Bitterness in Zucchini Squash and Cucumber

• Adapted from an article by Sarah Browning and Dr. Laurie Hodges
• Department of Horticulture, University of Nebraska, Lincoln, NE 68583

A common problem found in zucchini squash (Cucurbita pepo) and cucumber (Cucumis sativus) is bitterness, and it can be very frustrating to gardeners who find the vegetables too bitter to eat. Cucurbits produce a group of chemicals called cucurbitacins.

Mild bitterness is common in cucumbers, and is caused by environmental stress, including high temperatures, wide temperature swings or too little water.

Occasionally, zucchini can be bitter. Extreme bitterness has also been observed in summer squash (Cucurbita pepo).

Extreme bitterness in zucchini and summer squash is not influenced by environment, but is genetically controlled by a single dominant gene.