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Once slicing and salad cucumbers like this Asian variety reach an ideal length, they should be harvested while they are still slender.

Courtesy Meredith Seaver, USU Extension

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This overgrown cucumber has a much higher chance of being bitter than if it had been harvested a few days earlier.

Courtesy Meredith Seaver, USU Extension

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A deep soak once or twice a week and mulch over the soil can reduce plant stress and the chances of bitter cucumbers.

Courtesy Meredith Seaver, USU Extension

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Pickling cucumbers are more likely to develop bitter flavors than slicing cucumbers. They benefit from being harvested when smaller than this cucumber.

Courtesy Meredith Seaver, USU Extension

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Some of our cucumbers are bitter. I’ve heard that once a plant produces bitter cucumbers it will always produce bitter cucumbers. Is it really a lost cause? Should I pull out the plant?

That bitter flavor that you tasted in your cucumber is cucurbitacin, a natural defense compound in cucumbers and other members of the Cucurbitaceae family (cucumbers, squash, melons, gourds, watermelons). Cucurbitacin is found in the roots, stems and leaves of cucumbers and sometimes in the fruits. It’s the cause of the digestive discomfort some people experience after eating cucumbers.

While there isn’t one specific cause of bitter cucumbers, here are three things most vegetable specialists agree you should keep in mind:

Bitterness in cucumbers is related to a combination of variety and environmental stressors. Some varieties, especially some of the older varieties, are prone to bitterness. Pickling cucumber varieties also tend to have more problems with bitterness than slicing or salad varieties.

Plant breeders have been bringing new less-bitter varieties to the vegetable growers market over the last few decades and continue to release new bitter-free varieties today. Check catalog descriptions if you want to replace an older variety that you’ve been growing. Look for varieties described as burpless, sweet or tasty in the name. Most of the newer hybrids with the slender, longer fruits that are popular with home gardeners lately have a sweeter quality.

When it comes to environmental stresses and growing conditions, cucumbers may be the Goldilocks of the vegetable garden. Both high temperatures and overly cool growing conditions are suspected stressors that can contribute to bitterness. Cucumber plants need warm, sunny locations. If conditions are cool or shady, they are more prone to bitterness. Planting and growing cucumbers when overnight lows drop below 55 degrees can cause chilling injury and increase the chances of bitter cucumber fruits. However, when temperatures are too hot, they are also more likely to develop bitter flavors. To be fair to the cucumbers, there are very few vegetables that do well with temperatures above about 90 degrees.

Cucumbers are also more prone to bitterness when they are watered too much or too little. Consistent watering – a deep soak once or twice a week – is just right for them. Adding a layer of mulch over their root zones will reduce large swings between wet and dry conditions.

Poor soil conditions and poor plant nutrition can also contribute to bitterness. Pay attention to your soil preparation before planting. Have your soil tested and use the test results as your guide for managing the fertility in your garden soil. Whatever source you choose for adding nitrogen to your garden, keep the amount in the Goldilocks range – enough is just right, but adding extra is too much.

Cucumbers that are left on the vine for too long after they reach their ideal size are more likely to be bitter. For cucumbers that are more prone to bitterness, extra time on the vine allows more cucurbitacin to accumulate in the fruits. Pick your cucumbers often to avoid overgrown cucumber fruits. The catalog or packet description for the variety you chose will help you decide what size is just right.

Bitterness in cucumbers is usually concentrated at the stem end and under the skin. You may be able to rescue a bitter cucumber by cutting off an inch or two of the stem end, peeling the cucumber and rinsing it off to remove the bitterness. Sometimes you need to peel deeply.

So, should you pull out your cucumber plants? Before doing that, try changing the way you take care of your plants as that can sometimes reduce the problem. You can’t do anything about the hot weather, but you can make sure the plants are watered deeply and consistently. Don’t wait until your cucumbers are wilting to water them. Keep a layer of compost or grass clippings over the soil to keep the soil cooler and more evenly moist. Then give the plants some time to produce new cucumbers.