15 Common Problems With Garden Cucumber Plants
Are your garden grown cucumbers running into some problems this season? Although they are hardy vining vegetables, cucumbers can run into several common issues. In this article, gardening expert and former organic farmer Logan Hailey walks through the most common problems you'll likely run into when growing cucumbers this season.
Cucumbers are tender annuals that absolutely love the warmth and sunshine. You can plant cucumbers once and enjoy their continuous production all season long. These eager plants can yield in great abundance as they climb a trellis or ramble around your garden beds.
But– like all of us– cucumbers aren’t always easygoing. They can be finicky about water, pruning, and pollination. They also are susceptible to a range of pests and diseases that commonly afflict the Cucurbit family (cukes, zukes, squash, melons, and the like).
If you’re struggling with your cucumber plants, there are lots of easy fixes to help them bounce back. The key is to properly diagnose the problem and take action ASAP. Let’s dig into everything you need to know about the 15 most common cucumber problems and what to do about them.
Common Problems & Prevention
You’re not alone with your sad or failing cucumber plants. Every gardener and farmer has had their fair share of problems with this classic salad-topper.
Although cucumber plants can be crazy vigorous, they are notorious for throwing a fit in cold weather, excessively humid conditions, or pest and disease attacks. Fortunately, they can also bounce back really quickly!
Use this simple guide to identify what may be affecting your cucumbers and figure out how to heal them.
Seeds Never Germinate
You’ve excitedly sown your cucumbers and earnestly watered them, only to notice a few weeks later that nothing has happened! Failed cucumber germination is a common issue for beginner and advanced gardeners alike.
It can set back your planting dates and feel like a waste of soil and time. Plus, specialty varieties of cucumber seeds can be expensive to re-order.
If your cucumber seeds don’t come up, you may have a problem with:
Cucumbers are a favorite for seeding with children because they are fairly large and easy to handle. However, it is a common misconception that you can toss these seeds aimlessly into the soil and still see them come up.
Cucumber seeds need to be planted about ½” to 1” deep. If they are too deep, the seed won’t have enough endosperm (storage “food”) to sustain it as it grows toward the surface. If they are too shallow, the seeds may float to the surface of the soil when watered and get exposed to the drying sunlight. As a rule of thumb, most seeds need to be planted about twice as deep as the seed dimensions.
Cucumber seeds are very popular with voles and mice. If you notice that your cukes aren’t coming up, check around the seeding area to see if there are any holes left behind where rodents may have dug them up.
The easiest trick to keep nursery rodents off your cucumbers is simply using a tarp. Seed your cukes, then cover them with a tarp for 3-5 days. Set peanut butter mouse traps on top of the tarp. When the seeds begin germinating, pull off the tarp. You can also use hardware cloth to build a protective cage around the seed trays. You can also adopt a garden cat, which many gardeners prefer.
Swampy or soggy soil is a bad idea for any vegetable, but especially cucumbers. Overwatering can lead to damping off issues (described below) and failed germination. On the flip side, if the soil dries out, your seeds may never emerge.
Check the seedling soil on a daily basis to ensure that it has an even amount of moisture. When the top few inches of soil start to dry, water thoroughly until water comes out of the bottom drainage hole, then stop. If direct seeding the garden, you may want to cover it with a row fabric to conserve water as you wait for seeds to emerge.
Most seeds are only viable for a few years. Old seeds can germinate erratically, unevenly, or not at all. Cucumber seeds can last for up to 6 under the right conditions (cool, dark, and dry storage), but you are more likely to enjoy the highest germination rates with the newest seeds possible.
Cucumbers are tender annuals that won’t germinate in soils below 50-60°F. The seeds really don’t like the cold and may germinate super slowly or not at all. If direct seeding in the garden, use a soil temperature probe to be sure that the soil is at least 70°F. Alternatively, add a heating mat set at 80°F beneath your seed starting trays.
Addressing failed germination is all about fixing the seeding environment. Whether you’re direct sowing or starting cucumbers indoors, the basic requirements for seed starting success are the same.
Seedlings Rot at the Base
You may notice that those fleshy cucumber seeds did in fact germinate, but now they seem to be rotting at the base. While it may appear that those oversized cotyledon leaves weighed them down, a closer examination usually reveals that they’ve been girdled right where they emerge from the soil. The bottom of their stems may look white, brownish, and skinnier than the rest of the stems.
Cucumbers are members of the Cucurbitaceae family, which also includes zucchini, winter squash, pumpkins, melons, and gourds. All of these plants are known for their susceptibility to a seedling disease called damping off. This annoying disease is caused by a variety of fungal pathogens, including Pythium, Rhizoctonia, and Fusarium. They thrive in excessively moist, humid conditions with low airflow.
If your cucumber seedlings fall victim to damping off, it is a sure sign that there is something wrong with your seed-starting area. While you can’t save the affected baby plants, you still have time to improve the environment and re-seed.
To Prevent Dampening Off:
- Maintain adequate airflow.
- Add a fan or open a breezy window in your seed-starting area.
- Avoid over-watering cucumber seeds.
- Ensure very well-drained soil (add perlite, vermiculite, compost, or peat moss).
- Sanitize your tools and pots.
Fortunately, only baby cucumber seedlings are susceptible to damping off. Once your plants have gotten past the seedling phase, you no longer have to worry about this disease.
Wilted, Sad Transplants
The Cucurbit family is also notorious for how much they loathe transplanting. If the delicate cucumber taproot is disturbed during planting, you may notice symptoms of transplant shock such as:
- Excessive wilting of the whole plant (no matter how much water is present).
- Yellowing or white, pale leaves.
- Fallen over seedlings.
- Very “sad” looking plants.
Preventing transplant shock simply requires a little extra TLC for your baby cucumber plants. Though they grow very quickly once established, these seedlings aren’t nearly as resilient as tomatoes or other veggies.
For Happy Transplants…
- Ensure loamy, well-drained soil with plenty of organic matter.
- Make a hole that is 2 times as wide and deep as the seedling.
- Be gentle when removing cucumber seedlings from their pots.
- Don’t transplant too early or too late!
- The roots of the seedling should be established and holding onto the soil.
- This usually takes 2-4 weeks from the time of seeding.
- Water in transplants with a diluted kelp solution to help reduce transplant shock.
- Transplant during the evening.
- Cover with row fabric to insulate from temperature fluctuations.
Helping cucumber transplants recover from transplants is a little more difficult than preventing it in the first place. Your best bet is to protect the damaged plant with a row cover and watering with a diluted kelp solution to help it bounce back. If the shock is really bad, you may need to replant or sow the seeds directly in the garden to avoid transplanting issues.
Weak or Slow Vine Growth
Low vigor is typically a sign of an unhappy cucumber plant. If it seems like your plants are taking forever to “take off” and get growing, you may be facing some of these issues:
Once your cucumbers are already in the ground, the easiest way to improve their vigor is by checking the soil, fertility, and moisture levels.
Like most veggies and fruits, cucumbers really don’t like compacted, heavy soil. It basically feels like their roots are trying to press into concrete. Be sure that you have thoroughly loosened the lower soil profiles with a broadfork or digging fork. Incorporate compost or other organic matter to help improve drainage.
Once plants are already in the ground, it can be difficult to fix the soil. However, you can gently loosen the area around the plant with a hoe or mulch with vermicompost to encourage worms to do the soil-loosening work for you.
Cucumbers are moderate to heavy feeders that need a nice “boost” to take off. Weak, flimsy vines and yellowing leaves can be a sign of nitrogen or potassium deficiency. Add an all-purpose slow-release fertilizer or a diluted fish fertilizer to give plants a boost.
Lack of Water
Cukes are thirsty crops and struggle under drought conditions. Install drip lines or soaker hoses to ensure that they are getting plenty of moisture. Add straw or dried leaf mulch around the base to conserve water in the soil. Water as deeply as possible (without allowing water to pool up) and keep the soil consistently moist.
You will also want to address any potential pest issues (described below) that could be robbing the young plant of its much-needed photosynthetic energy.
Pale Yellowing Leaves
When cucumber leaves turn pale, they are trying to tell you that something isn’t right. The chlorophyll in plant leaves is what gives them a vibrant green color. It allows them to make their own food via photosynthesis. When cucumber leaves are no longer green, they can’t photosynthesize as effectively and may not be able to yield their juicy fruits.
Once you’ve ruled out transplant shock in young seedlings, the most common reasons for pale or yellowing leaves are watering issues, nutrient deficiencies, or a lack of sunlight.
Remember that cucumbers need consistent, even moisture. The soil should never be bone dry nor overly soggy.
Cukes also need plenty of fertilizer. Remember to amend with an all-purpose organic fertilizer or compost at the time of planting.
Lastly, recall that cucumbers need full sunlight to thrive. If they are growing in the shade of another plant or a building, they may be struggling to maintain their vibrant green leaf color and instead turn pale, grey, or even white. Plant cukes in an area with at least 6-8 hours of direct sun per day.
Tiny Holes in Leaves
Flea beetles are tiny black hopping bugs that can attack many of our favorite garden crops. They are less than ⅛ inch long and have metallic-colored bodies. On cucumbers, their feeding pattern looks like a million tiny holes in the leaves.
These holes often get a yellow or brown ring around them as the leaf tissue begins to decay. The damage is most severe in the spring.
Get rid of flea beetles ASAP with a homemade neem spray or horticultural oil. Yellow sticky traps are the easiest way to monitor flea beetle populations. Hang them on your cucumber trellis or nearby cucumber beds.
You can also plant cucumber companion plants to attract beneficial predators like parasitic wasps and lacewings. Alternatively, order lacewing larvae from a biocontrol company and release them into your garden.
If you have flea beetles on your cukes, chances are that you may be dealing with an infestation in other parts of your garden. Be sure to check your squash, melons, and brassicas for damage.
As a means of prevention, I always cover newly transplanted crops with a light row cover to physically exclude pests like flea beetles while they get established.
Cucumber Beetles Everywhere!
If you love growing cucumbers, these striped or spotted yellow-and-black beetles can become the bane of your existence! They show up and populate very quickly, feeding on cucumber leaves, flowers, and fruit. Cucumber beetles can seriously reduce yields, damage your cukes, and spread harmful diseases like bacterial wilt and cucumber mosaic virus.
Identifying Cucumber Beetles
- About ¼ inch long.
- Yellow and black striped or spotted backs.
- Dark heads with long antennae.
- Worm-like white larvae with 3 pairs of legs.
- Ragged holes eaten in foliage and flowers.
- Feeding scars on fruit.
Getting rid of cucumber beetles is similar to eradicating flea beetles. You can use neem oil, horticultural oil, and yellow sticky traps. You can also knock them on the ground and vacuum them up with a hand-held vacuum. And don’t forget those companion plants, beneficial predators, and row covers!
Like flea beetles, cucumber beetles can attack the entire Cucurbit family, including your squash and zucchini. Check all your plantings and take preventative measures when necessary.
All Flowers, No Fruit
While the yellow flowers of cucumbers are a pretty site, we’re obviously growing them for the hydrating, juicy fruits. Cucumber flowers can appear early in the season, depending on your hardiness zone. If you’re noticing your plant only producing blossoms, you may have a pollination issue.
Lack of pollination looks like:
- Fallen flowers with no fruit.
- Deformed cucumbers.
- Abnormally small cucumbers.
- Super slow growing fruit.
Like their squash cousins, cucumbers need bees and other pollinators to help them transport male pollen to female flowers that ultimately produce fruit. Because cucumber plants are monoecious (both male and female blooms on the same plant) you don’t need another plant to aid in this process. However, you do need insects to help get the job done.
Plant lots of pollinator-attracting companion plants to bring bees into your garden! Our favorites include phacelia, white alyssum, yarrow, and marigolds.
You can also hand pollinate cucumbers if your garden doesn’t get the pollinators that it needs. They can also be cross pollinated by hand as well. If you’re really lacking in pollinator activity in the garden, you may want to plant a parthenocarpic or “self-pollinating” cucumber variety that doesn’t require bee pollination to fruit.
Powdery Appearance on Leaves
If it looks like your cucumber leaves have been dusted with white or grey flour, it’s most likely a sign of powdery mildew. Hot days and humid nights are catalysts for this dreadful disease. The fungus Podosphaera xanthii is the most common culprit and it also loves all the cucurbit cousins.
Powdery mildew symptoms include:
- Dusty gray leaves.
- White blotches.
- Fuzzy mildew appearance on stems.
- Yellowing or browning leaves.
- Rapidly spreading mildew dust to nearby plants.
Make a homemade baking soda spray of 1 tablespoon baking soda, 1 tablespoon vegetable oil, and 1 teaspoon natural dish soap mixed with 1 gallon of water. Spray directly on affected leaves. You can also make a vinegar spray with 2 to 3 tablespoons of vinegar in 1 gallon of water. Only apply this one in the evening to ensure it doesn’t burn your plants.
Lastly, neem oil is a natural fungicide that has the added benefit of repelling pests. Follow dilution instructions and spray once a week until symptoms subside.
In the future, source PM-resistant cucumber varieties like ‘Indy’, ‘Thunder’, or ‘Alibi’.
Rotten Fruit on the Ground
When cucumbers are allowed to vine along the soil, they have a tendency to get unruly. You may flip over some tangled vines and discover that your precious cuke fruits have started rotting in the dirt. Excessive rainfall or irrigation can exacerbate this problem. Rodents and fungi may also be attacking the fruit.
The easiest way to avoid rotten fruit is to never let it touch the ground! You can apply a mulch of dry straw or chipped leaves so the fruits can rest on a dry surface. Or you can trellis your cucumbers upward so that the fruit dangle in the air! I like to do both for maximum benefits. As a bonus, the cucumber skins will be cleaner and more edible right off the vine.
My favorite cucumber trellis can be made by simply pounding two pieces of 6-foot rebar into the ground and then using zip ties to hang a cattle panel across them. Alternatively, trellis cucumbers up a fence, archway, greenhouse string, or an A-frame trellis.
Vines Overgrowing Garden Beds
Cucumbers can be quite unruly when they have the soil, moisture, and fertility they need. But sometimes that means their vines start rambling over other plants or escaping your garden beds. This makes it difficult to weed and harvest from the patch.
Trellis, trellis, trellis! Keep your garden neater and easier to tend by trellising your cukes with one of the ideas above. Pruning will also ensure that the vines don’t get overly tangled or out of control.
Lots of Stems and Leaves, Little Fruit
Cucumbers have a tendency to put out large amounts of “suckers” or lateral shoots with extra stems and leaves. These side stems “suck” away energy from the main vine and lead to lower yields and smaller cucumbers.
While tomato pruning is a well-known practice, most gardeners don’t realize that their cucumbers can benefit from pruning as well. On commercial production organic farms, I have always found that the highest yielding cucumber crops come from plants that are pruned.
And if you think that snipping off a few vines seems won’t make a difference, consider that pruned cucumbers can yield up to 2-3 times more cuke fruits than their unpruned counterparts! That’s because pruning encourages the plant to put more energy into fruit production rather than foliage growth.
You can identify the cucumber suckers by finding lateral shoots that come off of the main vine stem. Just like tomato suckers, these shoots will have extra growing tips at their end as they try to branch off and grow whole new vines. Use clean pruners to cut them off at their base and let the main vine continue channeling its energy into fruit.
I like to prune cucumber suckers once per week to stay on top of their growth. Trellised cucumbers are much easier to prune. As a bonus, your garden will look tidier and loaded with fruits!
Target-Shaped Spots on Leaves
Windy, wet weather is never good news for cucumber plants. If you notice leaf spots with a target-like ring around them, an angular leaf spot is the most likely culprit. Caused by the bacteria Pseudomonas syringae, this disease leads to a variety of symptoms like:
- Rounded or angular cream spots.
- Yellow halo around the spots.
- Center of leaf spots may dry and drop out (giving the ‘target” appearance).
- Spots are bound by leaf veins.
- Leaves dry and fall prematurely.
- Stick drops of white liquid on underside of wet leaves.
Cultural control is the most important means of preventing angular leaf spots. Always use drip irrigation and avoid overhead watering at all costs. Remove affected leaves as soon as possible and burn crop residues at the end of the season.
Practice crop rotation and keep the garden as weed-free as possible. Don’t work on cucumbers when they are wet (you may accidentally spread the disease). Source certified disease-free seeds of varieties that are resistant to angular leaf spot, including ‘Citadel’, ‘Bristol’, and ‘Little Leaf’.
Vines Suddenly Wilt
If your cucumber vines suddenly start wilting during the day but recover overnight, you may be dealing with a nasty bacterial disease called bacterial wilt. In spite of ample soil moisture, infected plants will show these symptoms:
Bacterial Wilt Symptoms
- Dull green leaves.
- Wilt during the day and recover at night.
- Yellow and brown leaf margins.
- Dying leaves.
- Rapid spread and loss of crop.
- Progressive wilting down the vine.
- Lots of spotted or striped cucumber beetles are present.
Unfortunately, cucumber plants have no cure for bacterial wilt. Remove the infected plants immediately to prevent them from spreading.
Next season, plant BW-resistant varieties such as ‘County Fair’, ‘Little Leaf-19’, or ‘Cross Country’. Also take extra care to control cucumber beetles, as these are often the primary vectors for spreading bacterial wilt.
Shriveled Brown or Black Foliage
We all know how much cucumbers love the heat and despise the cold, but it doesn’t necessarily have to frost to make these tender annuals unhappy. If you notice shriveled blackened leaves after a cold night, your cukes may be suffering from cold damage. In milder cases, some parts of the plant may just appear wilted.
If the weather forecast predicts temperatures below 55°F, consider protecting your cucumbers with a row cover or a frost blanket. Cold damage is most common in the spring when planting young cucumbers in the garden. As an added layer of protection, you may opt to wait a few extra weeks until the weather has thoroughly settled.
Cucumbers aren’t as easy going as their zucchini cousins. They also aren’t as finicky as carrots and cauliflower. Nonetheless, these plants can be really rewarding to grow if you understand their needs in advance. Establishing robust plants from the beginning is the key to preventing problems in your cucumber patch.
- Plant cucumbers in well-drained loamy soil.
- Irrigate with drip lines or soaker hoses to avoid wetting the leaves.
- Be very careful when transplanting so you don’t disturb the roots.
- Use row cover to help newly planted seedlings get established.
- Amend with compost or an all-purpose organic fertilizer.
- Regularly scout for pests.
- Companion plant to attract beneficial predators.
- Practice good garden sanitation to keep diseases at bay.
Now that you know how to keep most of the common problems away, it’s time to act on that. Remember, prevention is always easier than treatment when it comes to cucumbers, or any garden grown veggie!