Why Are My Cucumbers Bitter?

“I am growing the same cucumbers this year as last year.  Every cucumber this year looks beautiful but tastes very bitter and is inedible.  I believe I am providing adequate water, though due to the heat the plants still wilt during the day. What can I do to improve the flavor? ” Lisa of Marietta, Pennsylvania

Answer: There are two things that can cause cucumbers to become bitter – the cultivated variety and environmental stress (heat stress, water stress, or disease). A great Oregon State University (OSU) article on the subject quotes the vegetable breeder, Jim Myers of OSU. He explains that the source of cucumber bitterness is caused by the natural plant chemical, cucurbitacin. It exists in high quantities in the leaves and stems of cultivated cucumbers. During stressful summers, concentrations can build up at different levels in the cucumber fruits as well; often at the blossom end. What’s odd is that sometimes a single plant may have some bitter fruits and some nice-tasting cucumbers, so taste each one to double-check before composting. The same plant may also produce sweeter fruits as growing conditions become better.

Non-Bitter Cucumber Varieties

Some varieties tend to reliably produce sweet cucumbers, even under stress. Here are five excellent cucumbers that resist bitterness.

  1. Katrina‘- The crisp, seedless, Beit-Alpha-type cucumber is also very disease-resistant and stays sweet.
  2. ‘Jibai Shimoshirazu’ – This heat-tolerant, Japanese snacking cucumber never gets bitter!
  3. ‘Green Light‘ – There is a reason that this cucumber was a 2020 All-America Selections winner. Its fruits are crisp, sweet, prolific, and resist bitterness.
  4. Marketmore 97– This classic, disease-resistant cucumber is known for its ability to stay sweet, even when stressed.
  5. ‘Unagi’ – After reading about this one, I plan to grow it next year. Its hybrid cucumbers are crisp, sweet, and very prolific.

I also recommend that you watch the video below to learn how to grow cucumbers to perfection. I know that it can be difficult in years where high heat, drought, and even excess rain are problems, but the video contains some good growing tips.

Happy gardening,

Jessie Keith

Black Gold Horticulturist

Why Aren’t My Cucumbers Fruiting?

Female cucumber flowers have underdeveloped baby cukes at the base while male flowers do not.

“Why are my cucumber plants not setting many cukes?  The blossoms fall off before setting.” Question from Ron of Cashmere, Washington

Answer: There are several possible reasons that your cucumbers are suffering from blossom drop before fruit set. These include pollination issues, environmental stresses, and soil nutrient problems. Let’s take a closer look at these possibilities.

Cucumber Pollination

Cucumbers are dioecious. This means that they have separate male and female flowers on the same vine. Male blooms appear first on the vines and will open and drop. A week or two after the male flowers appear, you should start to see female blossoms on the vines. These are easy to spot because they have undeveloped baby cucumbers at the base of the flowers. It could be that not many of your female flowers have appeared yet. Check to see if the flowers that have dropped have little underdeveloped fruits at the base. If not, they are male flowers and your fruiting females may just be getting started.

Once you have both male and female flowers on your vines, bees pollinate the females. If your yard has few bees, fruit set can be a problem. Look for bees, and if you don’t see any, you may have to try moving pollen from the stamens of the male flowers to the central pistil of the female flowers. This is easily done with a small brush or Q-tip. Another option is to choose a self-fertile cucumber variety, like the award-winning ‘Diva’, which does not need pollinators for fruit set.

Cucumber Plant Stresses

Healthy vines will lack spots or wilting leaves.

Seasonal temperature extremes–above 90 degrees Fahrenheit and below 60 degrees Fahrenheit–can induce flower drop and inhibit fruit set. Too little or too much water can too, though in both instances you will see overall vine decline. There are also many cucumber diseases that can inhibit plant vigor and fruit set (click here for an expansive cucumber disease list), but once again, you will see signs of poor plant health.

Cucumber Nutrient Needs

Choose a vegetable fertilizer formulated for fruiting crops for vigorous fruiting. Soil that is too high in nitrogen can inhibit flower and fruit set. Cukes also need organic-rich soil with a near-neutral pH (6 to 7) grow to their fullest (Black Gold Garden Soil is a great soil amendment).

I hope that this info will help you determine the root cause of your cucumber problems. To learn more about cucumber growing success, watch the video below.

Happy Gardening,

Jessie Keith

Black Gold Horticulturist