Ask Mr. Smarty Plants

There is agreement on what compounds cause the bitterness in cucumbers. They are cucurbitacin B and cucurbitacin C and these occur in all parts of the plant—leaves, stem, roots—but rarely in the fruit. Another compound produced by the cucumber, an enzyme called elaterase, modifies the cucurbitacins to reduce their bitter flavor. The variable amount of bitterness found from year to year or from plant to plant or even from fruit to fruit on the same plant is thought to depend on the activity of the elaterase. Environmental conditions—temperature or moisture, for instance—may affect the amount of elaterase produced. However, there is no clear agreement on exactly what those environmental factors are. Sources in the northwest and in California cite cool temperatures as being a major cause for the bitterness; whereas, Texas A&M PlantAnswers implicates hot temperatures. Temperature stress might be a better description of the cause of bitterness. There is some evidence that water stress could also be responsible. One thing that you might try is being sure that your plants are well watered. This could result in the fruits that are developing now being less bitter.

One solution you may have is to peel and trim your cucumbers extensively before you eat them. The stem end typically is bitterer than the flower end of the fruit. Also, right under the skin is usually bitterer. By careful peeling away of the skin and some of the outer flesh and removing more of the stem end of the fruit you may be able to enjoy the ones you have.