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Summer is in full swing and so is harvest in the vegetable garden, with the first summer squash, zucchini and cucumbers. In many small towns, soon you won’t be able to leave your car parked with the windows rolled down or you might come back to find the front seat full of zucchini or cucumbers!
Both cucumbers and zucchini are members of the Cucurbit family, which also includes pumpkins, melons, squash and gourds. Bitterness is a common problem of zucchini and cucumber and very frustrating to gardeners who have carefully tended the plants for several weeks, only to find the vegetables too bitter to eat. What causes this bitterness?
All cucurbits produce chemicals called cucurbitacins, which cause the vegetables to taste bitter and served as a defense against plant-eating wildlife. Cucurbitacin also contributes to the musky scent of cantaloupe. Naturally, higher cucurbitacin concentrations cause vegetables to be more bitter. Wild cucurbits, including wild cucumber and buffalo gourd, contain such higher levels they are inedible.
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In commercially cultivated cucumbers and zucchini, plants have been bred with low cucurbitacin concentrations making the vegetables more tasty for us.
Environmental stress — high temperatures, wide temperature swings or too little water — can cause mild bitterness. This is a common occurrence, especially in later summer, and is caused by higher cucurbitacin levels triggered by environmental stress. Uneven watering practices (too wet followed by too dry), low soil fertility and low soil pH are also possible stress factors.