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Squash blossoms dropping off #847745

Asked August 29, 2023, 10:21 AM EDT

Hi, I am growing some mostly healthy looking butternut squash plants, they have been flowering all summer but the blossoms curl up and then instead of fruiting they tend to fall right off. I've seen at least 25 or 30 blossoms between the 3 plants and only one seem to have turned to fruiting. They had some brief dry periods due to our dry weather but I tend to water them every day for the most part, had a bit of wilt a few times in the heat and some yellow near the stems. There has been a woodchuck roving about but the blossoms are still there, just fallen right off the stem. I touched one and it fell off, they're just barely attached. Is this a deficiency? The dirt is not the best. I planted them in small pots and transplanted them to my new garden plot I dug at my new house, but they were ready before I could introduce really good dirt. I also put wood chip mulch over the dirt to help retain water. Thanks!

Wabasha County Minnesota

Expert Response

Good afternoon Christina and thank you for reaching out to ask2.extension.  I found the following information on the U of M website.

Hot daytime, nighttime temperatures cause flowers to drop.  If you are still seeing flowers, but aren’t getting the tomatoes, peppers, beans or zucchini you are expecting, there can be a few heat-related factors in play.

The first is flower abortion: flowers form, but then die and fall off the plant before becoming fruit. Flower abortion can happen at temperatures ranging from 75° F to 95° F.

Dropped flowers have been noticeable in tomatoes this year. Tomatoes produce new flowers often, and the flowers have a 50-hour-long window in which to be pollinated. When tomatoes are exposed to sustained hot temperatures (more than 85° F in the day and 70° F at night), the tomato plant becomes stressed and burns through its energy stores. This changes the flowers, making it harder for them to be pollinated, and the blossom often drops out without pollination occurring. So during 50-hour periods that have hot days and especially hot nights, a round of tomato flowers are likely to drop off without pollinating.

Vining vegetables in the cucurbit family (pumpkins, squash, melons, cucumbers, and the like) produce male and female flowers. Look at the base of the flower to tell the sex.

Female cucurbit flowers will be swollen underneath in the area that will eventually become the pumpkin, zucchini, etc.

Male flowers will have just a straight stem.

Depending on the variety of the vine crops, hot temperatures can change how many male and female flowers are present. Typically, high temperatures (over 90° F during the day and 70° F at night) develop more male flowers than female flowers. This means that we may be seeing zucchini plants with prolific flowers and few fruit, because the flowers we are seeing are all male, thus do not produce the part of zucchini we like to eat.

This isn’t going to make you feel better.  Maybe if you can keep your plants alive until it cools off, you may get some yet.  This has been a tough summer.


Deb Kroon Replied August 29, 2023, 6:39 PM EDT

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