The extent of bitter compounds will vary from fruit to fruit as well as within individual fruits. The compounds are likely to be more concentrated at the stem end than at the blossom end of the fruit. Bitterness, if present, is always found in and just under the skin of the cucumber and not deep in the fleshy portion or in the seed locules. The amount of bitterness cucumbers contain varies from year to year. There are many theories about bitterness but it has been difficult to obtain consistent information as to its cause.
Temperature appears to be one cause of bitterness.
More complaints of bitter cucumbers will generally occur during a cool growing season than during a warm one. Research has shown that fertilization practices, plant spacing, and frequency of irrigation have little consistent effect on the number of bitter cucumbers produced. Yield and quality of cucumbers will, of course, be increased with optimum irrigation and fertilization through the picking season. Contrary to the belief of some people, the direction of peeling does not have an effect on the spread of bitterness in a cucumber fruit. Different varieties of cucumbers vary widely in their tendency to be bitter.