New zucchini not growing to full term

Asked July 2, 2013, 1:08 PM EDT

Most of my young zucchini seem to grow to a small size, then turn yellow on the end and eventually die. Do I need to feed them more, water them more, or water them less. I am growing them in a raised bed in full sun and watering them during this heat once a day with a 1/4" drip line system.

Jackson County Oregon

1 Response

The likely reason for summer squash fruit not developing to maturity (falling off the stem, shriveling at the end of the fruit, remaining very thin and small) is lack of pollination. Your problem may be related to a lack of pollen at the time the female blossom was open; a lack of bees or other insect pollinators to transfer the pollen, or rain at the time pollination should have occurred (blossoms have a short open period, then close).

Both male and female flowers develop on the same plant. During the main growing season the ratio of male female flowers is usually 3:1. The female flower has a miniature fruit at the base and is on a short stem whereas the male is on a longer stem. Pollen must be transferred to the female flowers from the male flowers for fruit to develop, and this is mostly done by honeybees. If you need to use insecticides, use them late in the evening to reduce the risk of killing the honeybees.

While easy to grow, zucchini, like all squash, requires plentiful bees for pollination. Where bee populations are in decline or there is high pesticide use, such as mosquito spray districts, gardeners often experience fruit abortion, where the fruit begins to grow, then dries or rots. This is due to not enough pollen grains delivered to the female flower. When no bees are present in the garden, you can pollinate by hand. It can be tedious but is the only way to achieve fruits in the absence of bees. Pollen is yellow and is produced on the structure in the center of the male flower. Use an artist small brush to transfer the pollen or you can break off a male flower, remove the petals to expose the pollen-bearing structure and roll the pollen onto the stigma in the center of the female flower. It is important to use only freshly opened flowers; they open early in the morning and are receptive for only 1 day.

Gardeners often become concerned when there are early flowers that don't make fruits. All of the earliest flowers are males (except in hybrid varieties) and female flowers follow shortly.