SELECTING CROPS TO GROW

The high cost of producing certain plant species in northern regions during the winter has driven some greenhouse operations out of busi­ness and drastically altered the selection of crops grown by others. In addition, increasing competition from growers in other countries and the desire by retail florists to use more uncommon flower species in their arrangements have caused an overhaul of greenhouse crop choices in all parts of this country. The industry is definitely in a state of transition. Growers who once raised extra quantities of bedding plants, chrysanthemums, and poinsettias on the chance that they might sell, and because the space was available, are now growing for contracts only and shutting down all or part of their operation until time to start the next contracted crop. Other growers are changing from warm crops (mums, roses, poinsettias) to cold crops (carnations, cyclamen, kalan – choe) to reduce their energy costs.

Perhaps motivated by increased energy costs, yet still to the long­term benefit of both grower and the consumer, growers are trying new plant products. Crops formerly grown only as bench crops, such as carnations and snapdragons, are now being produced as potted plants because they are cold crops. Lilies once grown only in the garden are finding their way into greenhouse production and flower shops.

The future will probably see more varieties in the northern green­house, not fewer, and they will replace some old favorites, now too costly to produce except in warmer regions. The new varieties can be predict­ed to require lower temperatures for production, less light, and perhaps greater manipulation of photoperiodic response by the grower.

Table 20-3 summarizes the production requirements of some com­mon greenhouse crops. It is neither a complete listing of all greenhouse crops nor a comprehensive guide to the culture of the plants. It is intended merely as an introduction.

Spacing

Shading

Growth

Retardant

Pinching

Disbudding

Special Requirements

Fixed at 10X10 inches for forcing

Some cultivars initiate buds best under short-day conditions.

B-Nine or Cycocel for flower bud initiation

Used to increase flow­ering shoots during first year; shear­ing needed to shape plants for sale during second year.

Buds are not removed, but wild growth around flower buds should be removed.

An acidic soil is needed with a pH of 5.0 to 5.5. Azaleas are grown in pure sphagnum moss or a mix of sphagnum and sand. The soil should be low in fertil­ity, but iron and manganese must be added.

One plant per pack cell or pot.

Unnecessary

Varies with species

Sometimes done to encourage branching and to prevent leg­giness in plants before sale.

Unnecessary

New seedings must be kept moist and not allowed to overheat. No drying is allowable after germina­tion. If not direct seeded, they should be transplanted as soon as possible. The

transplant hole is made with a dibble for pots and a dibble board for molded plastic packs. Also can be automated.

Expanding

Unnecessary

Unnecessary

Unnecessary

Unnecessary

High light intensity improves plant quality.

Expand­ing to 4X4 inches

Heavy shade needed in sum­mer; none in winter

Cycocel needed for some culti – vars

Unnecessary

Unnecessary

Seedlings are transplanted to flats for further growth and finally to pots. Cal – celaria is a long-day plant. Extended days in the winter can promote flowering

Fixed at 6X8 inches

Unnecessary

Unnecessary

Once or twice; second pinch not as extensive

Side buds are removed as soon as they form.

The plants must be sup­ported by wires as they grow. The wires are raised as the plants grow. Pinch­ing should occur at the first nodes to elongate. When harvesting, cut stems at a length that allows 2 or 3 nodes to remain.

Chrysanthemum Benched 60°-65° F 60° F Cuttings to prop­

agate; often pur­chased as rooted cuttings to avoid virus disease problems

Chrysanthemum Potted 62°-63° F 62°-63° F Same as benched Same as benched chry-

chrysanthemum santhemum

Cyclamen

Potted

Ll_

о

LO

CD

1

о

LO

LO

Ll_

о

LO

LO

1

о

О

LO

Seeds to propa­gate; often purchased as partially grown plants to reduce length of time in greenhouse

Twelve to fifteen months if started from seed

Daffodil

Potted

55°-63° F to force

55°-60° F to force

Bulbs

Up to twenty weeks required; precooling

for four to five weeks; eight to twelve weeks for rooting; ten days to three weeks for flower­ing after rooting

Foliage plants Potted 80° F 70° F for pro – Seed and assorted Four weeks or more

duction; 60° F asexual methods after rooting and trans­prior to sale depending on planting

species; stem and leaf cuttings

Spacing

Shading

Growth

Retardant

Pinching

Disbudding

Special Requirements

Fixed at

Mums set flower

Unnecessary

Multiple-stem

Spray mums

The plants must be sup-

7X8 inches

buds when given

plants are

are not dis-

ported by wires as they

(standards);

twelve hours or

pinched one

budded. Sin-

grow. The wires are raised

6X7 inches

less light each

to three weeks

gle-blossom

as the plants grow. Lights

(pom-pons)

day. Artificial

after planting.

mums are

must be used from August

light used to pre-

Single-stem

disbudded

to May to provide long

vent flowering at

plants are not

as soon as

days. Black cloth must be

certain seasons

pinched

the side buds

used from mid-March to

and stages of

form.

August to provide short

growth; shade

days. During the summer,

cloth used to

high temperatures beneath

induce flowering

cloth should be vented to

at other stages and seasons.

prevent flower abortion.

Expanding

Same as benched

B-Nine or

Plants are given

Remove side

Cuttings are planted at an

to 15X15

chrysanthemums

Phosfon or

a soft pinch

buds to allow

outward-directed angle

inches

A-Rest

to promote

one bud per

(about 45°) to create a

at least three

stem as soon

fuller and more shrub-like

breaks from

as buds form.

plant. There are usually five

each cutting

cuttings per 6-inch pot.

Expanding

Unnecessary

Unnecessary

Unnecessary

Unnecessary

To promote flowering, the plants must be a bit pot- bound and the soil kept on the dry side. They will flower about ten weeks after their final potting. Avoid high fertility.

Fixed with

Unnecessary

Unnecessary

Unnecessary

Unnecessary

Bulbs may be precooled

pots touch-

at 48° F. Storage may be

ing

outdoors or in controlled refrigeration. If not pre­cooled before planting, time must be provided during the rooting period. Temperatures are gradually reduced during the rooting period from 48° F to 32° F. Bulb suppliers can provide specific schedules.

Expanding

Most foliage

Unnecessary

Usually unnec­

Unnecessary

Accelerated growth is

plants require

essary

possible with high humid­

partial shading.

ity, heavy watering, and frequent fertilization. The plants must be hardened – off before sale.

Spacing

Shading

Growth

Retardant

Pinching

Disbudding

Special Requirements

Expanding

Light shade

Unnecessary

Stock plants

Unnecessary

Fans in the greenhouse will

to allow

needed to pre-

pinched to

keep disease down. Flowers

good ven-

vent blossom

promote shoots

should be picked off while

tilation

burn

for cuttings;

the plants are in produc-

between

production

tion.

plants;

plants given

crowding

a hard pinch

promotes

about four

disease

weeks after potting and a soft pinch four weeks later

Expanding

Saran or light

B-Nine or

Unnecessary

When

Plants should be watered

to 12X12

greenhouse shad-

Cycocel

the plant

carefully to avoid wetting

inches

ing compound

becomes well

the crown. Flower forma-

budded, the

tion is diminished if the

first two buds

crown remains wet over­

to show color should be removed for a more uniform plant.

night.

Expanding

Outdoor growth

B-Nine or

A hard pinch in

Unnecessary

Heavy irrigation and high

to 14X14

best under partial

Gibberel-

mid-summer

humidity are needed for

inches

shade

lic Acid or

best outdoor growth. Alu­

Ancymidol

minum sulfate is used to turn the pink flower color to blue. Soil should be slightly acidic.

Fixed with

Unnecessary

A-Rest

Unnecessary

Unnecessary

Greenhouse temperatures

7 inches

may need to be altered as

between pot

the time of sale approaches

centers

to accelerate or slow the time of bloom. Tallest plants must be kept in the center of the bench and all plants must be rotated to prevent stem curvature.

A Comparison of Selected Floriculture Crops (Continued)

Crop Pot or Bench Day Night Method of Production Time

Crop Temperature Temperature Propagation Required

Poinsettia

Potted

Ll_

о

LO

CO

1

о

О

со

60°-64° F

Cuttings; often

Three weeks to root

purchased as

cuttings; about eleven

rooted, unrooted,

weeks from potting to

or callused cut­tings

sales

Rose

Bench

Ll_

о

О

r-"v

і

о

LO

СО

60° F

Budding; graft-

Five to eight weeks for

ing; cuttings

a flower to develop after a stem is pinched

Snapdragon Bench 60°-65° F 50° F Seeds Fifteen weeks for sin­

gle-stem crops; nine­teen weeks for pinched crops

Tulip Potted 68° F 60°-63° F Bulbs Fourteen to eighteen

weeks for precooling and root formation; about three weeks for flowering

Spacing

Shading

Growth

Retardant

Pinching

Disbudding

Special Requirements

Expanding

Black shade cloth

Cycocel or

Required in

Unnecessary

Molybdenum deficiency

to 15X15

may be necessary

A-Rest

second week

is common and must be

inches

from October 1

after potting if

anticipated and offset by

to 21 to ensure

multiflowered

the fertilizer formulation.

a fourteen-hour

plants desired;

dark period for

four or five

bud set. Before

nodes should

that, a two-hour

be left below

lighting in mid­night will keep the plants veg­etative.

the pinch.

Fixed at

Greenhouse

Unnecessary

Young plants

Unnecessary

Plants must be supported

12 inches

shading com-

pinched to

in the bench. Mulch must

between

pound needed

promote shoot

be applied during the sum-

centers

during summer

development;

mer. Roses must be cut

mature plants

twice a day before they

pinched to

open. Flowers are kept in a

promote flower

cooler (45° F) in water until

development; all pinches above a five – leaflet leaf

grading and sales.

Fixed at

Green house

Unnecessary

Only pinched if

Unnecessary

Plants must be supported

4X5 inches

shading com-

multistemmed

in the bench.

for single-

pound needed

plants desired

stemcrops and 7 X 8 inches for pinched crops

during summer

Fixed with

Cover with news-

A-Rest for

Unnecessary

Unnecessary

Bulbs are placed into pots

pots touch-

paper during

certain cul-

or pans with tips even with

ing

first few days of

tivars

the rim. A reservoir for

forcing to stretch

water should be left in each

flower stems.

container.

SUMMARY______________________________________

To meet the requirements of a fluctuating market and minimize losses due to over- or under-production, greenhouse growers plant, care for, and harvest their crops in accordance with production schedules. Accurate records aid in determining whether to increase or decrease the production quantities of previous years. Production schedules are frequently altered by changes in the weather and require the immediate attention of the growers to get the crops back on schedule.

Greenhouse soils differ greatly from field soils. They often are totally artificial. To be most useful to the greenhouse grower, the growing media must be predictable. Predictability is the major advantage of the artificial media.

The growing media are pasteurized to eliminate undesirable micro­organisms, insects, or weeds. Pasteurization is usually accomplished with steam applied from the surface, from pipes buried in the soil, or in closed containers. Chemical pasteurization is also possible using chemical fumigants.

Regular soil testing is an important part of a greenhouse production schedule. Soil tests are needed for three reasons: to check the pH, to check for nutrient deficiencies, and to measure the soluble salt content. Soil tests kits are available for personal use, or tests can be performed by the state’s college of agriculture or commercial laboratories.

The containers used for greenhouse potted crop production vary depending on the crop being grown and the time of year. They include pots, pans, and azalea pots in clay, hard plastic, or styrofoam; peat pots and strips; molded plastic packs; hanging baskets; and flats.

Greenhouse crops are reproduced from seeds, runners, bulbs, and cuttings; and by layering, grafting, budding, division of the crown, and tissue/organ culturing. Propagation of the stock may be done by spe­cialized propagation firms or by the greenhouse growers who will grow it to maturity.

Different methods of growing require different techniques of spac­ing. Both expanding spacing and fixed spacing have their uses depend­ing on the crop and the production schedule. Labeling methods vary, too, and are important for the identification of cultivars, flower color, date of planting, and date of harvest.

Irrigation is the maintenance of a proper balance of moisture and air in the growing media. Irrigation techniques are not the same for all crops, nor are they uniform for a single crop throughout the year. Both hand-watering and semiautomatic watering systems have their place. The watering system can also be used to apply fertilizer to the crops by means of injection devices. An alternative is the use of fertilizer in dry form.

Since greenhouses provide a near-optimum growing environment for plants, it is predictable that plant pests can flourish as well. Pest con­trol must be a regular part of the greenhouse production schedule. The principles of control (exclusion, eradication, protection, and resistance) must be applied continuously. Specific recommendations for green­house pest control are available from state colleges of agriculture and the local Cooperative Extension Service. All chemical pesticides must be applied in accordance with strict safety standards. With increased concern about the overuse of pesticides and the resulting governmental

regulations, more and more growers are relying on biological controls and integrated pest management programs to provide the profitable control of pests that they require.

Greenhouse crops are being grown more cautiously than in past years. High fuel costs, stronger competition from sources worldwide, and an increasing demand for more unusual flowers have caused more growers to seek contractual agreements before planting and to change the crops they grow to reduce energy costs and satisfy con­sumer preferences.

ACHIEVEMENT REVIEW

A. TRUE/FALSE

Indicate if the following statements are true or

false.

1. Floral crops are seasonal in their appeal to consumers.

2. Certain consumer demands can be anticipated by a grower.

3. Crop production scheduling is a total guessing game each year.

4. The environment outside the greenhouse has no appreciable influence on the crop production schedule.

5. Economic trends in the local market area influence the crop production schedule.

6. Irrigation should be sufficient each time to allow some water to drain from the pot or bench.

7. Plants should never be permitted to surface-dry.

8. Pots should be filled to the rim with soil.

9. Bench crops do not dry out uniformly, but potted crops do.

10. Fertilizers and pesticides can be applied through the irrigation system.

11. Plants should be watered in the evening for greatest benefit.

12. Less liquid fertilizer than dry fertilizer must be applied for the same effect.

13. The amount of fertilizer applied through an injection system is determined by the strength of the concentrate and the dilution ratio of the injector.

14. Injector fertilizers contain dyes to provide a check of the dilution accuracy.

15. Growth retardants are applied through the irrigation system.

B. MULTIPLE CHOICE

From the choices given, select the answer that best completes each of the following state­ments:

16. The elimination of all life in the soil is

termed________ .

a. protection c. pasteurization

b. sterilization d. steam treatment

17. The elimination of undesirable microbes, insects, and weeds from the soil is termed

a. protection c. pasteurization

b. sterilization d. steam treatment

18. Pasteurization is accomplished with

a. steam c. steam or

b. chemicals chemicals

d. solar radiation

19. Steam can be applied to a bench of soil

either_________ or________ .

a. in canisters/as hot water

b. from the surface/through buried pipes

c. through vented pipes/in aerosol cans

d. by hand/by machine

20. A disadvantage of chemical fumigants is

their__________ .

a. toxicity c. both of these

b. waiting time d. none of these

C. SHORT ANSWER

Answer each of the following questions as briefly as possible.

1. List two advantages and one disadvantage of using artificial soils for greenhouse crop production.

2. List three reasons why greenhouse growers need soil tests.

3. List the options available to a greenhouse grower when a soil test is needed.

4. Match the types of containers on the left with the description on the right.

a. clay pots

1. specialized produc-

b. plastic

tion containers made

pots

of wire or plastic, and

c. peat pots

often containing a

d. pans

liner to retain the soil

e. molded

2. porous containers

plastic

whose height and

packs

diameter are equal

f. hanging

3. compartmented trays

baskets

used for both produc-

g. flats

tion and sale

h. azalea

4. shallow, rectangular

pots

trays without com-

partments; construct­ed of plastic or wood

5. biodegradable con­tainers that permit direct planting without removal of the con­tainer

6. clay or plastic contain­ers whose height is one-half their diam­eter

7. lightweight non­porous containers whose height and diameter are equal

8. round contain­ers whose height is three-fourths their diameter

5. Give some examples of greenhouse crops commonly reproduced by the following methods.

a. tissue and organ culturing

b. division of the crown

c. budding

d. grafting

e. cuttings

f. layering

g. bulbs

h. runners

i. seed

6. Indicate whether the following apply to expanding spacing (E) or fixed spacing (F).

a. less bench space required for immature crops than for mature ones

b. more transplanting required per plant

c. early root development limited by placement of small plants in large pots

d. used for bench crops

e. more handling and labor required

7. List the items of information that may be included on a bench label.

8. List the four principles of pest control.

9. List the protective clothing that should be worn when spraying highly toxic pesticides in a greenhouse.

10. List at least four alternatives to pesticides that can be used in a program of integrated pest management.

D. DEMONSTRATION

From Table 20-3 (A Comparison of Selected Floriculture Crops), select a group of crops that can be grown together in a single greenhouse. For that group, prepare production schedules that will keep the greenhouse in full produc­tion for an entire year. Provide for special sales at Christmas, Easter (April 5th), and Valentine’s Day. The production schedule for each crop should include the date of planting, transplant­ing, potting, staking, pinching, fertilizing, shad­ing, wrapping, disbudding, and growth regula­tor application whenever appropriate. It should also include the greenhouse temperatures, method of fertilizing and formulations of fer­tilizers, the spacing, and dates of expansion. Staking, wrapping, and dates of sales should also be included. Consult other references for necessary details.

OBJECTIVES

Upon completion of this chapter, you should be able to

• explain the differences between container and field nurseries.

• explain how plant species are selected for production and how quantities are determined.

• describe the concerns for media preparation.

• list the factors that determine how field nurseries are laid out.

• describe the methods of irrigating nursery crops and disposing of excess water.

• outline methods of fertilization, irrigation, and pest control for nursery production.

• label nursery plantings correctly.

• explain the techniques of pruning and field harvest.

• explain the use of cover crops and crop rotation in nursery production.

KEY TERMS

field nurseries ericaceous drum-lacing

container nurseries porosity cover crop

CONTAINER VERSUS FIELD NURSERIES______________

Nursery plants are produced in specialized production facilities under controlled, monitored conditions to maximize their rate of growth and standardize the quality of the harvested products. The product may be young plants that will be grown on by another nursery. Propagative materials such as grafts or liners (rooted, unbranched plants that will be grown to a larger size before sale) are examples of such young plants. The harvested product may also be plants ready for placement into landscape settings by landscape contractors or homeowners. Sizes of
such plants can range from partially grown to fully mature. It is in the methods used to produce this great variety of plant products that con­tainer nurseries and field nurseries differ.

Field nurseries are similar to crop farms. Plants are grown directly in the soil. These nurseries require sites with rich, well-drained soil, few rocks, a reliable and adequate fresh water supply, and proximity to transportation, usually a highway. Field nurseries traditionally produce trees and shrubs that require from one to ten years to reach the intend­ed size for harvest. Once installed in the field, plants are seldom moved prior to harvest. Therefore, field nursery growers must make careful decisions about spacing between plants and between rows in order to make efficient use of the land and allow field equipment to reach the plants during their production years.

Field nurseries are vulnerable to the uncertainties of nature. Care or harvesting of the crop can be brought to a costly halt when exces­sive rainfall renders the fields too wet for working. Also, due to the large acreages involved, winter injury and rodent, deer, and rabbit damage can be greater than in closed production facilities.

Container nurseries do not require fertile field sites. They do need level locations and may be surfaced with concrete, asphalt, or crushed stone. Like field nurseries, container production facilities need a good water supply and access to their markets.

Many of the same plants grown in field nurseries are adaptable to container production. However, some evergreens grow better under field conditions, and many deciduous shrubs can be produced faster and less expensively in the field. Usually plants produced in containers are kept in production for only one or two years and seldom longer than four years. Because container-grown plants have their root systems intact and suffer less from transplant shock, their acceptance in the marketplace is good. Current trends suggest that even higher percent­ages of nursery plants will be produced in containers in the future.