81

The Container Tree 

Nursery Manual

Volume Seven

Chapter 3

Harvesting
82
83

Container nursery managers wait anxiously until they can

begin to harvest their crop because, once plants are graded

and placed into storage, the amount of risk decreases dramatically. Scheduling the best time to harvest is critical

because plants need to be at their peak of quality yet

hardy enough to withstand the sequential stresses of packing, storage, shipping, and outplanting.

“Lifting” is an historical term adopted from bareroot nursery harvesting when seedlings are physically removed

from the soil, and is still used in container nurseries as an

operational synonym for harvesting. “Lift and pack” is

another bareroot nursery term that has been adopted by

container growers when referring to the harvest operation.

When scheduling plant harvest, the first and most important consideration is whether the stock will be lifted and

outplanted immediately (“hot-planted”), or harvested when

dormant and then stored for later shipment and outplanting. 

Methods of harvesting container stock across North

America are a function of nursery size and location, plant

species, research input, and tradition. Many large nurseries in the western US and Canada remove plants from

containers and package them (“lift and pack” or “pull and

wrap”). They use refrigerated storage to handle large

orders that must all be processed simultaneously. This is

the case in much of the Pacific Northwest where winter

temperatures are variable and snow is absent or intermittent (for example, Kooistra 2004). In eastern Canada,

however, temperatures remain cold enough that container

stock can be stored outdoors or some nurseries use snow

making equipment to supplement the snowpack (White

2004). The harvest and storage of other native plants is

considerably different than for commercial conifers.

Because of the sheer number of species, the wide variety

of container sizes, and the fact that little or no research

has been done on dormancy or hardiness, native plants

may require special harvest and storage procedures (Burr

2005).

7.3.1.1 Hot-planting

Hot-planting is done during summer or fall when plants

are not completely dormant or hardy, and so plants must

be handled with care throughout the process. This means

that stock is lifted, held for a short time with or without

refrigerated storage, and outplanted within a week or two.

Timing is the key to a successful hot-planting program,

and it is critical to minimize the time from when stock is

harvested to when it is outplanted. This tight timeline and

the fact that the stock is not fully hardy mean that most

hot-plantings must be relatively close to the nursery.

Greenhouse stock that will be hot-lifted is usually held for

several weeks in a shadehouse or open compound to

develop some degree of hardiness before outplanting.

Some nurseries use moisture stress or blackout to hasten

the hardening process. When the customer notifies the

nursery that the outplanting sites are ready, the stock is

graded to specifications and a final “shippable” inventory

is calculated. Plants should be packed standing up in

boxes to encourage air exchange, and allow for possible

irrigation on the outplanting site. Don’t pack in plastic liners which restrict air flow and can trap the heat generated

by plant respiration. Packed stock should immediately be

placed in cooler storage at approximately 4.4 °C (40 °F)

(Frederickson 2003).

For larger planting projects, stock is held for a short period in refrigerated shipping vans at the nur-sery until the

entire order can be shipped. With southern pines,

seedlings harvested for summer hot-planting are generally

stored at 4 to 21 °C (40 to 70 °F) for a week or less

(Dumroese and Barnett 2004).

7.3.1.2 Dormant stock

Most container nursery stock is harvested during the winter dormant season and stored until it can be shipped for

outplanting. Storage methods are discussed in Chapter

7.4. As far as harvesting goes, the key consideration is

whether plants will be placed in open, sheltered, or

refrigerated storage. The type of storage dictates not only

the time of harvest but also the type of packaging. In

open compounds and sheltered storage, plants remain in

their containers whereas, for refrigerated storage, they are

typically removed from their containers, graded, and

packed in cardboard boxes.

7.3.1 Introduction
84

Nursery managers must harvest their crop at its peak of

quality and know how to maintain that quality until

plants are delivered to the customer. This means harvesting

when plants are fully dormant and resistant to the stresses

of harvesting, storage, shipping, and outplanting. This time

period is known as the “lifting window” or “harvesting window”.

Foresters and other nursery customers have observed that

stock harvested during winter dormancy survive and grow

better than plants lifted a few months earlier or later.

Numerous in-house studies and research trials have confirmed these observations. Although most of this research

was done with bareroot stock, the same principles apply

to container stock. Whereas harvesting bareroot plants at

their peak dormancy is usually restricted or compromised

by too muddy or frozen soils, container plants can be harvested throughout the winter dormant season. Given this

potentially wide harvest season for container stock, let’s

discuss some ways that growers determine the proper lifting window.

7.3.2.1 Calendar and visual clues

These are the most traditional techniques, and when

based on the combined experience of the nursery staff,

can be quite effective. The procedure is simple—if it takes

4 weeks to harvest the crop, then that amount of time is

subtracted from when the crop becomes fully dormant or

is scheduled to be shipped for outplanting. One calendar

technique for deciding when to harvest is known as the

“F-date”, which is based on the average date of the first

fall frost. Harvesting can begin 30 to 45 days after this

date (Mathers 2004). 

Experienced growers also use several morphological indicators to help them confirm when plants are becoming

dormant and hardy and ready to harvest:

Foliage characteristics. Determining when deciduous

species are ready to lift is relatively easy, because their

leaves change color and eventually fall off. Even evergreen species can show foliar signs when they are

becoming dormant. For example, the cuticle of leaves or

needles becomes thicker and waxier so that the plant can

tolerate desiccation during the winter. Experienced growers can feel a difference in foliage texture and rigidity

Figure 7.3.1—Plants develop visible signs of dormancy

and hardiness such as bluish wax deposits on their foliage

(A). Bud size and development is also a sign of dormancy

and plant quality; large buds containing many leaf primordia (B) are superior to smaller, less developed buds (C).

Photos B&C by Steve Colombo).

7.3.2 Scheduling the Winter Harvesting Window

A

B C
85

when plants become hardy, and the needles of some

species exhibit a slight change in color. For example, the

actively growing foliage of Engelmann spruce (Picea

engelmanii) is bright green whereas dormant foliage

becomes bluer in color because of the waxy cuticle that

develops on the surface (Figure 7.3.1A).

Buds (presence, size, and number of primordia). Plants

with determinate growth patterns, such as pines and

spruces, form a bud at the end of the growing season. In

the temperate zone, most people look for large buds with

firm scales as an indication of shoot dormancy and plant

quality. Other plants, such as junipers and cedars, have

indeterminant growth and a terminal bud is not formed.

Some semitropical pines, such as longleaf (Pinus palustris)

in the southern United States, also do not form buds in

the nursery (Jackson and others 2007). (See section 6.1 in

this series for more information on determinate and indeterminate growth patterns).

Bud size and length has traditionally been used as a good

indicator of when plants are ready to harvest. In eastern

Canada, counting the number of bud primordia is one

way that nurseries determine the timing of their harvests

(Figure 7.3.1 B&C). KBM, a private seedling testing laboratory in Thunder Bay, Ontario, offers bud dissection on a

fee basis (Colombo and others 2001). 

Presence of white root tips. Some growers consider the

presence or absence or white root tips as a sign of plant

dormancy. Roots never go truly dormant, however, and

will grow whenever temperatures are favorable. Therefore, the presence of white root tips has little value in predicting dormancy or hardiness, but numerous long, white

roots indicates that plants have been exposed to temperatures above 10 °C (50 °F)—see Figure 7.2.41C in Chapter

7.2.

So, although it is not too scientific, scheduling the lifting

window by the calendar and visual clues can be effective

if based on actual nursery and field experience with specific plant species. 

7.3.2.2 Outplanting trials

Another traditional method of determining when it is safe

to lift nursery stock involves outplanting performance. Over

Figure 7.3.2—An effective, but time consuming, way to

establish lifting windows is to lift plants throughout the

harvest season and monitor their performance after outplanting. These results show that the lifting window for all

four conifers was from late November to the end of

February. Because they became dormant sooner, high elevation species such as Shasta red fir (Abies magnifica)

had a wider window than species from lower elevations

(modified from Jenkinson and others 1993).

a period of years, nurseries can determine their lifting windows from observations on plant survival and growth after

outplanting. This technique has been used for bareroot

stock but few results have been published for container

stock. In a comprehensive study of four bareroot conifer

seedlings from northern California, samples were collected

at monthly intervals throughout the winter and then outplanted and evaluated for first-year survival (Jenkinson and

others 1993). The resulting data shows that lifting windows

can vary significantly between species and between seedlots within a species (Figure 7.3.2). Outplanting trials are

effective in establishing lifting windows but the drawback is

that it takes from 5 to 10 years to accumulate enough data

to account for seasonal weather variation. In addition, separate trials would be needed for customers from different

climatic regions. 
86

7.3.2.3 Plant quality tests

Plant quality testing is discussed in detail in Chapter 7.2,

and several tests have been used to determine when container stock is ready to harvest. 

Root growth potential (RGP) is the most widely-known

quality test and many experiments have attempted to correlate RGP with lifting windows. While this test provides

an indication of vitality and relative vigor, RGP readings

typically vary too much from year to year to be useful. 

Estimating bud dormancy with chilling sums. All growers

know that plants should be harvested when they are dormant. Unfortunately, growers lack a quick-and-easy test to

determine dormancy status—current tests only measure

bud dormancy. Therefore, the easiest and most practical

method for estimating intensity of bud dormancy is based

on the chilling requirement. The concept is logical

enough—the cumulative exposure of plants to cold temperatures controls the release of dormancy. Therefore, by

measuring the duration of this exposure, it is possible to

estimate the intensity of dormancy indirectly. 

The operational application is known as chilling sums, or

degree-hardening days. The process involves measuring

the temperature throughout the day and calculating the

duration of time below some reference temperature—this

is known as the chilling sum. This chilling sum can be

calculated with several different formulas and environmental monitoring equipment is available that will calculate chilling sums automatically (see 7.2.5.1 for more

details).

Cold hardiness testing. It’s traditional knowledge that

plants should be hardy enough to withstand the stresses

of harvesting, storage, shipping, and outplanting. There

are many types of hardiness but cold hardiness has

proven to be easiest to measure and the best predictor of

when to lift container stock. For more than 20 years, cold

hardiness tests have been used to determine lifting windows and estimate storability in Canadian container nurseries. Their critical threshold is when plants exposed to

cold temperatures show less than 25% visible cold injury

to the foliage (Burdett and Simpson 1984). For open storage, plants must be able to tolerate two consecutive frost

hardiness tests at -15 °C (5 °F)(Colombo and others 2001;

White 2004), whereas for long-term freezer storage, two

hardiness tests at -15 °C (5 °F) or one at -40 °C (-40 °F)

are considered adequate (Colombo and Gellert 2002).

The critical temperature threshold varies for other species.

For example, coastal Douglas-fir in Oregon, 10 or 50 percent cold injury to buds or stem cambium at -15 °C (5 °F)

is more appropriate.

Growth chamber measurements of cold hardiness of

Douglas-fir and ponderosa pine container seedlings were

modeled against weather data to establish lifting windows

(Tinus 1996). Freeze-induced electrolyte leakage tests

demonstrated the year-to-year variation in lifting windows

that can be expected. Comparing the four years modeled,

the starting and ending dates and the duration of the lifting window were significantly different (Figure 7.3.3). 
87

Figure 7.3.3—Cold hardiness, measured as the 50 percent

index of injury from freeze-induced electrolyte leakage

tests, was used to model the lifting window for two southwestern conifers over four winters from 1992 to 1996

(modified from Tinus 1996).

Storage molds are a serious concern during overwinter storage, especially from the fungus Botrytis cinerea that is commonly found on lower senescent foliage (Figure 7.3.4A).

Therefore, just prior to packing plants for refrigerated storage, some nurseries treat their stock with foliar fungicides.

Unfortunately, both nursery workers and tree planters

have complained about skin rashes and other allergic

symptoms after handling fungicide-treated stock. The only

comprehensive study of fungicide effectiveness and pesticide residue was conducted at container nurseries in

British Columbia (Trotter and others 1992). Two fungicides, benomyl (Benlate 50WP) and captan (Captan

50WP), were sprayed on conifer seedlings prior to refrigerated storage using an irrigation boom. In one treatment,

both pesticides were applied through a backpack sprayer.

They found both fungicides were effective when applied

to species predisposed to Botrytis mold. Seedling samples

were collected before and after the standard storage period

to determine pesticide residue levels. Captan was found to

be more persistent than benomyl and levels were signifi7.3.3 Pre-storage Fungicide Treatments

cantly higher when a backpack sprayer was used (Figure

7.3.4B). This short residual effect means that the fungicide

is only effective immediately after application and that

highly susceptible seedlots may still be infected if predisposing conditions exist during or after storage (Trotter and

others 1992). 

Therefore, the decision on whether or not to apply protective fungicides to control storage molds should be considered from both cultural and safety standpoints. Species

and seedlots that are already infected prior to harvest may

benefit from protective fungicides, but heavily-infested or

stressed lots may still develop mold problems during or

after storage. (See Volume 5, section 5.1.6.2 for more discussion of molds and other storage problems).

Figure 7.3.4—Plants grown at high densities often develop Botrytis mold on the lower senescent foliage (A);

pesticide residue levels on foliage of stored plants varied

by nursery and by application method. All treatments

were applied in the greenhouse through an irrigation

boom except PICO-B, which was applied with a backpack

sprayer (B - Species codes: PSME = Pseudotsuga menziesii, PICO = Pinus contorta, PIGL = Picea glauca, PIGL-X

= Picea glauca x engelmannii, TSHE = Tsuga

heterophylla; B modified from Trotter and others 1992).

A

B
88

Container stock is generally processed differently depending on how the crops will be sold and shipped.

7.3.4.1 Small Speculation Orders

Some nurseries, such as state government and private

nurseries, service many, perhaps thousands, of customers

that order a few plants of many different species. Plants to

satisfy these orders are usually grown on speculation and

orders are accepted throughout the winter and spring

shipping season. To facilitate filling and processing orders,

plants are usually harvested, graded, packaged into discrete quantities (for example, 5 or 25; usually the minimum number that can be ordered), and then stored in

bulk bins in a cooler. As orders come in, workers pull

plants from the bulk bins and combine the various

species for shipping, often by mail or parcel service.

7.3.4.2 Large contract orders

Many federal government and forest industry nurseries

grow all or most of their container plants on contract and

so grade, package (often 100 to 500 plants per box), and

store their stock in the same operation by customer.

Depending on the customer preference and the length of

storage, these orders may be held in cooler or freezer storage.

7.3.4 Processing Speculation and Contract Crops
89

Regardless of whether or not container plants are going to

be hot-planted or outplanted as dormant stock, they are

graded for size and appearance according to established

standards or, in the case of contract stock, standards agreed

upon with the customer (see Volume 1, pages 147–149).

“Culls” are plants that do not meet the grading criteria.

Sometimes these criteria are adjusted during the grading

process based on other cull and shipping factors that

become apparent during the process. Typical grading criteria include shoot height, stem diameter at the root collar

(“caliper”), and root plug integrity. In addition, plants are

inspected for physical injury or disease, especially for

Botrytis mold that can spread in storage.

The timing of the grading operation depends on the harvesting methods. To minimize volume and prevent disease during storage, most container nurseries grade their

stock as part of the harvesting process. Some nurseries

that store in open compounds ship ungraded stock to the

outplanting site where they are graded immediately

before outplanting (Dionne 2006).

Container size and the way plants will be packaged and

stored determines the best processing system. For smaller

volume containers, plants can be processed two ways: 1)

grading, storing, and shipping plants in the growth container; or 2) extracting (“pulling” or “lifting”) plants from

the growth container and subsequently grading, packaging, and placing them into storage and/or shipping containers (Landis and McDonald 1981). Because of their

size and weight, larger volume single containers are graded and handled individually. 

7.3.5.1 Storage and shipping in growth container

This process is generally limited to container types with

individual soft plastic “cells” or “tubes” that are held in

hard plastic racks. The most popular containers of this type

are Ray Leach “Cone-tainers”TM and DeepotsTM (Figure

7.3.6A). The harvesting process consists of removing each

container from the rack, grading the plant within it, and

then placing the container into either a “shippable” or

“cull” rack (Figure 7.3.6B). Racks of shippable plants are

stored outside either in shadehouses or under white plastic

sheeting (see section 7.4) until they can be shipped for

outplanting. Cull racks are emptied as time permits.

Because the plastic racks are brittle and can be damaged

Figure 7.3.5—Common grading standards include shoot

height, stem diameter at the root collar (“caliper”), and

root plug integrity.

during handling and shipping (Figure 7.3.6C), some nurseries group shippable containers into bunches secured by

a rubberband or put them in plastic bags (Figure 7.3.6D),

which are then placed in cardboard boxes for refrigerated

storage.

Some nurseries using block containers also leave graded

plants in the growth containers for storage and shipping

to the outplanting site. This is particularly common with

the more durable hard plastic blocks such as the HikoTM

tray, IPL Rigi-PotsTM, and Ropak Multi-PotsTM. In some

nurseries, cull plants are pulled from containers during

the grading process but, in others, no grading occurs and

all plants are shipped to the outplanting site where the

planter makes the final decision regarding plant quality

(Dionne 2006). 

7.3.5.2 Plant extraction

As mentioned earlier, container plants are typically

extracted from their growth container when they will be

7.3.5 Grading and Packaging
90

Figure 7.3.6—Harvesting nursery stock in the growth container is popular for soft plastic cells which can be

removed from their racks (A), graded, and consolidated

into “cull” or “shippable” racks (B). Containers shipped to

the outplanting site must be returned to the nursery

which can result in damage (C), so some nurseries pack

the individual cells into plastic bags (D) and cardboard

boxes.

A B

C

D
91

stored under refrigeration, but often hot-planted stock is

extracted as well. “Pull and wrap” is most common with

large block containers such as the StryoblockTM because

extracting plants reduces the volume of space needed

during storage and shipping. Because harvested, dormant

plants can be stored for up to 6 months, extraction allows

the used containers to be cleaned and sterilized for the

next crop. 

In smaller nurseries, the process of extracting plants from

their containers, grading, and packaging them is often

done at individual work stations. Each station is equipped

with a rack or clamp that holds the container block or

tray in place while the workers pull and grade plants

(Figure 7.3.7A). In larger nurseries, however, the sequence

of tasks is combined into “grading and packing lines”.

Connected by conveyors (Figure 7.3.7B), different workers

are responsible for extracting, grading, and packaging.

In addition to reducing labor costs, grading and packing

has become more mechanized because of the high incidence of workplace injuries. Many forest and conservation

plants have aggressive root systems and develop a firm plug

by the end of the growing cycle. Roots of some species

even grow into small holes in the walls of the container

cavities, especially with Styrofoam® blocks. This makes

extracting plants by hand difficult, and nursery workers on

the packing line often develop tendonitis and other chronic

wrist and lower arm injuries. To facilitate extraction, some

nurseries use mechanical “thumpers” that use a jolting

motion to loosen the plugs from their containers (Figure

7.3.7C).

Another reason that plants are difficult to remove from

containers is that roots often grow out of the drainage

hole and form a mat (Figure 7.3.7D). To facilitate extraction, some nurseries run the container blocks over a rotating blade to sever the root mat (Figure 7.3.7E). It is much

easier to prevent this by designing greenhouse benches

that promote air-pruning of roots. 

The extent of mechanization of the packing line varies by

nursery size and sophistication. Larger nurseries often use

pin or rod extractors to physically push one row of plants

at a time from the container and onto a conveyor belt

where they are graded (Figure 7.3.8A). Culls are discarded off the conveyor whereas shippable plants are counted

into bunches of 5 to 25. At the end of the conveyor,

another worker collects the bunches and packages them. 

7.3.5.3 Packaging Plants

Three common packaging systems are used for native

plant nursery stock. 

Jelly-rolling. In this process, bunches of plants are placed

in a cradle and their root plugs are tightly wrapped with a

protective material (Figure 7.3.9A). The jellyroll bundles

and then stacked into carboard boxes for storage and shipment to the outplanting site (Figure 7.3.9B). Jellyrolling has

been used for decades to protect the fine roots of bareroot

stock from desiccation (Dahlgreen 1976), and research has

shown that moisture stress is lower for jelly-rolled conifer

stock (Figure 7.3.9C). Wet burlap and absorbent paper

toweling was traditionally used but cellophane is preferred

for native plants that do not form a durable root plug. A

field trial with bur-sage (Ambrosia dumosa) seedlings

found that jellyrolling improved their moisture status during shipping and outplanting, and that they survived and

grew as well as plants shipped in containers (Fidelibius

and Bainbridge 1994). The most obvious advantage of jellyrolling is that containers are not damaged or lost during

the outplanting process. For polybag plants grown in

native forest soil, shaking the soil from the root system,

dipping the roots into a superabsorbent slurry, and jellyrolling greatly reduced the volume and weight of pine

seedlings. In addition, it allowed the soil-based media to

be sterilized and reused, saving the cost of procuring more

media and the impact on the forest environment (Mexal

and others 1996).

With the recent interest in shipping frozen nursery stock

to the outplanting site, jelly-rolling single plants keeps

them from freezing together. 

Bagging and boxing. In the second packaging system,

automatic bagging machines hold a supply of plastic bags

that are automatically inflated by a flow of air, making it

easier to insert plants (Figure 7.3.8C). Generally, when

bags of plants will be placed into plastic-lined boxes for

storage, as is the usual case for contract crops, then the

bags are just deep enough to enclose the root plugs to

facilitate handling. When bundles of plants will be stored

in bulk bins (Figure 7.3.10A), as is often the case for spec-
92

Figure 7.3.7—Each grading station in the “pull and wrap”

operation has a rack to secure the containers (A). In larger

nurseries, grading stations are part of grading and packing

lines which increase efficiency (B). Because plants are often

difficult to pull from containers such as the StyroblockTM,

they are first run through a “thumper” that loosen the plugs

(C). If roots have formed a mat at the drainage hole (D),

they must be trimmed to ease extraction (E).

A

B

C

D

E
93

Figure 7.3.8—In more mechanized nurseries, plants are pushed from their container one row at a time by a pin extractor (A).

After grading, plants are counted into bundles that are either wrapped in cellophane (B), or placed into a plastic bag (C). In

the final step, bundles are placed into cardboard or plastic boxes that protect the stock during storage and shipping (D).

ulation crops, then the bags are large enough to enclose

the entire plant, especially for evergreen crops, to retard

desiccation (Figure 7.3.10B).

Boxing. In this third process, which is commonly used in

the southern United States, container plants that are going

to be hot-planted are often extracted and placed directly

into shipping boxes without any type of plastic bag

(Dumroese and Barnett 2004). These plants are lifted,

stored for a very short time in a cooler, and outplanted

before transpiration and desiccation reduce plug moisture

to an unacceptable level.

The final step in the grading and packing process involves

placing the plant bundles into storage or shipping boxes or

bins (Figure 7.3.8D), and marking them with the species,

seedlot, number of plants, and other important information.

7.3.5.4 Processing large volume container stock

Because of their size and weight, large container stock

are typically processed one at a time and accumulated in

a shadehouse or open compound until they can be

shipped (Figure 7.3.11A). Although large ornamental

nurseries often store their stock under refrigeration, this is

not common in forestry or native plant nurseries. Square

containers, such at TreepotsTM, are graded and stored in

special metal pallet racks or in plastic crates (Figure

7.3.11B) until they can be shipped for outplanting.

The typical storage box is made of corrugated cardboard

that has been treated with plastic or wax to make it

waterproof (Figure 7.3.12A). Some nurseries use corrugated plastic boxes that, although they are more expensive,

are reusable (Figure 7.3.10B). Even nurseries that ship

A C

B D
94

Figure 7.3.9—Jellyrolling consists of lining up plants on a

cloth, paper or cellophane wrapper, folding the material

over the roots, and then rolling the plants into a bundle (A).

Besides protecting the root plug during storage, shipping,

and outplanting (B), research has shown that jellyrolling

reduces plant moisture stress (C). (C modified from

Lopushinsky 1986).

A

B

C
95

Figure 7.3.10—When crops will be bulk-stored for later repacking and shipping (A), plants are

completely inserted into deeper plastic bags to retard desiccation (B).

Figure 7.3.11—Large container plants are often graded in the shadehouse (A) and stored on

racks until they can be shipped (B).

A B

A B
96

Figure 7.3.12—Waxed cardboard boxes make handling

easier and storage more efficient (A). A plastic bag liner (B)

is absolutely essential for long-term freezer storage because

moisture is drawn out of plants and condenses on the side

of the containers (C).

stock to the outplanting site in the growth container often

put stock in boxes for additional protection against

mechanical injury. Boxes are the standard for refrigerated

storage of pull-and-wrap container stock but, because

they are not moisture-proof, a thin (1 to 2 mil) plastic bag

liner is needed (Figure 7.3.12A). With freezer storage, this

thin plastic bag liner (Figure 7.3.12B), is mandatory to

prevent desiccation injury because refrigeration equipment continually removes excess moisture from the storage rooms (Figure 7.3.12C). 

7.3.6 Packaging for Storage and Shipping

A

B

C
97

At each grading station, cull plants are dropped on the

floor or tossed into a bin. If there is a market, undersized

but otherwise healthy plants can be transplanted into larger containers. This is common with cultivars that can be

outplanted over a large geographic area, or for threatened

or endangered species where every plant is valuable.

Most forest and conservation plants come from a specific

seed zone (“source-identified”), however, and so are only

adapted to a rather restricted area. In addition, most

forestry and native plant projects outplant all their stock

in one season and so there is no market for hold-over

plants.

Therefore, most nurseries compost their culls for reuse as

a soil amendment. Because the woody stems and roots

would take years to decay, culls are run through a hammer mill or tub grinder to hasten decomposition and

speed-up the composting process (Figure 7.3.13).

7.3.7 Processing Cull Seedlings

Figure 7.3.13—Cull plants can be ground in a tub grinder

and composted.
98

7.3.8 Summary and Conclusion

Plants may be harvested, graded, packaged, and stored in a

variety of ways depending on the timing of the outplanting

window, the type of container used to produce the plant,

and the convention used in a particular locale developed

through research and/or experience. Plants harvested during the growing season with minimal dormancy and stored

for just a few days with or without cooler storage are said

to be “hot-planted.” More often, plants are harvested when

dormant and stored for a few weeks to months in 

refrigerated storage. Nursery managers can determine

when plants are dormant using the calendar, visual clues of

the plants themselves, outplanting trials, or plant quality

tests. Calculating chilling sums for a crop and correlating

that with the results of plant quality tests is probably the

best way for managers to ensure crops are dormant prior to

harvesting.

Many factors influence the harvesting process, including

nursery size and mechanization, customer base, container

type, plant growth form, whether plants are extracted or

not and subsequently placed in bags or jellyrolled, storage conditions, and local success derived from research

and/or experience. For example, state and private nurseries often grow plants on speculation; those plants are

extracted from containers, bundled in groups consistent

with minimum orders, bulk-stored in coolers, and then

packaged for shipping as orders are received. Conversely,

large, reforestation nurseries usually grow plants on contract, extract them from containers, and store them in

coolers or freezers by contract until outplanting, unless

those nurseries are in the Maritimes of Canada where

plants are retained in containers and stored in outdoor

compounds. Many native plant nurseries grade and ship

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