27
28

Contents

1.2.1 Introduction 29

1.2.2 Critical Site Selection Criteria 30

1.2.2.1 Unobstructed solar access 30

1.2.2.2 Ample supply of high-quality irrigation water 30

Assessing water quality 30

Estimating amount of water use 34

1.2.2.3 Inexpensive and reliable energy source 36

Availability and reliability 36

Quantity required and cost 37

Solar and alternative energy sources 37

1.2.2.4 Adequate land area 37

1.2.2.5 Ecopolitical concerns 38

Land-use zoning and building restrictions 38

Potential chemical pollution 38

1.2.3 Secondary Site Selection Criteria 40

1.2.3.1 Protected microclimate 40

1.2.3.2 Gentle topography 40

1.2.3.3 Seasonal labor supply 41

1.2.3.4 Accessibility 41

1.2.3.5 Distance to markets 42

1.2.4 Evaluation of Alternative Sites 43

1.2.5 Summary 44

1.2.6 Literature Cited 45
1.2.1 Introduction

different propagation structures that must also be matched to the 

site, so a basic knowledge of the types of structures and 

environmenta l control equipment is necessary during site 

evaluation (see chapters 3 and 4 Once the decision has been 

made to build a container tree nursery, the nursery's developer is 

faced with the formidable challenge of selecting a suitable site. Although site selection criteria for a container nursery can be fairly 

restrictive, they are less demanding than those for a bareroot 

facility. Container nurseries can be located on sites that would be 

totally inappropriate for a bareroot nursery because seedlings are 

grown in artificial growing media and with structures and 

equipment to modify the physical environment.

The basic objective of any nursery operation is to modify the 

natural environment so that plants can be produced quickly, 

efficiently, and economically. Container nurseries offer the 

potential for considerable environmental modification, but both 

development and operating costs increase with degree of 

modification. There are a variety of in this volume).

A successful container nursery must be carefully ma tched to the 

environmental conditions on the site; a nursery designed for one 

site will not necessarily be best for another. Therefore, nursery 

developers must analyze the climatic environment at each 

potential site by critically evaluating both short-term and long-term 

weather records as well as through direct observation.

Nursery developers should be prepared to devote a substantial 

amount of time to site selection because many biological and 

operational problems that develop later in nurseries can be traced 

back to problems with the selected site. Nursery sites that are 

selected mainly for economic or political reasons frequently fail to 

meet some of the more critical criteria, and these deficiencies limit 

the success of the nursery. Biological site selection criteria should 

always be paramount, but potential nursery developers must also 

consider business realities.

The things to look for in a potential container nursery site can be 

divided into critical factors and desirable factors (table 1.2.1). 

Critical site selection criteria are those factors that are essential to 

a successful nursery operation. Desirable attributes include those 

site factors that are not absolutely necessary but will increase the 

economy and efficiency of the nursery operation.

29
1.2.2 Critical Site Selection Criteria

1.2.2.1 Unobstructed solar access

Although it should go without saying, container tree nurseries must 

be located on sites with good solar access, both throughout the 

day and during the growing season. It is usually considered 

uneconomical to supply enough light energy for photosynthesis, 

and so container nurseries must be located where they receive full 

sunlight for almost all of the solar day. Any amount of shading will 

decrease productivity and increase costs. This is most critical in 

northern latitudes or in perennially cloudy climates but also applies 

to sunnier locations, because it is relatively easy to provide the 

shading if it is required.

Growing areas must not be affected by shade from surrounding 

trees or buildings. If crops are to be grown year-round, the solar 

angle should be determined for all seasons to ensure that the 

growing area will always receive full sunlight (fig. 1.2.1). Walker 

and Duncan (1974) provide the engineering calculations for determining the shadow length for various latitudes, but Nelson (1991) 

recommends that, as a general rule, greenhouses should be 

located at a distance that is at least 2.5 times the height of any 

object to the east, west, or south. Shelterbelts on the north side 

can be relatively close as long as falling leaves and litter are not a 

problem.

1.2.2.2 Ample supply of high-quality irrigation water

Next to sunlight, a reliable supply of high-quality irrigation water is 

the most important site selection factor. Relatively large amounts 

of water are needed by the seedlings themselves and also for 

regulating the temperature of the growing environment. Container 

seedlings have very low moisture reserves, which are limited by 

the volume of the container and the moistureholding properties of 

the growing medium (Davidson and others 1988), so seedlings 

must be irrigated frequently. In hot climates, water is also essential 

for evaporative cooling. In cooler climates, growers may need to 

use irrigation water during the early spring or late fall for frost 

protection of seedlings in open growing compounds.

Assessing water quality. The definition of water quality is 

determined by its intended use. Water that would be entirely 

suitable for domestic or industrial purposes can be severely 

damaging to plants.

Components of water quality. For nursery site evaluation 

purposes, irrigation water quality is determined by two factors: 

suspended particles (sediments or pests) and dissolved salts.

30
Suspended sediments and pests. Inorganic materials such as clay, 

silt, and even very fine sand particles are small enough to remain 

suspended and so must be mechanically filtered or removed by 

chemical treatments (Tchobanoglous and Schroeder 1985). 

Suspended sediments are abrasive and can quickly wear out water 

pumps, fertilizer injectors, and sprinklers.

The source of the irrigation water determines what types of 

suspended materials it may contain, and typical irrigation sources 

for container nurseries include municipal water, surface water, and 

well water. Municipal water usually has been filtered to remove 

particulate matter, although this should be checked. Surface water 

often contains suspended silt or clay particles, especially after a 

heavy rain, and depending on the characteristics of the aquifer and 

type of casing, even well water may contain sand. Although 

suspended inorganic sediments can be easily removed from a 

potential irrigation source, the costs of water treatment can be 

considerable and so must be factored into the site development 

costs.

Pests can also be suspended in water. Water from surface 

sources, especially ponds in agricultural areas (fig. 1.2.2A), can 

contain propagules of potential nursery pests, which include weed 

seeds and spores of fungi, algae, mosses, and liverworts. 

Specially designed filters can remove the larger pests, including 

weed seeds, algae, and some fungal spores, but the cost of the 

filters increases as the minimum pore size decreases. Domestic 

water sources are normally well filtered and so these pests should 

not be a problem.

Chlorination effectively eliminates pathogenic fungi, bacteria, 

algae, and liverworts. Normal domestic chlorination produces a 

chlorine level of about 1 ppm, which is not injurious to most plants 

(Frink and Bugbee 1987). Irrigation water can also be chlorinated 

at the nursery, but again, this treatment will increase the 

sitedevelopment costs. Fluoride is also added to some domestic 

water sources at the rate of around 1 part per million (ppm) to 

retard tooth decay. Although some ornamental crops have been 

injured by fluoridation (Nelson 1991), plants grown for forestry or 

conservation purposes are apparently more tolerant. 

(Chlorination, filtration, and other potential irrigation water 

treatments are discussed in more detail in volume four of this 

series.)

Dissolved salts. Many different mineral ions can be dissolved in 

potential irrigation water, and even perfectly clear water can contain 

harmful salts. In coastal areas, potential nursery sites can have 

groundwater that is contaminated by saltwater intrusion (Nelson 

1991); in fact, container nurseries have had to be moved further 

inland because of problems with toxic sodium (Na+) and chloride 

(CI-) ions (fig. 1 .2.213). Some cations, such as the calcium (Ca2+) 

and magnesium (Mg2+) ions that are found in "hard" water, can be 

either troublesome or beneficial depending on their concentrations. 

Moderate levels of calcium and magnesium can be beneficial 

because they are plant nutrients and are often difficult to formulate 

into liquid fertilizer solutions. Higher concentrations cause deposits, 

or "scale," on irrigation nozzles and other surfaces. Other ions, 

especially those of boron (B), can be toxic to tree crops at 

concentrations of less than 1 ppm. Iron (Fe) is a necessary plant 

nutrient, but high Fe levels in irrigation water can cause unsightly 

staining of plant foliage and other nursery surfaces (fig. 1 .2.2C).

Testing water quality. Many different water quality guidelines 

have been published because different standards apply for each 

purpose. Both the total salinity and the concentration of the 

individual salt ions are important. Ionic concentrations may be 

expressed as milligrams per liter (mg/I) or parts per million (ppm) 

which, for our purposes, are equivalent. The other standard unit is 

milliequivalents per liter (meq/I). (The definition of these units and 

their conversions are provided in section 4.2.4 of volume four of 

this series.) f=or site evaluation purposes, four different factors 

are important:

pH. This index of relative acidity or alkalinity is the most frequently 

discussed water quality factor but, in terms of horticultural 

importance, it is actually overrated. The pH of typical irrigation 

water is usually about neutral (pH 6.5 to 7.5). Most forest and 

conservation seedlings grow well at mildly acidic pH levels of 5.0 to 

6.0, and weak acid solutions can be easily injected into the 

irrigation system to achieve this target level (table 1.2.2). Irrigation 

waters with pH values below 6.0 are rare, but water that exceeds 

pH 7.5 should be further evaluated. These higher pH values are 

often symptomatic of detrimental concentrations of sodium.

31
Figure 1.2.2--Potential sources of irrigation water must be tested. 

Pond water may be contaminated with fungal pathogens (A), and 

groundwater can contain high concentrations of salts, which can 

burn seedling foliage (B). Other water sources may contain 

bicarbonate ions or iron, which can stain plants and containers (C).

evaluations do not include tests for these elements and so special 

testing is warranted if the potential nursery site has a history of 

heavy metal contamination, or if the water comes from an aquifer 

containing metal ores. Water effluent from sewage treatment plants 

can also be contaminated with heavy metal ions. Water can also be 

contaminated by many other compounds including pesticides or 

other hazardous chemicals. Tests for organic chemicals such as 

pesticides are extremely expensive, however, because each 

potential pollutant requires a different testing procedure.

Accessory ions. Although they are not toxic to seedlings, several 

other ions indirectly affect irrigation water quality (table 1.2.2). 

Calcium (Ca 2+), magnesium (Mg2+), sulfate (SO4

2-

), and 

bicarbonate (HCO3

-

) affect other water quality indices such as 

hardness and alkalinity, and HCO3

-

 can also cause foliage spotting. 

Besides being mineral nutrients, Ca2+ and Mg2+ can partially 

counteract the deleterious effects of Na+ and CI- ions.

Other indices. Several other water quality parameters are 

sometimes encountered in the literature:

• Total dissolved solids (TDS), an older measure of total 

salinity, is sometimes called the total dissolved salts. The 

TDS is calculated by merely adding up the concentrations of the 

various dissolved constituents

Electrical conductivity (EC). This index of salinity measures the 

total concentration of dissolved ions by passing a weak electrical 

current through the solution. An EC meter reads the electrical 

conductivity in microsiemens per centimeter (μS/cm), which is 

equivalent to micromhos per centimeter (μmho/cm); the higher the 

reading, the higher the salt concentration in the solution. Irrigation 

water with an EC reading of more than 1,500 μS/cm is considered 

to be too saline for successful container nursery production (table 

1 .2.2).

Toxic ions and heavy metals. Three salt ions that are commonly 

found in irrigation water can actually be directly toxic to seedlings at 

high concentrations: sodium (Na+), chloride (CI-), and boron (B) 

(table 1.2.2). Contamination of irrigation water with elements (known 

as heavy metals) such as lead, chromium, cadmium, and mercury 

can also be a problem because even low concentrations can be 

toxic to plants (U.S. Environmental Protection Agency 1982). 

Standard water quality

32
These values assume a porous and free-draining growing medium. Water with much lower salt concentrations can cause serious problems if poor

drainage or irrigation practices allow salts to accumulate. Water pH limits are relatively easy to adjust with 

acid injection (see explanation in text).

4: 1 part per million (ppm) = 1 milligram per liter (mg/I); the conversion between milliequivalents (meq) and ppm varies with the atomic weight and

electrical charge of the ion. Boron has several different ionic forms in irrigation water and therefore a specific conversion cannot be made.

Source: From various sources, see table 4.2.7 in volume four of this series.

(Hem 1992) and is reported in parts per million (ppm). An 

approximate EC reading in microsiemens per centimeter 

(μS/cm) can be obtained by dividing TDS by 0.64.

• Total alkalinity, another traditional water quality index, is 

defined as the capacity to neutralize acid. In natural water, 

alkalinity is practically all produced by carbonate and 

bicarbonate ions, and so most water tests report alkalinity as 

the sum of these two ions (Hem 1992). Alkalinity is closely 

related to pH and so the higher the reading the more acid will 

be required to lower the pH to target levels. When irrigation 

water has a total alkalinity rating of greater than 100 ppm, it 

becomes operationally difficult to lower the pH to the ideal 

range for plant growth (Tayama 1991).

• Hardness is a traditional water-quality term referring to the 

precipitate ("scum") formed by reaction of soap with calcium 

and magnesium ions in the water. Most water analyses 

compute "total hardness as calcium carbonate (CaC03)" by 

combining the concentrations

of these two ions (Hem 1992). Although useful for determining 

water quality for domestic (cleaning ability) or industrial 

purposes (scale deposits), the relative terms "hard" and "soft" 

have no practical use for determining irrigation water quality. 

However, water for nursery use should never be "softened," 

for this process replaces calcium and magnesium ions with 

those of sodium. Domestic water that has been softened often 

contains levels of sodium ions high enough to cause injury to 

container nursery crops.

On-site observations. Although a complete water-quality analysis is 

always necessary, some basic observations will give the nursery 

developer some important clues to irrigation water quality. Water 

containing high levels of salts often tastes heavy and flat; if it tastes 

salty, chloride is probably greater than 250 ppm (U.S. 

Environmental Protection Agency 1982). Whitish crusts or scale 

deposits on faucets indicate high concentrations of calcium and 

magnesium bicarbonates in the water

33
supply. Note the effort and amount of soap required to work up a 

lather; if little soap or effort is required and the soap is difficult to 

rinse off, the water is relatively "soft" and the water contains a high 

concentration of sodium compared to calcium or magnesium. 

Brown or orange-brown staining indicates high iron concentrations. 

Although this problem is not critical to plant growth, water that is 

high in iron will eventually stain containers and other greenhouse 

surfaces (fig. 1.2.2C). A sulfur or "rotten egg" taste or smell 

indicates the presence of sulfides, which are toxic in high 

concentrations.

Collecting and analyzing water test samples. If the site looks 

promising, a sample of the irrigation water should be collected (fig. 

1.2.3). Be aware that the quality of different water sources at a 

potential nursery site can vary significantly. Surface water may be 

radically different from well water, and quality can even change 

from one irrigation well to another. The quality of river or stream 

water changes with the season and so water samples should be 

collected several times during the year. The quality of an irrigation 

water source is a composite of a wide variety of factors, and so a 

complete water analysis should be performed (table 1.2.2). In 

addition to the principal water quality indices and the 

concentrations of the toxic ions, the concentrations of other 

accessory ions (specifically calcium, magnesium, and bicarbonate) 

also should be determined. (Water sampling procedures and a 

complete discussion of irrigation water analysis are provided in 

volume four of this series.)

In summary, the water analysis should contain the 

following information:

• Electrical conductivity--Estimates the total salt content, 

and serves as a starting point for tracking changes in water 

quality on a regular basis.

• Specific ions--Measures the concentration of the three directly 

toxic ions (sodium, chloride, and boron), and well as the other 

accessory ions that can indirectly water quality (table 1.2.2). 

Other heavy metals should be tested for if a problem is 

suspected.

• pH-Nice to know but rarely a problem that cannot be corrected.

Be concerned and make further tests if the pH is over 7.5.

• Acid titration curve--Gives quantitative information about the 

amount of acid to add to the irrigation water to reduce the pH to 

specific levels. When doing the titration, be sure to use the 

same acid that will be used operationally because different 

acids vary in their ability to neutralize alkalinity.

Estimating amount of water use. Once the quality of the irrigation 

source is verified, both the total amount of water per season and 

the rate at which the water can be supplied must be evaluated. 

Estimates of total annual water use will be needed from potential 

nursery developers when applying for water rights, and the peak 

water use rate must be estimated to determine the required 

irrigation pump capacity and to assess the need for water storage 

ponds or tanks.

Total water demand. During the site evaluation process, nursery 

developers should calculate the total amount of irrigation water 

that will be required per season or year. In addition to current 

water requirements, projected nursery expansion must also be 

considered when estimating total annual water demand. If the 

primary water source is unreliable, it may be wise to evaluate a 

potential backup source of irrigation water; for example, water 

availability can be a problem in nurseries with open growing 

compounds that need to irrigate for frost protection during cold 

weather (Appleton 1986). Nurseries that rely on surface water 

sources that freeze may want to dig a well for a backup source of

irrigation water.

Figure 1.2.3-The first step in determining the suitability of a 

potential nursery site is to collect water samples from all potential 

sources of irrigation water and obtain a complete water analysis.

34
The total amount of water that a container tree nursery will require 

depends on many factors, including climate, type of nursery and 

irrigation system, container volume, and the water use patterns of 

the crop. Total water demand has been given in many different 

units, but volume of water that must be supplied over some time 

interval per unit area of growing space or per thousand seedlings is 

most useful for planning purposes (table 1.2.3).

Water will also be required for purposes other than crop production, 

such as cooling, landscape, and domestic uses, and estimates of 

these requirements can be developed with normal engineering 

calculations. Tinus and McDonald (1979) estimated that a nursery 

consisting of a 464-m2 (5,000-ft2) greenhouse and a 695-ml 

(7,500-ft2) shadehouse would require approximately 3,800,000 I/yr 

(1,000,000 gal/yr) for other nursery and domestic uses.

Rate of water demand. During the site evaluation process, an 

estimate of the peak water use rate is needed to determine 

irrigation pump output. For example, if peak water use exceeds the 

maximum supply rate from a well, then water storage ponds or 

tanks may be needed (fig. 1.2.4). Peak water use information will 

also be needed during nursery development to determine the size 

of the irrigation pumps and supply pipes and the overall design of 

the irrigation system (Aldrich and Bartok 1989).

The peak use rate will vary significantly with different types of 

irrigation systems (sprinklers versus drip) and with irrigation system 

design. Although fixed sprinkler irrigation is the most common 

design in container tree nurseries at present, movable boom 

irrigation is becoming more popular and requires a much lower 

peak water use rate. The increasing concern about surface 

discharge and potential groundwater pollution will undoubtedly 

require increased irrigation efficiency with a corresponding 

decrease in the rate of water demand.

35
Peak water use rates should be expressed as volume of water per 

unit time per unit area of growing space. The total water use rate 

estimate for the proposed nursery facility need not assume that the 

whole irrigation system will be on at the same time, but estimates 

must reflect which critical uses will be used simultaneously under 

the most extreme conditions. For example, if extremely hot 

weather dries out growing media so fast that the entire nursery 

growing area must be irrigated every 4 hours to prevent severe 

moisture stress, then the water flow rate with all the sprinklers on 

is the peak use rate. Future nursery expansion should also be 

considered when estimating peak use rates.

The traditional way to estimate peak water use rates for sprinkler 

irrigation systems is to calculate the depth of water in centimeters 

(or inches) that need to be applied to the growing area during the 

irrigation interval, and then convert those depth units to the rate 

units of volume per time, that is, liters per minute (or gallons per 

minute) (Pair and others 1983). For example, container tree 

nurseries can require water at rates ranging from 16 to 20 I/h/m2

(0.4 to 0.5 gal/h/ft2) of growing area using containers that are 20 cm 

(8 inches) deep. However, if larger containers are planned, then 

more water will have to be applied within the same irrigation interval 

and these higher output nozzles will cause a proportionate increase 

in the peak water use rate. So, if 30-cm-deep (12-inch-deep) 

containers are used, then the peak water use rate would increase to 

30 I/h/m2 (0.75 gal/h/ft2) of production area (Tinus and McDonald 

1979) .

36

Peak rates must consider all types of water use that may be used 

at the same time: production, cooling, landscape, and domestic. 

Assuming a 20 I/h/m2 (0.5 gal/h/ft2) application rate for a 464-m2

(5,000-ftZ) greenhouse, the peak water use rate would be 11,800 

I/h (3,125 gal/h), or about 200 I/min (52 gal/min) (Tinus and 

McDonald 1979). The authors calculated other nursery uses at 150 

I/min (40 gal/min). Therefore, after adding the production and other 

water use rates and rounding up, the total water rate requirement 

would be around 378 I/min (100 gal/min).

1.2.2.3 Inexpensive and reliable energy source

Container tree nurseries require relatively large amounts of energy, 

although the exact requirements will vary with the climate, the type 

of propagation structures, the sophistication of the environmental 

control equipment, and the type and timing of the crop. Fully 

controlled structures require large amounts of fuel for heating and 

electricity for operating environmental control equipment. Even 

nurseries that grow seedlings in open growing compounds require 

electrical energy to operate irrigation pumps and other equipment. 

Access to relatively large amounts of energy is so important to 

container nursery operation that other site factors may have to be 

compromised so that a location with good access to utilities can be 

selected (Hanan and others 1978). Consequently, the availability 

and reliability, and the amount and cost, of various energy sources 

at a potential nursery site are key factors in site selection.

Availability and reliability. All container nurseries require 

electricity to power the heating and cooling systems and to operate 

other nursery equipment. Although the type of electrical service will 

vary with nursery design, three-phase 240-V service is most 

efficient for large motors and so is preferred if available (Davidson 

and others 1988). To determine the electrical demand, the number 

and size of electrical motors, lights, environmental control 

equipment, and other users of electricity must be estimated. 

Aldrich and Bartok (1989) provide charts giving a rough idea of the 

electrical requirement or contact an electrician for a professional 

estimate. Remember to allow for future expansion. If the proper 

type of service is not available at the potential site, then the cost of 

bringing in a new electrical line must be included in the site 

development cost estimate. The reliability of electrical service 

varies from location to location, and it would be wise to inquire 

about potential
problems from other local businesses. Although all container 

nurseries should have a backup generator in case of short-term 

power failure, chronic problems with reliability of electrical power 

are unacceptable.

Because heating is not necessary in milder climates, electricity is 

the only energy source that is needed. In colder locations, 

however, container nurseries require an additional source of 

energy for heating. Although electricity can be used for heating 

growing structures, it is almost always too expensive compared to 

other energy sources. Most common fuels have been used to heat 

container tree nurseries including natural gas, propane, and fuel 

oil, and so nursery developers should determine the availability and 

cost of these fuels for each potential site. The practicality and cost 

of delivering fuel to the nursery must also be considered; natural 

gas may not be available in some locations, but propane and fuel 

oil can be delivered to almost any site. Some nurseries heat their 

growing structures with alternative energy sources, such as wood, 

used oil, and waste heat (see chapter three in this series for more 

information on fuels).

Quantity required and cost. In order to compare the relative 

costs of different energy sources, an estimate of energy 

requirements of the proposed nursery facility should be made. In 

traditional greenhouses, maintaining temperatures at ideal levels 

for plant propagation is by far the most energy-demanding 

operation. Heating requires the greatest amount of energy in 

temperate zone nurseries, consuming between 70 to 85% of the 

tota l energy budget. Cooling is the second-most energydemanding 

operation, using from 5 to 10% of the total energy demand 

(Roberts and others 1989).

The amount of energy required to keep a growing structure at 

optimum temperatures is a function of the type of heating system 

and the rate of heat loss. Heat loss calculations consider factors 

such as greenhouse area, type of structure and covering, and 

surrounding climate. Sample calculations can be found in general 

greenhouse publications, including Aldrich and Bartok (1989) and 

Roberts and others (1989). Cameron (1982) presents a detailed 

analysis of energy requirements for producing a winter crop of tree 

seedlings in the Maritime Provinces of Canada.

Solar and alternative energy sources. The potential use of 

energy sources other than fossil fuels should always be considered 

during container nursery site selection. Greenhouses are designed 

to capture solar energy, and so the orientation of the growing 

structure is of paramount importance (see section 1.2.2.1). The 

possibility of using solar energy as a sole source of heat has been 

thoroughly analyzed (Midwest Plan Service 1983), but even the 

most sophisticated solar greenhouse designs will require a 

supplementary source of energy. Although limited to certain sites, 

geothermal energy is another potential source of energy for 

heating greenhouses (White and Williams 1975), but this option can 

be quite expensive unless circumstances are very favorable 

(McDonald and others 1976). By locating next to a power plant or 

major industry, greenhouses can make use of the waste heat that 

is a byproduct of energygenerating processes (White 1976). 

Although these alternative energy sources should be considered 

wherever the opportunity exists, traditional fuels will continue to be 

the major source of energy at most locations.

1.2.2.4 Adequate land area

The amount of land selected for a container tree nursery must be 

large enough for the production areas and support buildings, and 

also-allow for efficient movement of equipment and materials. The 

shape of the parcel may be more important than the actual area 

because greenhouse ranges tend to be elongated facilities. In 

addition to immediate needs, the nursery developer should 

evaluate potential nursery sites on the basis of their space for 

possible expansion. In fact, Nelson (1991) recommends looking for 

a site that has at least twice the planned growing area. Sketching 

potential expansion areas on the existing site plans along with 

access roads and support buildings is strongly recommended. It is 

much easier to sell surplus land at some future date than to 

acquire some much-needed space for expansion or try to operate 

at two separated locations. Many nurseries have been developed 

in rural locations, only to find themselves surrounded by urban 

development a few years later (fig. 1.2.5).

37
1.2.2.5 Ecopolitical concerns

This site selection factor was not even considered a few years ago, 

but it has since become one of the most critical evaluation criteria. 

Restrictive land-use laws and concerns about pesticide use and 

potential soil and groundwater contamination have severely 

reduced the number of sites suitable for nursery development.

Land-use zoning and building restrictions. Many areas, 

especially those around municipalities, have zoning laws that affect 

development, and some even prohibit certain types of businesses. 

In general, container nurseries are considered agricultural 

businesses and can be constructed wherever agriculture is 

permitted, but potential developers should always discuss their 

plans with local authorities just to be certain. Nursery type is also an 

important consideration, as some local governments restrict the type 

of propagation structure that can be constructed on a site. 

Developers should attempt to predict future zoning changes by 

studying development patterns for the surrounding region (Nelson 

1991). It is also a good idea to talk to your potential neighbors 

because existing landowners are becoming more involved in local 

zoning issues. This is not just a problem in urban areas, as many 

former city dwellers are moving to the country and often object to 

any type of new development. This can even occur in areas that are 

already zoned for agriculture and greenhouses (Roberts 1992).

38

Most zoning commissions require that potential nursery developers 

submit a detailed development plan and map, and a public hearing 

is often necessary. Be aware that all this may take considerable 

time. It can take from 3 months to 3 years to get through all the 

bureaucratic hurdles and obtain the necessary building permits 

(Roberts 1991). And, even if you can get the necessary permits, 

the cost may be restrictive, especially for container nurseries with 

many small propagation structures. Although generally classified as 

temporary structures, some municipalities tax plastic-covered 

greenhouses as permanent structures (Boodley 1981). A complete 

discussion of zoning ordinances and how they may affect container 

nursery development and operation is given in Bartok and Aldrich 

(1989).

In addition to providing information on building codes and zoning 

restrictions, the city or county clerk can provide valuable advice 

on other permits, tax laws, and business licenses that could affect 

the practicality of developing a container nursery on a particular 

land parcel (Davidson and others 1988). One city in California 

has just recently been assessing a new traffic-impact tax that 

adds $21.50 per mz ($2 per ftz) to the cost of constructing any 

new building (Roberts 1991). Some local governments encourage 

nurseries by classifying them as agricultural businesses, which 

can be some protection against the prohibitive tax increases that 

can result from future rezoning.

Potential chemical pollution. The fate of agricultural chemicals 

and the possible pollution of soil or water must be considered 

during nursery site selection. The principal agricultural pollutants 

that are associated with container tree nursery operations are 

pesticides (and their degradates), nitrates, and phosphates. 

Pesticides and nitrates can adversely affect human health, and 

nitrates and phosphates pose a significant threat to general water 

quality through eutrophication. Because container nurseries 

typically apply most of their pesticides and fertilizer through the 

irrigation system, the surplus water either runs off the growing area 

or soaks into the ground (fig. 1.2.6A). Irrigation water that runs off 

the site legally becomes a discharge, which is becoming 

regulated in many areas of the country (Landis and others 1992). 

For example, concerns about agricultural pollution in western 

Oregon resulted in the development of the "Container Nursery 

Irrigation Water Management Plan," which gives nurseries two 

options: eliminate all irrigation runoff discharges or obtain runoff 

discharge permits (Grey 1991).
Developers should conduct an environmental audit of a candidate 

nursery site to determine baseline levels of potential pollutants and 

determine the potential for future problems (Aylsworth 1993). 

Nurseries that are constructed on already contaminated soil could 

be liable for any resultant pollution, and many banks are requiring 

environmental audits before approving loans to buy new property. 

Talk to local environmental protection and agriculture agencies and, 

if there is concern, it may be wise to hire a professional consultant 

to do soil and water testing (Kammel 1991). There are new 

techniques for managing agricultural pollution. Some progressive 

nurseries are constructing on-site water treatment facilities 

including recirculation ponds (Skimina 1992) and constructed 

wetlands (Dumroese and others 1992) (fig. 1.2.613). Constructed 

wetlands and other water treatment facilities require a fair amount 

of land area, which must be considered during initial site selection, 

and their construction costs must also be included in site 

development plans.

39
1.2.3 Secondary Site Selection Criteria

Although not as important as the criteria discussed in the previous 

section, the following factors should be considered during site 

evaluation. They can greatly increase the efficiency of a nursery 

operation and reduce operating costs.

1.2.3.1 Protected microclimate

In addition to having unobstructed solar aspect, a potential nursery 

site should be located in a protected area with the most equitable 

climate in the local region (fig. 1.2.7A). Within any geographic 

area, nurseries should be located in areas that are not subject to 

extremes in temperature or damaging winds (Davidson and others 

1988). On the other hand, a moderate degree of air movement is 

necessary for ventilation during warm weather (Hahn 1982). As 

long as they do not shade the growing area, trees on the windward 

edge of the nursery site can act as a natural windbreak and protect 

against damaging winds or snow accumulation (fig. 1.2.713). 

However, trees or other obstructions on the lower edge of the site 

can serve as barriers to cold air drainage, and valley bottoms or 

other low sites that collect cold air should be avoided (Nelson 

1991).

Obviously, potential nursery sites near industries or utilities that 

could generate possible pollutants should never be considered. 

Air pollution is an increasingly serious problem in industrial or 

urban areas, and so nurseries should never be located in 

confined locations where photochemical smog may accumulate 

Chic to poor air circulation (Davidson and others 1988).

1.2.3.2 Gentle topography

The general topography of a potential nursery site i> important 

for both biological and economical reason A relatively level site 

reduces the cost of land leveling. during construction and 

increases the ease of moving equipment, supplies, and vehicles 

after the site is developed (Nelson 1991). South-facing slopes 

(in the northern hemisphere) are preferred because the higher 

solar input will lower heating costs (fig. 1.2.7A); this becomes 

more critical in areas where energy costs are high (Boodley 

1981). Modern nurseries should be designed so that irrigation 

runoff can be collected and recycled, thus making a slightly 

sloping topography desirable.

40
1.2.3.3 Seasonal labor supply

The success of a container tree nursery depends on the quality of 

the available work force (Boodley 1981). In addition to a small 

permanent professional staff, a container tree nursery requires a 

reliable source of semiskilled labor for several peak work periods 

during the year, when tasks such as sowing or grading must be 

completed in a short time (fig. 1.2.8). During the site evaluation 

process, it is a good idea to contact the local employment agency 

and other agricultural businesses in the vicinity to learn about 

available labor sources and skill levels. You should also inquire 

about other seasonal labor demands in the area and compare the 

temporal patterns to your own needs. The existence of other 

employers of part-time workers can be an advantage if the other 

business is able to use workers at times when the nursery labor 

demand is low. Because of perennial problems with locating 

workers, however, some nurseries are experimenting with 

contracting most labor-intensive tasks (Davidson and others 1988)

The number of employees required depends on the size and 

complexity of the operation. An average of one laborer for each 

200,000 seedlings, and at least one technical supervisor for each 

3,000,000 seedlings may be used as a rule of thumb. Nurseries 

should also considering hiring one additional person as a backup 

supervisor.

1.2.3.4 Accessibility

A good nursery site must be accessible for regular delivery of nursery 

supplies and shipping of nursery stock. Most supplies and the vast 

majority of container nursery stock are delivered by truck, making good 

all-weather roads and accessibility to regular shipping routes and 

highways important. Access roads should not have any steep slopes or 

sharp turns that would prohibit safe operation of large delivery trucks. 

Weight limitations may be a restriction in some parts of the country and 

so check with the local highway department (Davidson and others 

1988). Essential supply and maintenance services should be available

nearby. Remote locations may increase the cost of supplies, 

particularly in locations where fuel oil or propane must be delivered 

regularly (Nelson 1991).

A good nursery location will require an all-weather surfaced road 

system for handling supplies and seedling deliveries (fig. 1.2.9A). For 

forest and conservation projects, the "planting window" is determined 

by the availability of soil moisture or when the outplanting site becomes 

free of frost, and so seedlings often must be harvested and processed 

during rainy or snowy weather (fig. 1.2.913). For nurseries with 

customers in mountainous terrain, the delivery season can go on for 

many months; for example, container nurseries in the Pacific 

Northwest begin shipping seedlings to low-elevation coastal planting 

sites in February and often continue deliveries until high-elevation sites 

become free of snow in May or June. Therefore, a good container 

nursery site must have good year-round accessibility.

Nurseries must also be easily accessible to workers, especially the key 

personnel who respond to emergencies. Regardless of how well a 

nursery is designed for reliable operation, there will be times when key 

nursery workers must be able to respond within a hour or less. If 

accessibility is a potential problem, then it may be necessary to provide 

a dwelling on the site, and this cost must be considered during site 

evaluation.

41
1.2.3.5 Distance to markets

The distance from the potential nursery site to the delivery point 

must also be considered during the site evaluation process. The 

prospective nursery developer should contact potential nursery 

customers and inquire about their delivery needs or desires. In 

some situations, customers will pick up their seedlings at the 

nursery but often customers expect the nursery to deliver the stock 

to intermediate storage or to the outplanting site. Most large 

government agencies or forest companies have their own 

refrigerated delivery vans and seedling storage facilities, but 

smaller customers will probably require delivery direct to their 

outplanting location. A few container nurseries deliver most of their 

seedlings by overnight mail or parcel delivery. In this case, the 

pickup costs and reliability of the various parcel carriers must be 

evaluated.

Seedling delivery can present an interesting dilemma when trying 

to locate a forest nursery: whether to locate a container facility in a 

mild climate where the cost of heating and other services will be 

less or whether to select a more remote location where delivery 

costs will be minimal. Traditionally, nurseries were located close 

to outplanting sites to minimize shipping distances, but with 

modern refrigerated storage and delivery vehicles, this is no 

longer necessary. Of course, the cost of delivery increases with 

distance as does the potential for problems, and so all aspects of 

the situation should be carefully evaluated (see section 1.1.4.3 for 

more discussion).

42
1.2.4 Evaluation of Alternative Sites

All the different site selection factors at a variety of potential 

nursery locations need to be considered analytically. Sometimes 

one or two factors are so important that the choice is obvious, but 

more typically, each site has both good and bad points, and so the 

decision becomes more difficult. In these situations, the various 

sites and site selection criteria should be arrayed in a decision 

matrix, produced in the Kepner-Tregoe decisionmaking process 

(Kepner and Tregoe 1965).

The decision matrix (table 1.2.4) is constructed by listing the 

potential nursery sites across the top and the significant site 

selection criteria down the left side. The next step is to assign each 

site selection criterion an importance value or weight on a scale 

from 1 to 10, with the most critical factors receiving the highest 

scores and the

less important ones progressively lower scores. Next, the suitability of 

each potential nursery location is evaluated and rated, again on a scale of 

1 to 10, based on the information that has been gathered. Once that is 

accomplished, the score for each cell in the matrix is calculated by 

multiplying the weights for each site selection factor by the rating for each 

site. Finally, the weighted scores are totaled for each site and, if the 

weights and rankings have been objectively assigned, then the potential 

nursery site with the highest total ranking should be the best. If all of them 

are close in score, then the process should be repeated, and careful 

attention paid to the relative weights and the ratings of the factors. If the 

scores are still close, the sites are probably equally good.

43
1.2.5 Summary

The selection of a suitable site for a container tree nursery is a 

formidable challenge. A successful container nursery must be 

carefully matched to the environmental conditions on the site and 

so developers must carefully analyze climatic records. A potential 

container nursery site consists of critical factors and desirable 

factors. Critical site selection criteria, especially unobstructed solar 

access and good water quality, are essential to a successful 

nursery operation. Desirable attributes include those site selection 

criteria that are not absolutely necessary but will increase the 

economy and efficiency of the nursery operation. The amount of 

land selected for a container tree nursery must be large enough for 

the production areas and support buildings and also allow for 

efficient movement of equipment and materials. In addition to 

immediate needs, the nursery developer should evaluate potential 

nursery sites on the basis of available space for possible 

expansion. Ecopolitical site selection factors, notably land-use 

zoning and concerns about pesticide use and potential 

groundwater contamination, have severely reduced the number of 

sites suitable for nursery development. Once a list of potential 

nursery sites has been identified, they need be compared 

analytically. Sometimes one or two factors are so important that the 

choice is obvious, but more typically, each site has both good and 

bad points. Using a decision matrix approach will help the nursery 

developer analyze the various sites and reach an objective 

decision.

44
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46