What makes my cucumbers taste bitter? ASK THE HORT AGENT
Question What makes my cucumbers taste bitter?
Answer Cucumbers, as well as squash, cantaloupe, watermelon, pumpkin and zucchini, are in the Cucurbitaceae family. These plants have the ability to produce chemicals called cucurbitacins. Cucurbitacins are toxic at high levels, but they are so bitter that it is almost impossible for someone to consume enough of them to get sick. The most common side effect is an upset stomach. Plants grown in vegetable gardens have been selected for low levels of these bitter compounds (a notable exception is bitter melon used in Asian cuisine where the bitterness is a prized part of the flavor).
Bitter cucurbitacin is found mainly in the vegetative parts of the plant such as leaves, stems and roots. On occasion and to a lesser degree, it spreads to the fruiting structure. It doesn't accumulate evenly within each cucumber and can vary in concentration from one fruit to another on the same plant.
When preparing slicing cucumbers, keep in mind the bitter compound is likely to be more concentrated in the stem end than in the blossom end of the cucumber. It is also more prevalent in the peel and in the light green area just beneath the peel. It is less likely to be found in the deeper interior of the fruit.
Cucumbers growing under some type of stress, such as lack of water, extreme heat or cool periods, are often somewhat bitter. Misshapen fruits are more likely to be bitter than well-shaped fruits. Some scientists even think that varying levels of fertilizers, plant spacing and irrigation frequency may also affect cucurbitacin levels. Bitterness seems to vary with the type of cucumber grown. Expect some degree of bitterness from time to time in most any variety of cucumber.
Zucchini is the other vegetable that may be bitter. Unlike cucumbers, extreme bitterness in zucchini and summer squash is not influenced by the environment. Instead, zucchini bitterness is controlled genetically by one dominant gene. If a plant has the “bitter gene”, all zucchini produced by that plant will be bitter.
Not all news about cucurbitacin is bad news. Believe it or not, the corn rootworm (CRW) beetles actually like the taste of cucurbitacin. Pesticides have been developed that use this chemical like a bait. It is mixed with an insecticide. When the CRW senses the cucurbitacin, he immediately stops moving and starts eating the insecticide. The pesticide companies refer to it as “watermelon juice”. These pesticides have catchy names like Cide Trak, Invite and Slam.
Cucurbitacin is also used in traps to monitor CRW population densities. This helps the farmers or consultants decide when the numbers are high enough to warrant spraying. The bitter cucurbitacin doesn't appeal to other insects. Therefore, it doesn’t attract bees and beneficial insects.
If you want more info about cucumbers, then visit this website http://cuke.hort.ncsu.edu/cucurbit/cuke/cukehndbk/cukebitterness.html
If you do not have internet access, then call me at 910-893-7533, write me at PO Box 1089, Lillington, NC 27546 or email me at gary_pierce@ncsu.edu
Which lazy chef started the practice of leaving strips of peeling on the cucumbers? Peel your cucumbers, and drink “watermelon juice” made from the red part and not the green part.
Gary L. Pierce
Horticulture Extension Agent
Harnett County | 
