Last revised February 3, 2010
Commercial greenhouse vegetable production is an exacting and costly enterprise. Only expert management can prevent large-scale financial losses. Publications providing general information are available from libraries. Although several companies offer package investment opportunities, supplying equipment, materials and advice, none of these can guarantee success. In greenhouse production there is no substitute for experience.
Excellent publications with in-depth information are:
Papadopoulos, A.P. 1994. Growing Greenhouse Cucumbers in Soil and in Soilless Media. Research Station, Harrow, Canada. Publication 1902/E. Communications Branch, Agriculture and Agri-Food Canada. Ottawa, ON K1A 0C7.
British Columbia Ministry of Agriculture, Fisheries, and Food. Greenhouse Vegetable Production Guide for Commercial Growers. 808 Douglas St., Victoria, BC V8W 2Z7.
Depending on the number of units purchased, double polyethylene greenhouse costs in 1994 would run about $7.00 to $8.00 per square foot. Hydroponic equipment will cost another $1.50 to $2.00 per square foot. Land cost, site preparation, foundations, concrete floors and electric, water and gas service may cost another $4.00 to $5.00 per square foot. A number of different materials are used in greenhouse structures and coverings, which can result in a wide range of total construction costs. This guide does not address greenhouse engineering or coverings.
Cucumbers grow more rapidly than tomatoes and produce earlier. "English" or "European" cucumbers are the seedless (parthenocarpic), or all female (gynoecious) varieties that are used for greenhouse production. They produce higher yields and do not require bees for pollination. They are distinctly different from conventional slicing cucumbers, so you should determine if a suitable market exists in your area before production. However, because this type is so different from the conventional slicing cucumber, some market can be found almost all the year round.
Greenhouse cucumber. Photo credit: Bill Mansour, Oregon State University
Varieties commonly used in British Columbia, Canada are Jessica, Optima, and Flamingo (mildew tolerant). Other varieties that have been grown in the Pacific Northwest are: Corona, Sandra, Fidelio (powdery mildew tolerant), Fertila, Factum, Femspot, Femfrance, LaReine, Pepinex'69, Pepinova, Pandorex, Santo. Toska 70 has been a high yielding, high quality, seedless cucumber cultivar that is not all-female but still does not require bees. For trial: C949 (similar to Corona).
Conventional cucumber varieties require bees for pollination. Bees pose management problems in winter greenhouse production, and the prices for conventional cucumbers do not justify greenhouse production.
Cucumbers require higher temperatures than tomatoes so they are generally grown as a spring or early summer crop.
Two to three crops may be grown per year. Yields would be the same but fruit quality is usually better with a three crop system. Planting dates are usually in December and June for a two crop system and December, May, and September for a three crop system.
Use three week old plants that are free of disease and insect infestations.
Accurate temperature, humidity, and carbon dioxide control are important. If a greenhouse is kept completely closed to conserve heat during long periods (several days at a time) you should provide suitable carbon-dioxide in the greenhouse atmosphere. Management of irrigation to control increased humidity and disease problems also become critical in closed houses.
For more information on greenhouse environmental control, see the file Florida Greenhouse Design.
Temperature requirements for major greenhouse vegetables differ between vegetables and stages of growth. For cucumbers, temperatures should be kept between 75 and 77 F during the day and 70 F at night until the first picking. When picking starts, reduce temperatures 2 degrees. After picking is started, night temperatures may be reduced 2 degrees per night gradually to 63 F temporarily (for 2-3 days) to stimulate growth. Exceeding maximum temperatures temporarily can be used to cause some flower abortion and maintain the fruit-vine balance.
In general, cooler temperatures are used when light intensities are low.
Carbon Dioxide Enrichment:
Addition of carbon dioxide to greenhouses has been demonstrated to improve vegetable yields. Carbon dioxide is normally present in the atmosphere at a concentration of 330 parts per million. Concentrations of 1,000 to 1,500 ppm in greenhouse atmospheres have given the best results. Increases of 20 to 40 percent in yield have been reported for various vegetables. Generating and monitoring equipment is readily available. Many different types are in use. Investigate the various models and types before purchasing.
Tailor fertilizer programs for specific crops and soil fertility situations. Proper fertility is necessary for success. Plants have different fertilizer requirements during different stages of their growing cycle. Whether you use soil or a soilless system, no single set of recommendations will apply.
Production in soil:
Use soil tests to determine initial applications, and monitor fertility levels by leaf analysis throughout the growing season. Both soil tests and leaf analyses are available through Oregon State University Extension offices.
For production in soil, a routine fertilizer program would be the addition of 0-20-20 fertilizer at 1,000 to 2,000 lb/acre before the fall crop, and 650 to 1,000 lb/acre before the spring crop or, you can supply phosphorous by applying 46 percent triple superphosphate at 300 to 500 pounds per acre and potassium by using potassium sulfate at 300 to 400 pounds/acre.
Add N as ammonium nitrate, calcium nitrate, or potassium nitrate before planting and throughout the season, depending on the amount of organic matter in the soil. Feed weekly with solutions of balanced fertilizers.
In general, cucumbers are heavy feeders. Large quantities of manure, up to 70 tons per acre on poor soil, are often used. Phosphorous is added at 800 to 1,000 lb superphosphate/acre as a preplant treatment. Cucumbers may need a weekly feeding with balanced solutions of such fertilizers as 10-52-17, 15-30-15 or 20-20-20, with amounts best determined by tissue analysis.
Hydroponic culture is the growing of plants in gravel, sand, or artificial soilless mixes in troughs, tubes, or tanks suitably built to allow circulation of the nutrient media. Soilless culture is more demanding and less forgiving of mistakes than conventional soil culture. Good nutrient media composition and balance are important.
Hydroponic methods allow production of vegetables in areas where suitable soil is not available or where disease or other conditions make ground bed production unfeasible. Although you can automate this system to minimize irrigation and fertilization labor input, continuous monitoring of all aspects of plant growth and culture media, nutrient balance and a thorough understanding of the crop and its physiology is critical. Costs of the automatic devices and special nutrient media are substantial. All other aspects of production remain the same as with conventional culture. There are no yield or quality advantages over conventional production if the quality of management is equal. None of the package offers of equipment and technical services for hydroponics guarantees success. Investigate thoroughly before making substantial investments.
Due to environmental concerns, restrictions may be in place regarding the disposal of excess fertilizer solutions and growing media. Possible options are to discard fertilizer solutions by using it on pastures or in other agricultural applications, and to recycle growing media by blending it with other potting mixes or agricultural soils. Consult appropriate agencies for available options.
Excellent books on this subject are:
Hydroponic Food Production by Howard M. Resh, Woodbridge Press Publishing Company, Santa Barbara, CA 93160.
A Guide for the Hydroponic & Soilless Culture Grower by J. Benton Jones, Jr., Timber Press, POB 1631, Beaverton OR 97075.
Greenhouse Vegetable Production Guide for Commercial Growers 1993-1994 Edition. British Columbia Ministry of Agriculture, Fisheries and Food., 808 Douglas St. Victoria, British Columbia, Canada V8W 2Z7.
Two major soilless culture systems are used, those in which plant nutrients are recirculated (closed-system hydroponics), and those that utilize artificial media to anchor plant roots but new nutrient solution is constantly provided to the plants and the excess nutrient solution is not collected and recirculated (open-system hydroponics or bag culture).
Closed-system hydroponic culture is the growing of plants in troughs or tubes, where plants are anchored in gravel, sand, or artificial soilless mixes; or without artificial media for anchor, such as nutrient-film technique (NFT). Any system used must be suitably built to allow proper application and recirculation of the nutrient media. Flow rates of 1.5 to 2 quarts per minute are most common. In a closed-system, the nutrient solution is regularly monitored and adjusted for pH as needed. Because plants take up nutrients at different rates, and roots exude certain chemicals, imbalances and problems can occur. To prevent undesirable build up of certain elements, the nutrient solution may need to be changed every 2-3 weeks with changes as often as once per week during periods of peak growth. By careful, daily monitoring of nutrients in solution and, especially, the electrical conductivity (EC), and by installing activated charcoal filters to remove certain toxic root exudates, a large reservoir of nutrient solution may be maintained for one crop cycle (up to 10-11 months). The EC should be maintained at 2.2 during low light intensity and 2.5 as light intensity increases. Do this by adding fresh water when EC exceeds 2.5 and new, complete nutrient solution is added to bring the EC to 2.5.
Bag Culture uses artificial media (usually rockwool) packaged in 3 or 4 cubic foot bags. Rockwool comes in two densities, standard and low density. The low density is used for one year and discarded. The standard density may be sterilized and reused for up to three crops. Two common trade names are Redi-Earth and Metro-Mix. The 4-cubic-foot bags are best for cucumbers. Two rows of cucumbers are usually planted per bag with plants spaced 16 inches apart in each row with rows 16 inches apart. Bags are placed in rows 6 feet apart, and spaced down the row to allow a uniform 16-inch spacing between plants. A drip irrigation system with spaghetti drippers for each plant is used to distribute the nutrient solution. A 10%-20% excess solution is applied during cloudy cool periods and 25% to as high as 50% under sunny, warm conditions to provide drainage and prevent salt buildup. This excess should be collected and discarded or may be reused with certain restrictions.
Common modifications of this system (to reduce cost) utilize 3-5 gallon plastic bags or pails with saw dust, pine bark or rice hull media. Western Hemlock and Douglas-fir are most commonly available and the main ones used in the Pacific Northwest. Avoid western red cedar because of possible toxicity from chemicals in it. Use a medium-fine grade of horticultural grade (guaranteed to be free of toxic chemicals that may be used by the lumber industry). If too fine a grade, the saw dust will limit oxygen exchange as it breaks down resulting in root suffocation. Before using saw dust, test leachate conductivity for any salt accumulation and leach bags with fresh water if needed. Modifications of the fertilizer program are necessary to compensate for specific media. Of particular concern is possible manganese toxicity since manganese can accumulate in wood to toxic levels. Check the first leaf tissue samples and adjust manganese applications as needed.
Commercial fertilizer mixes are available through horticultural supply companies. Follow directions carefully in preparing and dispensing the nutrient solution. Choose a high quality fertilizer injection pump and system to minimize fertilizer distribution problems. The major advantage of bag culture is the reduced management of nutrient solution monitoring, and the elimination of nutrient circulation, that is required in "closed" hydroponic systems.
Six to nine square feet of space per plant is required, depending on the variety and cropping system See also additional information on spacing under the various production systems described (above).
Plants need to establish a strong root system and vegetative stem before fruit is allowed to set. All lateral branches, flowers, and tendrils should be removed until the plant has 8-10 leaf nodes. Twist the support string around the plant as it grows, always in the same direction.
After 8-10 leaf nodes have developed, allow one female flower to set at each subsequent node. Remove any damaged or crooked female flowers (no male flowers should be present with gynoecious varieties). Also, no pollination is necessary with parthenocarpic types. Remove all lateral branches, training the plant to a single stem, and remove bottom leaves as new leaves form on the upper portion of the stem, leaving 50-60 inches of green, healthy leaves.
When the plant reaches the support wire, several pruning options are used. The most common is to allow the plant to grow along the support wire about 12 inches, or two leaf nodes, toward the next plant. Allow a lateral to grow at each leaf node. The terminal and each of the laterals are allowed to grow another 30 inches, hanging from the wire, then pinched to terminate growth. When the fruit from the terminal and each of the laterals is harvested, remove these three hanging branches in turn, and allow three new terminals to grow from the main stem at the support wire. Repeat the process until the crop is terminated.
If mulches are used, apply to the soil when cucumbers are about two feet high. Straw mulch is common, used at about 200 bales/acre. The mulch reduces evaporation of water from the soil and prevents compaction of the surface. Where a hydroponic system is used, white plastic may be placed on the soil surface for sanitary reasons and for greater light reflectance.
Maintain an adequate supply of water to plant roots. Excess water reduces soil aeration. Young plants put in the greenhouse in mid-winter may need to be watered only once every 10 to 14 days. The same plants in mid-summer may need water daily, requiring an estimated 1/4 to 3/4 gallon per plant per day, depending on size.
With good management, greenhouse cucumbers will produce from 20 to 30 pounds of fruit per plant over a 4-month harvest period.
For highest returns, thoroughly harvest marketable fruit at regular intervals. Remove cull fruit so other fruit can develop properly. During warm weather conditions, cucumbers may grow very rapidly and it is important to shorten harvest intervals.
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Cucumbers can be held 10 to 14 days at 50 to 55 F with a relative humidity 90-95%. They are subject to chilling injury if held longer than about 2 days at temperatures below 50 F. At temperatures of 50 f and above, they ripen rather rapidly, the green color changing to yellow. This color change starts in about 10 days at 50 F and is accelerated if the cucumbers are stored in the same room with apples, tomatoes, or other ethylene-producing crops. Modified atmospheres, particularly with low oxygen (5 %), will retard yellowing.
Cucumbers are vary susceptible to shriveling; hence, the humidity in the storage should be kept high. Cucumbers for the fresh market are usually waxed to reduce moisture loss. Shrink-wrapping with polyethylene film can also delay the loss of turgidity.
Symptoms of chilling injury are water-soaked spots, pitting, or tissue collapse. A surge in ethylene production may occur and extensive decay will develop when chilled cucumbers are removed from low-temperature storage.
Slicing cucumbers are commonly packaged in 55-lb (l-l/9 bushel) cartons and wirebound crates; 47 to 55-lb bushel cartons and wirebound crates; 26 to 32-lb cartons, or 28 to 32-lb L.A. lugs.