 

increase irrigation frequency.

In the case of partial germination, resowing or transplanting 

may be justified if the projected number of empty cells is 

greater than the oversowing factor. This must be done 

immediately, however, because resown seedlings or 

transplants may be overtopped and suppressed by their 

neighbors.
Growth rate behind schedule. In spite of the best efforts 

to control growing conditions, weather differences from 

one year to the next will cause a corresponding variation 

in crop growth. Periodic measurements of rate of 

germination, seedling size, budset, and cold hardiness are 

important to compare one crop with the next. By 

developing a baseline of growth and development as a 

function of time, the growth of subsequent crops can be 

more accurately predicted. Previous growth records are 

invaluable in identifying and correcting growth problems 

(fig. 1.5.5A). The earlier a potential problem can be 

detected, the easier it is to correct it.

Be aware that seeds of the same species but from 

different sources can exhibit radically different growth 

patterns and may have to be cultured entirely differently. 

Species with wide geographic distributions, such as 

Douglas-fir [(Pseudotsuga menziesii (Mirb.) Franco] and 

ponderosa pine (Pinus ponderosa Dougl. ex Laws.), 

contain ecotypes that may react more like different 

species than seedlings of the same genus. For example, 

high-elevation Douglas-fir seedlings from Montana will 

grow much more slowly and set bud earlier than the

same species from a coastal Washington seed source (fig. 

1.5.13A). Coastal ecotypes can be grown without 

photoperiod lighting, whereas those from interior, highelevation sources will set bud soon after germination 

without proper photoperiod control. A fertilization trial with 

six seed sources of Douglas-fir (fig. 1.5.1313) showed that 

coastal Washington sources could be grown to target 

height specifications with only 100 ppm nitrogen (N), 

whereas more interior sources from eastern Washington, 

Idaho, and Montana generally required at least 150 ppm N 

(Thompson 1994).

Premature dormancy. Seedlings that set terminal buds 

and stop shoot growth prematurely typically occur in an 

irregular pattern, and often bud set may be sudden (fig. 

1.5.14A). Dormancy problems are usually a response to 

some environmental stress, so the first step is to check all 

of the environmental controls for proper setting and 

function. Examine hygrothermograph charts, computer 

weather records, and daily operating log for equipment 

malfunctions, abnormal weather events, or improper 

cultural procedures. If a specific cause can be found, 

correct the problem as quickly as possible, but often

177
seedlings that have gone into premature dormancy are 

difficult to stimulate back to normal growth rates or the 

response may be variable (fig. 1.5.14B). If the cause is 

unknown, the following procedures can be tried in 

sequence:

1. Increase the photoperiod light intensity at night to 10 

μmol/m2/sec (650 lux) and the duration of the light 

intervals to a ratio of 1 light period out of every 8 dark 

periods (see section 3.3.4 in volume three, chapter 3 

of this series for more detailed information). 

2. Increase the night temperature to 22 to 24 °C (72 to 

75 °F).

3. Raise the nitrogen level in the nutrient solution. Most 

species can tolerate 300 ppm without adverse effects.

4. Spray with 50 ppm gibberellic acid.

178
If none of these emergency measures works, then managers are 

left with either accepting a smaller seedling or allowing the crop 

to go through the dormancy cycle and shipping it with the next 

crop.

Foliar symptoms. Abnormal foliage color can be caused by 

several different problems. Nursery managers should examine the 

seedling roots first, because many foliar symptoms are caused by 

root problems.

Wilting. Wilting is caused by the inability of the roots to replace 

moisture in the plant as fast as the foliage is losing it. The most 

common cause is lack of moisture in the root plug. If this is the 

case, the seedlings must be watered immediately. Sometimes 

wilting will occur on unseasonably hot, sunny days in otherwise 

healthy, well watered seedlings, especially after periods of cool 

cloudy weather. If this is the case, try increasing the humidity and 

decreasing peak day temperatures by brief bursts of irrigation. If the 

condition persists, then the irrigation procedures or schedule may 

have to be adjusted.

Wilting can also indicate problems with water uptake by the root 

system. A growing medium that is too fine or has been over 

compacted will have low aeration porosity and can easily become 

waterlogged. A waterlogged growing medium often promotes root 

rot. Under these conditions, wilting is often accompanied by 

chlorosis and stunted growth, which may be in a block pattern (see 

following sections). The only solution is to reduce the amount of 

irrigation at each watering, applying just enough water each time to 

force leachate out the bottom of the containers. The irrigation 

scheduling should also be adjusted, and the growing medium 

problem corrected during the next crop. (Growing media are 

discussed in volume two, and proper irrigation practices covered in 

volume four of this series.)

Chlorosis. Chlorosis is a reduction in the amount of 

chlorophyll present in the foliage and is a general symptom of 

many maladies. Careful observation of where the symptoms 

occur can yield important clues.

Chlorosis is a symptom of several mineral nutrient deficiencies 

including nitrogen, iron, magnesium, and sulfur, but the first two 

are the most common in container nurseries (fig. 1.5.15A). An 

examination of the symptom pattern, both on the seedling 

foliage and within the growing area, may be diagnostic (fig. 

1.5.15B). If the damage is general or concentrated on the older 

foliage and is accompanied by stunting,

179

suspect nitrogen deficiency. Iron deficiency symptoms are different 

in that only the new foliage is chlorotic. To confirm the diagnosis, 

check the pH and formulation of the nutrient solution and also 

check the pH of the growing medium. If an iron deficiency is 

suspected, pay particular attention to the pH levels and make sure 

that
iron chelate fertilizers are being used. Chemical analyses 

of some symptomatic foliage are sometimes helpful, 

especially if they are compared to tests of healthy tissue. 

Compare the foliar nutrient levels to established 

standards. One quick check of the diagnosis is to apply a 

foliar fertilizer of the suspected deficient nutrient and 

observe whether the symptoms disappear within a week 

or two. (Mineral nutrient deficiency symptoms, foliage 

nutrient standards, and proper fertilization techniques are 

provided in volume four of this series.)

Spots. Chlorotic or necrotic spots on the seedling foliage 

or stem can be caused by several problems. Foliar spots 

can be caused by fungi, bacteria, and insects, and so 

these possibilities should be discounted first (see following 

section). Deficiencies of magnesium and calcium, and 

toxic levels of boron can be responsible, and managers 

should follow the advice in the previous section. If only the 

tips or margins of the foliage are chlorotic and particularly 

if necrotic tissue is present, then chemical damage should 

be suspected. Salt injury or pesticide damage can also 

cause these symptoms. Check the electrical conductivity 

level of the irrigation water first, then within the growing 

medium and from leachate. Air pollution is also a 

possibility but this should have been investigated during 

site selection. If the source of pollution is within the nursery 

itself, it can be eliminated. Sulfur dioxide is produced by 

burning high-sulfur fuels and the exhaust gases must be 

vented well away from the greenhouse. Check with the 

fuel supplier and if the carbon-to-sulfur ratio is less than 

10,000:1, switch to a low-sulfur fuel. If an oil-burning space 

heater must be used for emergency heat, use kerosene or 

number 1 diesel oil. Another source of internal air pollution 

is ozone. Electric motors that are dirty or badly worn will 

arc excessively and generate appreciable quantities of 

ozone. Clean or repair the motors if this condition is found. 

(Proper fuel selection is discussed in section 3.1.4 in 

volume three, and air pollution symptoms discussed in 

5.1.5.3 of volume five of this series.)

Determining the exact cause of cultural problems requires 

careful analysis and so inexperienced managers should 

consult with a nursery specialist.

Abnormal growth patterns. An important key to 

diagnosing cultural problems is to observe the spatial 

pattern in which the growth problem occurs.

180

Edge or breadloaf effect. Height growth is typically 

greater in the middle than it is at the edges of a bench or 

section of seedlings, and in extreme cases, the seedlings 

along the edge are also chlorotic (fig. 1.5.16). If this 

pattern is pronounced, a profile view looks like a loaf of 

bread. The most common cause is inadequate air 

circulation, which causes localized differences in 

temperature and humidity. The cure is to have positive air 

circulation, especially during daylight hours and preferably 

under the bench. Another cause is that the containers at 

the edge of the bench are exposed to more light. This 

accelerates drying and may cause above-optimum root 

temperatures. The problem can be minimized by using 

white or light- colored containers. Styrofoam® containers 

are advantageous in this respect because of their 

insulating as well as light-reflecting qualities. Watering 

should be programmed to maintain adequate moisture in 

those edge containers subject to the most rapid drying. 

This means that the growing medium must be porous 

enough so the interior containers can tolerate the excess 

moisture they will receive. Maintenance of adequate 

humidity will also reduce the difference in water 

consumption between edge and interior cavities.
Rings or streaks. Chlorotic or stunted seedlings grouped in rings, 

circles, or streaks often indicate problems with irrigation uniformity. 

The watering pattern should be tested with a fixed grid of cups to 

determine whether the symp tomatic seedlings are getting more or 

less water than the rest of the house. The situation can be 

compounded by high-salinity irrigation water or a growing medium 

composed of particles that are too fine in texture; in either case, 

the tolerance of the seedlings to water availability problems is 

reduced. The best solution is to redesign the irrigation system to 

provide more uniform water distribution. It may be possible to 

simply change to a nozzle that has better performance for the 

existing water pressure and spatial distribution. If this is 

impractical, a short-term solution is to hand-water the areas that 

are not getting enough. Or, if excess water runoff is not a problem, 

a coarse well-drained growing medium can be used and the 

duration of irrigation increased to make certain that all areas 

receive the proper amount of water. (Typical symptoms are 

illustrated in fig. 4.2.24, and proper irrigation system design is 

discussed in section 4.2.5 of volume four of this series.)

If the symptomatic seedlings vary in size and bud condition (fig. 

1.5.14B), then the problem could be variable light intensity from the 

photoperiod light system. Seedlings that do not receive enough 

light intensity during the night can stop growing and set bud 

prematurely. This problem is particularly common with obliquely 

mounted light systems or overhead lamps of the wrong type or 

wattage. It may also only be obvious with certain species or seed 

lots, particularly those from high elevations or latitudes. The 

problem can be diagnosed by visiting the propagation area at night 

and measuring the light intensity in a grid pattern throughout the 

growing area. It may be possible to correct the problem by 

changing lamps; in extreme cases, however, the entire lighting 

system will have to be redesigned. (The symptoms are illustrated in 

figure 3.3.12, and the proper photoperiod lighting system design is 

discussed in section 3.3.4.5 of volume three in this series.)

Strips of symptomatic seedlings can also be caused by design 

problems in the growing area. For example, a bench that does not 

allow proper air pruning of the root system can cause irregular 

growth and even lead to root disease problems (fig. 1.5.15B).

Block pattern. If seedlings are completely absent from certain 

blocks of containers, suspect a sowing problem. Abnormal 

seedling growth patterns that vary between different blocks of 

containers can usually be traced to problems with the growing 

medium (fig. 1.5.17A). The problem can be either differences in 

porosity, uneven incorporation of chemical amendments, or poor 

container sterilization. The former can be caused by poor quality 

media or sloppy container-filling technique, especially if the 

containers are filled by hand. Some workers have a tendency to 

pack the growing media too tightly in the cells, causing porosity 

problems. Incorporation of slow-release fertilizer or other 

amendments can also cause differences in seedling growth 

between blocks of containers. For example, if too much dolomite 

has been incorporated into the growing medium of certain blocks, 

their seedlings will exhibit chlorosis or twisted needles (fig. 

1.5.17B). These symptoms may be more common with certain 

species than others (Dumroese and others 1990). Another block 

pattern can be traced to older containers that have not been 

properly sterilized. Many root rot pathogens build up on residual 

growing media or roots that remain in the cells of the containers 

and infect the subsequent crop. This pattern can be particularly 

evident when crops are sown in a mixture of new and used 

containers. Better seedling growth in the new containers indicates 

a sterilization problem. (Growing media formulation is discussed in 

volume two, and container sterilization in section 5.1.7.2 of volume 

five of this series).

Mosaic pattern. A mosaic seedling growth pattern is one in which 

patches of normal seedlings are growing interspersed with patches 

of chlorotic, stunted, or otherwise abnormal seedlings. This 

syndrome is different from other abnormal growth patterns in that 

the patches of seedlings are relatively small in size and the pattern 

does not coincide with any obvious condition. One of the most 

common causes of mosaic growth patterns is uneven invasion of 

mycorrhizal fungi; this is commonly seen in bareroot nurseries, 

especially with crops th at require vesicular-arbuscular mycorrhizae. 

Lack of mycorrhizae should not be a problem in container nurseries 

using the proper growing media and providing adequate 

fertilization, however.

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182
A more common cause of mosaic growth patterns in container 

seedlings can be caused by irrigation water that is high in pH or in 

soluble salts. Either of these conditions should have been detected 

during site selection but salts can also build up in the growing 

medium under poor irrigation practices. Often the seedlings are 

chlorotic; in the case of iron deficiency, the younger foliage is yellow 

while the older foliage remains green (fig. 1.5.18A). The situation 

can be easily remedied with special chelate fertilizers and by 

making certain that enough water is applied each irrigation so that 

the soluble salts leach down and out of the container (fig. 1.5.18B).

Random pattern. Sometimes, single seedlings that are distributed 

randomly throughout the propagation area exhibit disease 

symptoms or some type of abnormal growth (fig. 1.5.19A). Random 

distribution growth patterns are often caused by seed problems, 

and these can be either genetic or pathogenic in nature. For 

example, white albino germinants are occasionally found scattered 

randomly in some seed lots (fig. 1.5.19B). Seed-borne pathogens 

also affect random individuals and some seed lots are affected 

more than others. Because insects are highly mobile and often only 

attack one seedling at a time, insect damage is often found to be 

randomly distributed throughout the propagation area (fig. 

1.5.19C).

Pest problems. The ideal propagation environment in 

container nurseries also leads to problems with pests, including 

fungal pathogens and insects.

Pest exclusion is one of the benefits of growing seedlings in sterile 

growing media and containers because all of the common fungal 

problems associated with native soil are eliminated. Fungi can be 

introduced on dirty containers and seed coats and through the 

irrigation water, however. Container nursery managers must remain 

particularly vigilant because the ideal propagation environment is 

also conducive to fungal growth. The mycelia or fruiting bodies of a 

fungus are sometimes visible on necrotic parts of the seedling, and 

these signs are necessary for the proper diagnosis and 

subsequent treatment of a disease. Growers must be able to 

distinguish between pathogenic and beneficial fungi, however. The 

fruiting bodies of mycorrhizal fungi can sometimes be seen on or in 

containers (fig. 1.5.20A), and some types of mycorrhizae can be 

seen on the seedling root system (fig. 1 .5.20B). Root rots can be 

diagnosed by stripping away the outer cortex and looking for white

healthy tissue; brown roots indicate disease (fig. 1.5.20C). 

Samples should be collected and sent to nursery pest specialist 

for culture and identification. Disease outbreaks can be 

suppressed with fungicides by preventing the fungus from 

spreading to healthy tissue, but they should not be expected to 

cure seedlings that have already been injured.

The growing area should be inspected regularly for the presence 

of insects. Do not wait for damage symptoms to appear. Insect 

damage often occurs near the perimeter of the propagation area, 

or at other times in a random pattern (fig. 1.5.19A&C). Examine 

the foliage thoroughly; some insects are so small and so well 

camouflaged that they can easily be missed. Insect pests are also 

mobile and many hide during daylight hours, and so the 

propagation area should occasionally be inspected at night. 

Yellow or blue sticky cards and pheromone traps can help detect 

the presence and population levels of some insect pests. Proper 

identification is important; for example, harmless shore flies are 

almost identical to harmful fungus gnats. The frequency of 

inspection and the urgency of action depends on the stage of 

growth and the nature of the probable pest. For instance, sucking 

or chewing insects are serious pests of broadleaf seedlings during 

the rapid growth phase but are of less consequence during the 

hardening phase when the leaves are about to abscise anyway.

Diagnosing nursery pest problems requires experience as well as 

the proper knowledge and so new nursery managers should 

contact surrounding nurseries to see if they have had similar 

problems, or contact a professional nursery pest specialist. (See 

section 5.1.2 in volume five of this series for more help in pest 

diagnosis.)

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184
185
1.5.6 Customer Relations

The importance of good customer relations cannot be

overemphasized. The old adage "the customer is always right" 

should be part of the management philosophy of any nursery. Keep 

your customers involved in the development of the crop. If 

germination rates are low for a particular seed lot, notify the 

customer immediately because it may be possible to resow or 

otherwise correct the problem. Slow seedling growth, pest damage, 

or any cultural problem that will delay seedling delivery, affect the 

number of shippable seedlings, or that may require adjusting the 

grading standards should also be discussed with the customer 

when they are first noticed. There is nothing more irritating to a 

customer than unpleasant surprises at delivery time. By then, 

customers have already made a major investment in site 

preparation and plans for outplanting that may be lost if the proper 

number or quality of seedlings changes. Customers will be more 

understanding and sympathetic to major problems if they are kept 

informed of the condition of their seedlings throughout the growing 

cycle. Then, they will have time to adjust their planting programs. 

Inviting clients to view their seedlings is a good way to make them 

more knowledgeable about nursery culture, and also is a good time 

to discuss crop development and seedling grading standards. The 

key is to give everyone involved as much lead time as possible to 

make the necessary adjustments. There is plenty of competition in 

the container tree nursery business and frustrated customers may 

just decide to go elsewhere for their seedlings.

186
1.5.7 Summary

The final aspect of nursery development involves setting up the 

management system. There are several key aspects of every 

successful nursery: solid organization, professional personnel, a 

system of data collection and analysis, and an established system 

for solving problems. The management of a nursery must have a 

structured organization if it is to succeed, which ensures that 

responsibilities are assigned and that jobs get done. In small 

nurseries, the manager may also be the owner and may also 

perform all of these functions, but as the nursery increases in size 

and complexity, some of the tasks must be delegated to other 

personnel. Supervision requires special skills and new managers 

must be able to hire and keep good, productive employees. All 

nurseries should have a formal safety program and schedule 

regular safety meetings.

Each nursery should have a system for systematic collection and 

analysis of information of financial and production data as well as 

cultural records, including growing schedules, environmental 

conditions in the propagation area, and crop development 

records. Record keeping systems can be as simple as a daily log 

book or as detailed as a computer system that records and stores 

environmental data. Records of seedling growth rates are 

particularly useful for detecting growth problems early and for 

generating production trends for future crops. Communicating 

with customers is crucial, and the target seedling concept is a 

useful way to describe what type of seedling they expect, and for 

nursery managers to describe what they can realistically produce.

One of the most important aspects of nursery management is 

solving the day-to-day problems. Nursery managers can become 

better problem solvers by visiting other nurseries, attending 

workshops and training sessions, and keeping up with the latest 

published literature. Many crises are caused by equipment failure 

or severe weather, and although the timing of a crisis can never be 

predicted, the frequency of occurrence and the damage done can 

be minimized with proper management. In contrast to equipment 

malfunction or severe weather, cultural problems develop more 

slowly and rarely require immediate attention. However, they can 

usually be prevented with proper scheduling and quick diagnosis.

Finally, nursery managers must always keep in mind that their 

seedlings belong to the customer, who should be kept informed of 

any developments during the growing season. Nurseries must 

involve the customer in critical decisions so that there are no 

surprises at the time of seedling delivery.

187
1.5.8 References

1.5.8.1 General nursery management references

Davidson, H.; Mecklenburg, R.; Peterson, R. 1988. Nursery 

management: administration and culture. Englewood 

Cliffs, NJ: Prentice Hall. 413 p.

Furuta, T. 1978. Environmental plant production and 

marketing. Arcadia, CA: Cox Publishing Co. 232 p.

Hanan, J.J.; Holley, W.D.; Goldsberry, K.L. 1978. Greenhouse 

management. New York: Springer-Verlag. 530 p.

Jozwick, F.X. 1992. The greenhouse and nursery handbook. 

Mills, WY: Andmar Press. 511 p.

Langhans, R.W. 1980. Greenhouse management. Ithaca, NY: 

Halcyon Press. 270 p.

Nelson, P.V. 1991. Greenhouse operation and management. 

Englewood Cliffs, NJ: Prentice Hall. 612 p.

1.5.8.2 Specific literature cited

Armson, K.A.; Sadreika, V. 1979. Forest tree nursery soil 

management and related practices. Ottawa, ON: Ontario 

Ministry of Natural Resources. 179 p.

Brumfield, R.G. 1992. Greenhouse cost accounting: a computer 

program for making management decisions. HortTechnology 

2(3):420-424.

Clements, S.E.; Dominy, S.W.J. 1990. Costs of growing 

containerized seedlings using different schedules at 

Kingsclear, New Brunswick. Northern Journal of Applied 

Forestry 7(2):73-76.

Day, R.J. 1979. The development of a method for monitoring 

the growth of nursery stock. Silv. Rep. 1979-1. Thunder 

Bay, ON: Lakehead University, School of Forestry. 28 p.

Day, R.J. 1981. Programmable calculator (TI-59) programs for 

use in forest nurseries. Silv. Rep. 1981-1. Thunder Bay, 

ON: Lakehead University, School of Forestry. 70 p.

Dumroese, R.K.; Thompson, G.; Wenny, D.L. 1990. 

Lime-amended growing medium causes seedling growth 

distortions. Tree Planters' Notes 41(3):12-17.

Goldsberry, K.L. 1979. Greenhouse safety: for plants and people 

alike. In: Proceedings, Intermountain Nurserymen's Association 

Meeting; 1979 August 1316; Aspen, CO. Ft. Collins, CO: USDA 

Forest Service, Rocky Mountain Station: 14-15.

Hallett, R.D. 1982. Monitoring crop development during the rearing 

of containerized seedlings. In: Scarratt, J.B.; Glerum, C.; 

Plexman, C.A., eds. Proceedings, Canadian Containerized 

Tree Seedling Symposium; 1981 September 14-16; Toronto. 

COJFRC Symp.

188

Proc. O-P-10. Sault Ste. Marie, ON: Canadian Forestry 

Service, Great Lakes Forest Research Centre: 245-253.

Landis, T.D. 1984. Problem solving in forest-tree nurseries with 

emphasis on site problems. In: Duryea, M.L.; Landis, T.D., 

eds. Forest nursery manual: production of bareroot seedlings. 

Boston: Kluwer Academic Publishers: 307-314.

Pair, C.H.; Hinz, W.H.; Frost, K.R.; Sneed, R.E.; Schiltz, T.J. 

1983. Irrigation, 5th ed. Arlington, VA: The Irrigation 

Association. 686 p.

Pawuk, W.L. 1982. The effects on growth of transplanting 

germinating seeds into containers. Tree Planters' Notes 

33(1):38-39.

Began, R. 1988. Sprinkler salvation. American Nurseryman 

168(5):70-77.

Ritchie, G.A. 1984. Assessing seedling quality. In: Duryea, 

M.L.; Landis, T.D., eds. Forest nursery manual: production 

of bareroot seedlings. Boston: Kluwer Academic 

Publishers: 243-259.

Rose, R.; Carlson, W.C.; Morgan, P. 1990. The target seedling 

concept. In: Rose, R.; Campbell, S.J.; Landis, T.D., ed. Target 

seedling symposium: Proceedings, Combined Meeting of the 

Western Forest Nursery Associations. 1990 August 13-17; 

Roseburg, OR. Gen. Tech. Rep. RM-200. Ft. Collins, CO: 

USDA Forest Service, Rocky Mountain Forest and Range 

Experiment Station: 1-8.

Scagel, R.; Bowden, R.; Madill, M. Kooistra, C. 1993. Provincial 

seedling stock type selection and ordering guidelines. Victoria, 

BC: British Columbia Ministry of Forests, Silviculture Branch. 

75 p.

Thompson, G. 1994. Growth of container Douglas-fir at 3 different 

nitrogen fertilization rates. [Manuscript submitted to Tree 

Planters' Notes.] Rochester, WA: Weyerhaeuser Co., 

Rochester Regeneration Center.

Tinus, R.W.; McDonald, S.E. 1979. How to grow tree seedlings in 

containers in greenhouses. Gen. Tech. Rep. RM-60. Ft. Collins,

CO: USDA Forest Service, Rocky Mountain Forest and Range 

Experiment Station. 256 p.

Wallersteiner, U. 1988. Cumulative trauma disorders in forest 

nursery workers. In: Landis, T.D., tech. coord. Proceedings, 

Combined Meeting of the Western Forest Nursery Associations; 

1988 August 8-11; Vernon, BC. Gen. Tech. Rep. RM-167. Ft. 

Collins, CO: USDA Forest Service, Rocky Mountain Forest and 

Range Experiment Station: 75-76.

Wenny, D. 1992. Personal communication. Moscow, ID: University 

of Idaho, Forest Research Nursery.