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Cucumbers (greenhouse)

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Cucumbers are thought to have originated in India before their introduction to China and Europe some two millennia ago.

Although cucumbers are commonly considered a vegetable, they are technically categorized as fruits because they contain enclosed seeds and develop from a flower.

Generally established as transplants, greenhouse cucumber cultivars typically exhibit smooth skin and rounded ends and are longer and narrower than their conventionally grown counterparts.

Cultivation demands intensive care, including trellising, pruning, and a perpetual supply of water and nutrients. Although greenhouse production continues to rise in the United States, much of the annual cucumber supply comes from imports.

Types & Varieties
Cucumbers belong to the Cucurbitaceae family, which includes various gourds, pumpkins, watermelon, and squash.

For casual and commercial greenhouse cultivation, there are two primary types of cucumbers.

The first, referred to as a European, Japanese, or English cucumber, is the most popular due to its mild flavor, long length, and smooth delicate skin that does not require peeling. Most greenhouse growers prefer these seedless varieties for ease of use.

However, because skin dehydrates rapidly, they are often encased in plastic film. To reduce waste, some growers are turning to alternative methods (such as organic exterior coatings, similar to waxing) to prolonging shelf life and to eliminate plastic wrapping.

The second kind, the American slicing cucumber, contains seeds and features dark, bumpy, thick skin. Although they are smaller than their European cucumbers, their size renders them more conducive to canning or pickling.

The popularity of mini cucumbers continues to expand as they do not require plastic wrapping, their small size appeals to more consumers (especially children), and easier postharvest handling can facilitate better marketing.

SEASONAL AVAILABILITY
With rising domestic production and imports from Canada, Mexico, the Dominican Republic, the Netherlands, Spain, and other countries, greenhouse cucumbers are available year-round.

Varieties for greenhouse cucumbers differ regarding physical characteristics, pollination, and disease resistance.

Growers predominantly prefer Sandra or Toska 70, and Farbio, Corona, and Telegraph are also prevalent. Others growing in popularity include Carmen, Itachi (a white long Asian variety), Katrina and Picolino (mini, 4 to 6 inches in length), and Quirk (bite-sized).

Hybrid varieties feature increased disease resistance; common Canadian varieties include Jessica, Optima,
and Flamingo.

Other varieties grown in the Pacific Northwest include Corona, Sandra, Fidelio (powdery mildew tolerant), Fertila, Factum, Femspot, Femfrance, LaReine, Pepinex’69, Pepinova, Pandorex, and Santo.

CULTIVATION
There are several essential criteria for greenhouse soil, including low soluble salts, no soilborne diseases, and good drainage. As a result, sandy loam is superior to sand or clay.

Certain soilless methods, such as hydroponics, peat, perlite, coconut husk, and sawmill waste, are also successful in producing greenhouse cucumbers.

Seedless varieties germinate best from 80 to 82°F, whereas seeded varieties require 70 to 75°F temperatures for optimal germination. During the day, the soil temperature should remain between 70° and 75°F and, at night, about 65°F.

Once plants develop at least two true leaves, they are transplanted to the growing bed. After two to three weeks, plants should be relocated to the greenhouse, where a trellis system helps the plants grow quickly.

Trellis systems are generally categorized as umbrella, high-wire, or drape (or modifications thereof), and relate to pruning and production volume. Pruning stems, vines, and leaves promotes vigor and allows for better air flow and light but requires more labor and reduces capacity.

Heat and light are conducive to growth, as are nutrients and water. All should be continually monitored. Nitrogen, other nutrients, and ample moisture are carefully monitored, with temperatures between 75 to 80°F during the day for optimal growth.

For optimal harvest conditions, cucumbers should have a uniform diameter without yellowing on the blossom end. Typically, European cucumbers are harvested at a length of 12 to 16 inches and weigh from .75 to 1 pound.

To prevent the rapid moisture loss and softening endemic to thinner-skinned greenhouse cucumbers, shrink-wrap is recommended.

Proper storage climate is 52 to 55°F with 90 to 95% relative humidity; chilling injury can occur below 50°F, resulting in pitting and color loss. Exposure to ethylene also results in color loss, as fruit will yellow.


Pests & Diseases
Viruses, such as cucumber mosaic and watermelon mosaic, damage greenhouse cucumbers because no resistant variety has been developed.

Aphids often transfer these viruses to other crops and weeds, so properly situating greenhouses a half-mile or more from susceptible field crops, as well as managing any weeds will provide the best defense.

Powdery mildew produces white blotches about a quarter inch in diameter, first manifesting on the lower leaves. Air currents spread spores, meaning sanitation, fungicides, and resistant varieties constitute the best preventative measures.

Because grey mold only develops in humidity, air circulation and a properly climatized greenhouse to prevent moisture accumulation can preempt emergence.

Gummy stem blight, a fungus, affects the aboveground elements of the plant, creating light brown to black lesions which eventually kill the plant. Steam sterilization of soil, good sanitation, crop rotation, good ventilation, and fungicides are effective prevention measures.

Crooking, a physiological disorder, results from temperature, moisture, and nutrient imbalances and causes curvature of the fruit, hampering market value. Thrips can also cause crooking. Excessively curved fruit should be culled from the plant.

Other problematic insects include squash bugs, cucumber beetles, white flies, two-spotted mites, vegetable leaf miners, and cabbage loopers.

Shipping & Packaging
Greenhouse cucumbers for the fresh market are generally shipped in one or two-layer cartons with the fruit individually shrink-wrapped, though this practice is losing favor due to environmental and waste concerns as mentioned above.

There are also other types of packaging (like clamshells for mini cucumbers) related to size, cultivar, and buyer. Newer packaging using recycled and recyclable materials are gaining favor as well. Optimal transit temperature ranges from 50 to 55°F.

References: Colorado State University, New Mexico State University Extension, Ontario Greenhouse Vegetable Growers, Oregon State University, Texas A&M University, University of Alaska Fairbanks Extension, University of California-Davis, University of Florida/IFAS Extension, University of Oregon.

GRADES & GOOD ARRIVAL
There are three classifications for greenhouse cucumbers: U.S. Fancy, U.S. No. 1, and U.S. No. 2.

All three grades require fruit to be at least 11 inches, of proper color and shape, free from decay (anthracnose, bacterial soft spot, black rot, or cottony leak) and serious damage (from bruising, scars, cuts, pulled or shriveled ends, sunken areas, yellowing, freezing injury, or insect damage), as well as clean, fresh, and firm.

The primary difference between the grades is in formation and color: U.S. Fancy requires well-colored and well-formed specimens, U.S. No. 1 fairly well-colored and well-formed, and U.S. No. 2 not badly deformed and fairly well-colored.

Tolerances are for the entire lot or a sampling of at least 25 cucumbers and are as follows: total defects of 10% including 1% decay, and for off-sizing, there should be no more than 5% under specified minimum length and 5% over the specified maximum length.

Canadian good arrival guidelines for greenhouse cucumbers (unless otherwise noted) are broken down into five parts as follows: maximum percentage of defects, maximum percentage of permanent defects, maximum percentage for any single defect, maximum percentage for any single condition defect, and maximum for decay. Canadian destination guidelines are 10-5-5-10-3.

References: DRC, PACA, USDA.


This information is for your personal, noncommercial use only.