Malformed zucchini

Asked July 2, 2018, 8:32 AM EDT

I'm growing several zucchini plants from seed. They formed and flowered very well -- producing male and female flowers. The first few fruits were normal -- dark green, fully sized. However, the subsequent fruit formation has been way off. They are turning yellow very quickly and now shriveling up when still small. Any idea what may be causing this? I'm including photos of the malformed fruits and one showing the first few regular ones. Thanks.

Montgomery County Maryland vegetables abiotic issues poor pollination

4 Responses

When the female flowers opened there was insufficient pollen (no male flowers) or insufficient pollinator activity. This caused the developing fruits to shrivel. It's a temporary problem.

there Pollinator insects move pollen from the male flowers to the female flowers where the pollen can fertilize the ovules (tiny seeds) inside the ovary (the very small fruits that appear below the female flowers). When the seeds are fertilized the fruit enlarges. Twisted or deformed squash are the result of insufficient pollination.

Blooms on plants in this family typically are only open for one day. Blooms will simply drop off the plant if they are not pollinated. This can be caused by low bee activity due to cool, wet temperatures or from pesticide sprays. Undeveloped fruits will drop off with blooms or may drop several days afterward due to the same lack of pollination and fertilization. Do not apply insecticides (other than insecticidal soap or horticultural oil) in the vegetable garden during the bloom period.jt

Are you growing in a fabric "grow bag?" Can you send me a photo of the bag and plant and information on the size of the bag. We can use that information to expand our container gardening content. You can send photos and info to:
Jon Traunfeld- jont@umd.edu
Thanks!

Thanks for your reply. I do know about pollination. Actually there are many more male flowers than female flowers. I have twice tried to hand pollinate them when both a male and female flower were open at the same time. I saw a bee in a male flower today, but there was no female flower open. There are plenty of fruits forming, but they are becoming deformed later. I'm not using any pesticides. Are there any other steps to encourage more flowers? I have loads of flowers nearby to attract pollinators.

All you can do is brush pollen from the male flowers on the female flowers and do this in the morning. You will have to be patient. Here is our profile on squash http://extension.umd.edu/hgic/plants/summer-squash

mh