Cucumbers (Cucumis sativus) are a vegetable garden staple. These vining plants are in the gourd family (Cucurbitaceae) and include not only cucumber, but squash, pumpkin, gourd, watermelon, and cantaloupe. This member of the "vine crops" grows on long trailing vines that can take up quite a bit of space in the home vegetable garden, so plan accordingly if you are thinking of adding them to your home garden. Cucumbers can be successfully grown on trellis systems to save space and make harvest easier.
Cucumbers perform best in fertile, well-drained soils in full sun. If a soil test has yet to be conducted, apply and incorporate 1 to 2 pounds of all-purpose garden fertilizer, such as 10-10-10, per 100 square feet prior to planting.
Cucumbers are a warm-season crop. Plant cucumbers after the danger of frost is past and soil temperatures have warmed to 60 to 70°F. In central Iowa, cucumbers may be planted in mid-May. Gardeners in southern Iowa can plant one week earlier. Plant 1 week later in northern portions of the state. The last practical date to sow cucumbers is July 10.
Cucumbers are normally planted in "hills." Plant 4 to 5 seeds per hill at a depth of 1 inch. Later, remove all but 2 or 3 plants per hill when seedlings have 1 or 2 true leaves.
For an earlier crop, cucumbers can be started indoors. Start seeds indoors 2 to 3 weeks before the anticipated outdoor planting date. Peat pots, Jiffy 7's, and other plantable containers work best as both plant and container are transplanted into the garden, resulting in little damage to the plant s root system. Sow 3 to 4 seeds per container. Later, remove all but two seedlings. Transplant outdoors when plants have 1 or 2 true leaves. Prior to planting, harden the plants outdoors for a few days in a protected location to lessen transplant stress.
Hills of cucumbers should be spaced 3 to 5 feet apart within the row. Rows should be 4 to 5 feet apart. For bush varieties, a three-foot spacing between hills and rows should be adequate.
Cucumbers can also be grown in rows. Sow seeds 6 inches apart. After germination, thin the seedlings so the remaining plants are spaced 15 to 18 inches apart.
Cucumbers and other vine crops are monoecious. Monoecious plants have separate male and female flowers on the same plant. Male and female flowers are similar in appearance. However, the female flowers have small, immature fruits at their base. Pollen is transferred from the male to the female flowers by bees. When properly pollinated and fertilized, the female flowers develop into fruit. The first flowers to appear on cucumbers and other vine crops are male. Female flowers appear shortly after that.
Gynoecious varieties are special hybrids that produce predominantly female flowers. Seeds of a standard monoecious variety are commonly included in the seed packet to ensure adequate pollination. (The seeds of the monoecious variety may be dyed or placed in a separate packet.) Gynoecious varieties often outproduce standard varieties when a pollenizer (monoecious variety) is present.
There are also parthenocarpic cucumber varieties. These varieties develop fruit without pollination. As a result, the non-fertilized fruit does not contain seeds. Parthenocarpic varieties must be isolated from standard varieties to prevent cross-pollination and seed development.
Cucumbers will not cross-pollinate with squashes, pumpkins, muskmelons, or watermelons. Cucumber varieties may cross with one another. However, the quality of this year s crop is not affected. (An exception is the cross-pollination of parthenocarpic varieties with standard varieties.)
Several different types of cucumbers are available to home gardeners. Slicing cucumbers are generally long and cylindrical with dark green skins. Pickling cucumbers are short and blocky. "Burpless" varieties produce mild-flavored fruit. For individuals with small gardens, compact or bush varieties are available.
- Corinto - very dark green, small seed cavity
- Thunder - very early.
- Fanfare - semi-bush, monoecious, 1994 All-America Selection.
- Marketmore 76 - uniform, dark green fruit.
- County Fair - nearly seedless if isolated from other cucumbers.
- Calypso - gynoecious, early to mid-season.
- Fancipak M - gynoecious, early to mid-season.
- Diva - gynoecious, parthenocarpic, 2002 All-America Selection.
- Sweet Slice - monoecious, slicing.
- Tasty Green - monoecious, slicing.
- Salad Bush - 1988 All-America Selection, slicing.
- Spacemaster - slicing.
- Bush Pickle - pickling.
- Katrina - thin skin, seedless, very heat tolerant
- Picolino - gynoecious, parthenocarpic, thin dark green skin
- Lemon - similar in size and appearance to a lemon, light yellow skin, white flesh.
- White Wonder - cylindrical fruits with ivory-white skin.
Control weeds with frequent, shallow cultivation and hand pulling until the vines cover the ground. Water plants once a week during dry weather. Prevent cucumber beetles from damaging young plants by covering them with floating row covers or other protective materials or by using insecticides. (Remove the protective coverings when flowering begins.) Cucumber plantings made after mid-June are less likely to be damaged by cucumber beetles because of the smaller population of adult beetles.
Bitterness in cucumbers is caused by the compounds cucurbitacin B and cucurbitacin C. The cucurbitacins are normally found in the cucumber plant's leaves, stems, and roots. The cucurbitacins spread from the vegetative parts of the plant into the cucumber fruit when the plants are under stress. Hot, dry conditions are usually responsible for bitterness in cucumbers in Iowa.
Bitterness does not accumulate uniformly in the cucumber fruit. The cucurbitacins are usually concentrated at the fruit's stem end and just under the skin of the cucumber. Bitter cucumbers can sometimes be salvaged by cutting off the stem end and peeling the remainder of the fruit.
Cucumber varieties differ in their tendency to be bitter. Varieties that usually experience few problems with bitter fruit include Sweet Slice, Sweet Success, and Marketmore 76.
Watering cucumber plants once a week during hot, dry weather may also be helpful.
Poor Fruit Set
There are several reasons why cucumbers may not be setting fruit, including poor pollination and being too early in the season. Learn more about why cucumbers and other vine crops do not set fruit in this article: Reasons for Poor Fruiting of Vine Crops.
Poorly-shaped fruit are usually the result of poor pollination. Poor pollination may be due to cool, wet weather and improperly applied insecticides that limit bee activity. When insecticides are necessary, select an insecticide with low toxicity to bees and apply it early in the morning or late in the evening to reduce the risk to bees.
Cucurbit Bacterial Wilt
Bacterial wilt occurs primarily on cucumbers and melons but also may be a problem on squash and pumpkins. The disease is caused by the bacterium Erwinia tracheiphila. Typically the leaves turn a dull green color, and a progressive wilting of lateral leaves occurs. The pathogen moves through the main stem, plugging the vascular tissue, and eventually causes wilting and death of entire plants.
Learn more about identifying and treating this disease in this article: Cucurbit Bacterial Wilt.
The striped cucumber beetle is a common pest of cucurbit crops in the Midwest. The spotted cucumber beetle, also known as the southern corn rootworm, is also a pest of cucurbit crops, but the striped cucumber beetle has more economic impact due to its ability to transmit bacterial wilt.
Early in the season, feeding by larvae can stunt and even kill seedlings and small transplants. Adult beetles feed mostly on leaves but will feed on stems if populations become too high. Once plants have established and begin to mature, they can survive high levels of defoliation, but this still isn’t acceptable due to the transmission of bacterial wilt through feeding. At high populations, beetles can cause cosmetic damage to fruits.
Covering plants with row cover or frost fabric can prevent young plants from being eaten or damaged by cucumber beetles. The covering must be removed when plants start to flower to allow for proper pollination.
Learn more about cucumber beetle in this article from the University of Minnesota: Cucumber Beetles in Home Gardens.
Anthracnose is caused by the fungus Colletotrichum orbiculare and can be destructive of cucurbits during warm and moist seasons. This disease causes lesions that look water-soaked to yellow, circular spots, and eventually dark brown or black irregularly shaped spots. Lesions can develop in all above-ground parts (leaves, petioles, stems, and fruits).
Learn more about Cucurbit Anthraconse in this article: Cucurbit Anthracnose.
Other Diseases & Insects
Many of the diseases common to any of the vine crops can be problematic for cucumber. Those issues listed below are common on other cucurbits (like pumpkin, squash, or melon) but only occur occasionally or rarely on cucumber.
Harvest cucumbers frequently (every 2 to 3 days) as the fruit develops quickly and can easily grow beyond the desired size. Pickling varieties should be harvested when the fruits are 2 to 4 inches long. Slicing cucumbers should be 6 to 8 inches long and 1 1/2 to 2 inches in diameter but still dark green and firm. Over-mature cucumbers left on the vine inhibit additional fruit set.
Cucumbers can be stored for 10 to 14 days at 50 to 55°F and 90 to 95% relative humidity.
- When can I plant cucumbers in the garden?
- How do gynoecious cucumber varieties differ from other varieties?
- My cucumber plants are blooming heavily, but aren't producing many fruit. Why?
- Why are some of my cucumbers bitter?
- Why are some of my cucumbers misshapen?
- Will cucumbers cross-pollinate with other vine crops?
- When should I harvest cucumbers?
- Harvesting and Storing Vine Crops
- Vegetable Harvest Guide
- Vegetable Planting and Harvesting Times
- Planting and Harvesting Times for Garden Vegetables (publication)
- Suggested Vegetable Varieties for the Home Garden (publication)
- Cross-Pollination Between Vine Crops
- Crop Rotation in the Vegetable Garden
- Small Plot Vegetable Gardening (publication)
- Container Vegetable Gardening (publication)