How to Grow Series

Cucumbers - Troubleshooting

Why are my cucumbers bitter?

Most cucumbers contain cucurbitacins that cause cucumbers to taste bitter. This bitterness can be more pronounced when the plant is under stress. For example, some cucumbers can become quite bitter during bouts of drought and very high temperatures. The bitterness is usually concentrated at the end of the cucumber where the stem grows, so cutting off an inch or two of the cucumber can remove most of the bitterness and salvage the cucumber. To help reduce bitterness, make sure your plant receives regular watering each week. Mulch well to prevent the soil from getting too dry or too hot between watering. Make sure your plants get enough fertilizer and are not stressed from disease or pests such as the cucumber beetle. You can also grow varieties that do not contain this bitterness gene or that contain other genes that fight the bitterness.

Why do I have flowers, but no cucumbers?

Male flowers will form on your plants first and drop off before female flowers begin to form. Female flowers will have a swollen section at the base of the flower that may look like a miniature cucumber. This is the flower that will form the cucumber once it is pollinated by the male flower. If you have lots of female flowers and male flowers but fruit is still not growing, you may not have enough bees to pollinate your plants. You can hand pollinate if necessary. Just pop off one of the male flowers and touch the anther of the male flower to the stigma of the female flower. These are in the middle of each flower. You can also use a small paint brush to transfer the pollen from the male flower to the female flower. Prevent using broad spectrum pesticides that kill the bees as well as harmful pests to help prevent this problem in the future.

What is eating my cucumber plants?

Cucumber beetles are a likely culprit. They come in spotted, striped and banded varieties and not only harm cucumbers but squash, melons, gourds and pumpkins as well. The adults will eat the leaves, stems and even the fruit while the larvae will eat the roots of a plant. Controlling them can be a challenge, but it can be done.

What is eating my cucumber plants?
spotted cucumber beetle Diabrotica undecimpunctata howardi Adult(s)
Photo by Gerald Holmes

Start by not using broad spectrum pesticides in your yard. Though you may kill the beetles initially, you will also kill their predators as well making future problems even worse.

Start by hand-picking as many of the beetles as you can and dunking them in soapy water to kill them. I have heard some people even use a shop vac to vacuum up the beetles since they don't like touching them with their hands. Just make sure the suction isn't too strong to take the plant with it. Check at the base of plants looking for eggs. Use a spoon to remove the eggs and dunk them in soapy water. Stir up the soil around the plants, careful not to disturb the roots too much and leave the soil exposed to the elements a couple of days, then mulch heavily with straw.

What is eating my cucumber plants?
striped cucumber beetle Acalymma vittatum Adult(s)
Photo by Gerald Holmes

Protect plants from the beetles by installing row covers at planting time and hand pollinating the flowers if necessary if the row covers need to stay on longer than normal. Some people have success setting out their cucumber plants later than normal to avoid the first generation of the beetle. Some people also have success in setting out their plants early, protecting them from frost, that way they are larger plants when the beetles start to arrive.


If cucumber beetles were a problem the year before, make sure you remove any leaf litter or tall grasses around your garden area in the fall where beetles can over winter. Plant cucumbers in a different area of the garden rotating your crops on a yearly basis to confuse the pest. You can also purchase parasitic nematodes and apply them to the soil which will attack the larvae to help reduce numbers the following year.

For more information on pests that can bother cucumber plants, check out this excellent resource:

Leaves have white powdery marks on them.

The white powdery marks on cucumber leaves is most likely powdery mildew. This occurs later in the season when humidity is very high and air circulation is low. Powdery mildew does not normally kill a plant, but the mildew can spread from leaf to leaf making the plant look unsightly. In the beginning, you can remove the leaves and burn them to help prevent the spread of the disease and then water your plants at the base to avoid getting water on the leaves. Water in the morning to give the leaves a chance to dry off before nightfall.

Is this powdery mildew?
powdery mildew Erysiphe necator Sign
Photo by Julie Beale

What is causing the cucumber leaves to be shriveled and deformed looking?

You may have aphids. Aphids can damage many garden plants from vegetables to flowers. They tend to congregate on the stems and under the leaves and suck the juices right out of the plant. Lady bugs are a natural predator and can be purchased online to be released into your yard where the aphids have been found. They will stay as long as there are aphids to eat.

What is damaging my cucumber plants?
Photo by John A. Weidhass

You can also use a sharp spray of water to remove the aphids. Spray under leaves and along the stems where aphids have been found.

What is causing leaves and cucumbers to have splotching coloring?

This sounds like the mosaic virus which is commonly spread by aphids. If you had a heavy aphid infestation, it makes it more likely that your plants can get the mosaic virus. Leaves will have varying shades of greens and yellows and the fruit can develop the same condition making the produce deformed, bitter and not of high quality.

Could mosaic virus be killing my cucumbers?
Cucumber Mosaic Virus Cucumovirus CMV Symptoms Photo by William M. Brown Jr.

Unfortunately there is no cure. Your best bet is to make sure you don't plant anything that looks like it might have the virus. This virus can spread to many of your garden plants so it's important to spot it early. If your plants develop symptoms, pull them immediately, burn them and avoid planting in that spot for the season. You can also grow varieties that are disease resistant.

Is this the result of cucumber mosaic virus?
Cucumber Mosaic Virus Cucumovirus CMV Symptoms
Photo by William M. Brown Jr.

A more extensive guide to cucumber problems can be found here:

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