Identifying and solving cucumber plant problems

Cucumbers are one of the most-loved vegetable garden crops, trailing closely behind tomatoes and peppers on the favorites list of many gardeners. Cucumbers are easy to plant, delicious, and they’re prolific producers. But even seasoned growers have cucumber plant problems pop up from time to time. In this article, I’ll share some of the more common cucumber growing troubles and introduce some easy organic solutions.

Common cucumber plant problems

Poor planting techniques stunt growth

Cucumbers are easy to grow from seeds sown directly into the garden, but for northern gardeners with short growing seasons, it may help give you a jump on the season to plant transplants out into the garden, rather than seeds. The trouble is that cucumber plants don’t like to have their roots disturbed and commonly suffer from transplant shock. When struggling with this physiological disorder, cucumber transplants show signs of delayed growth and development, negating the timing benefits of planting young seedlings, rather than planting seeds.

To remedy this common cucumber issue, plant seeds directly into the garden rather than transplants. If you live in the north, select a short-season, fast-maturing variety, such as ‘Patio Snacker’ or ‘Straight 8’. If you feel you must plant transplants, try not to disturb the roots at all when planting the seedlings, or start them in plantable peat pots so you don’t have to disturb the roots at all. Also be sure to pamper the seedlings for the first week or two after planting them into the garden. Use a diluted liquid organic fertilizer, cover them with shade cloth for a few days, and make sure they receive adequate water.

Lack of pollination affects fruit set

Sadly, lack of pollination is one of the most common cucumber plant problems these days. If your cucumber fruits (yes, botanically speaking, cucumbers are fruits, not vegetables) are not fully formed or have an end that’s nothing more than a tiny nub, poor pollination is likely to blame. Each flower must be visited by a pollinator many, many times in order for the fruit to fully form. The more pollinators you have around, the better.

Do not use pesticides in the vegetable garden; even certain organic pesticides can affect bees. Increase the number of pollinating insects in your garden by inter-planting your edible crops with lots of flowering herbs and annuals, such as sunflowers, oregano, basil, zinnias, dill, and black-eyed Susans.

Lack of water limits cucumber vine growth

Cucumber vines are thirsty, and they’ll let you know if they don’t receive ample irrigation water. If your vines wilt or are growing more slowly than you’d like, lack of sufficient water could be to blame. Like all plants, cucumbers grown in the ground prefer to receive a deep, penetrating soaking of their root zone once or twice a week, rather than light, shallow irrigation every day.

Cukes grown in the ground should be mulched with a layer of shredded leaves or straw to stabilize soil moisture. Container-grown cukes, will need to be deeply watered every day during hot summer weather. Do not do “splash and dash” irrigation that barely gets the leaves and soil wet. Target the hose right onto the soil and allow it to run through the soil and out the drainage hole in the bottom of the pot.

Poor nutrition affects cucumber plant health

Cucumber vines are heavy feeders. If your vines are pale green or yellow, especially the older leaves, they may need a nutritional boost. In the garden, adding a few inches of compost in the spring should provide all the nutrition your vines need. But, if you find them yellowing as the summer progresses, feed the plants with a liquid organic fertilizer once a month. You can also work organic granular fertilizer into the planting beds prior to planting the seeds but only if a soil test tells you its necessary. Too much nitrogen yields long, green vines with few flowers or fruits.

Container-grown cucumbers will need to be regularly fed with a liquid organic fertilizer. Be sure to use a high quality potting soil when planting them. Here’s the recipe I use for making my own potting soil.

Powdery mildew limits cucumber growth

If the leaves of your cucumber plants appear to be dusted in talcum powder, powdery mildew is the cause. This is one of the most common cucumber plant problems gardeners deal with. Thankfully, it’s more of an aesthetic issue, though heavy mildew limits photosynthesis and growth. There are many different species of this fungal organism that live on the leaf surface.

Plant cucumber varieties with a known resistance (the disease resistance-code PM will be found on the seed packet or in the seed catalog description), such as ‘Eureka’, ‘Jackson’, and ‘Transamerica’. Do your best to keep the foliage dry when watering your garden. Most fungal diseases thrive on wet foliage. Water in the morning to give the plants plenty of time to dry before nightfall. Powdery mildew on cucumbers is managed with organic fungicides based on Bacillus subtilis (Serenade™) or bicarbonates (including Green Cure™ and Bi-Carb®).

Cucumber beetles are one of the most difficult cucumber growing problems

Depending on where you live, you have one of two different species of cucumber beetles hanging about your garden: the striped cucumber beetle and the spotted cucumber beetle. Both species feed on all members of the cucurbit family. The adult beetles make ragged holes in the leaves and flowers, while the larvae feed on plant roots.

Your first line of defense is to plant beetle-resistant varieties. Since they’re attracted to a particular compound found in the leaves of cucumber plants, varieties with low levels of these compounds are best. ‘Saladin’ and ‘Gemini’ are two great cucumber beetle-resistant varieties. Cover the plants with floating row cover from the time the seeds germinate until the plants come into flower to keep the beetles at bay.

You’ll also have great success trapping the beetles by placing yellow sticky cards just above the plant tops. For large cucumber plantings in rows, run a strip of yellow caution tape coated in a non-drying glue, such as TangleTrap, on stakes just above the plant tops. Sadly, you may accidentally trap some “good bugs” with this technique, too, but pest insects are more attracted to yellow than most pollinators are. Cucumber beetles love Blue Hubbard squash, so plant a few vines of this winter squash to lure the beetles away from your cukes.

Surprisingly, cucumber beetles are also great pollinators of cucumber plants, so most of the time I let them be. They seldom cause significant damage to the plants from their feeding activities — unfortunately, however, cucumber beetles transmit deadly bacterial wilt, which brings us to one of the biggest cucumber plant problems of all….

Bacterial wilt kills cucumber plants

This pathogen affects all members of the cucumber family, including cukes, muskmelons, pumpkins, and squash. The first sign of infection is wilted and drying leaves, sometimes seemingly overnight. It’s extremely disheartening to have healthy, prolific vines one day and then wilted and dead vines a few short days later.

An easy to way to confirm that bacterial wilt is the cucumber issue you’re dealing with, is to cut a wilted stem off at the base and touch the cut with your fingertip. If white, thin, thread-like strands come out of the cut when you pull your finger slowly away, your plants have bacterial wilt. Spread by the feeding activity of cucumber beetles, there is no cure for this cucumber plant disease. Destroy the plant immediately to keep it from spreading to other cucumber vines.

While you may think that wiping out every cucumber beetle within three miles of your garden is the way to combat this pathogen, that isn’t the best solution, even if it was possible. Instead, focus on planting only bacterial wilt-resistant cucumber varieties in your garden in future years. You know what they say: An ounce of prevention is worth a pound of cucumbers! Some of my favorite bacterial wilt-resistant cucumber varieties are ‘County Fair’, ‘Salad Bush’, ‘Marketmore 76’, and ‘Saladin’. They’re all great tasting and very prolific, in addition to resisting wilt.

Fusarium wilt on cucumbers

Another one of those cucumber plant problems that’s a challenge to diagnose and defeat is fusarium wilt. This pathogen tends to be far more common in warm, southern climates and can affect a broad diversity of vegetable plants in addition to cucumbers. Early signs include drooping leaf stems. Sometimes an entire branch might wilt, starting with the lower portion and progressing upwards. Slice open the main stem of a cucumber plant you suspect is infected with fusarium wilt. If it’s infected, there are dark streaks running lengthwise through the stem. Sometimes there are dark, sunken cankers at the base of the vine, too.

This pathogen lives in the soil for many years and spreads from plant to plant on water, equipment, or plant debris. Even humans can accidentally spread fusarium wilt. Sadly, there is no cure. Remove and destroy infected plants immediately.

Focus on preventing it next year by planting only resistant varieties with the disease-resistance code FW on their seed packet. Soil solarization can help kill the spores in the top few inches of soil. Rotate your cucumber crop to a new place each year. Biological fungicidal soil drenches and additives can help, too, including those based on the bacteria Streptomyces griseoviridis (brand name MycoStop®) or a granular one based on the fungus Trichoderma virens (brand name Soil Guard®).

Cucumber mosaic virus is a common cucumber problem

This deadly plant virus is spread from plant to plant on tools and hands. It also spreads through the feeding of sap-sucking aphids. Symptoms of cucumber mosaic virus most often appear as a mosaic-like pattern of light and dark green on the leaves (almost like a checkerboard). The growing points are malformed, and there are spots, warts, or line patterns on the fruits. Unfortunately, there is no cure for this plant virus. Prevention is key.

Only purchase cucumber varieties with a resistance to this virus. This is especially important if you’ve had trouble with this pathogen before. The disease resistance-code CMV will be on the seed packet or seed catalog description of resistant varieties. Good choices include ‘Boston Pickling Improved’, ‘Eureka’, ‘Little Leaf’, ‘Salad Bush’, ‘Straight Eight’, and ‘Marketmore 76’. Purchase new, certified virus-free seeds each season. Though “cucumber” is in the name of this pathogen, it affects a wide range of plants, including vegetables, flowers, and weeds. Destroy infected plants to prevent further spread.

Cucumber plant problems solved

It may seem daunting to identify and manage issues with your cucumber vines. But the truth is that you’ll have many more years of success than you’ll have troubles. With healthy soil, adequate water and nutrition, and proper care, healthy and productive cucumber vines are definitely in the cards. Enjoy the harvest!

For more on managing garden diseases and pests, check out the following articles:

Zucchini problems and how to solve them
Common tomato diseases
Plant pathogens and organic controls
6 steps to grow a healthy tomato garden
Guide to vegetable pests with organic fixes

Have you faced cucumber plant problems in the past? Tell us your issues and solutions in the comment section below.