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.