Blossom Drop on Tomatoes

Due to the hot and humid weather, lately many gardeners are noticing “blossom drop” on their tomato plants. Blossoms are drying up and dropping off before the tomato fruit sets.

As explained by J.M. Kemble, Extension Vegetable Specialist and associate Professor, Alabama Cooperative Extension System:

“This condition is NOT related to any nutritional disorder, or any disease or insect damage. It is related to temperature. Despite the fact that tomatoes evolved in the tropics, flowering in tomato is sensitive to temperature. When day temperatures exceed 85°F and night temperatures exceed 72°F, tomato flowers will abort. An important factor involved with temperature is time of exposure. The longer the plants are exposed to these high temperatures, the longer the condition will last and the more serious the effect on flowering. Short exposures such as a week or less should not cause much of a problem. It is interesting to note that although the combination of high day and night temperature causes blossom drop, high night temperatures alone can be detrimental to flowering even if day temperatures are not over 85°F.

Older or heirloom, home garden varieties are more sensitive to high temperatures than many of the newer hybrids that are presently available. When fruit do not set and all other conditions are otherwise favorable (sufficient water and fertilizer, good pest control, appropriate pH) plants generally become vigorous and dark green. Even new hybrids, however, are susceptible to blossom drop.

Commercial growers in the southeastern US have suffered with this problem for many years until the recent advent of “heat set” tomato varieties. These varieties have been bred for tolerance to high day and night temperatures common in the summer and early fall. In fact, many of these varieties set fruit under poor growing conditions – extended cool, rainy periods as well as during extended periods of hot weather.

What to do: For this year or for an existing planting, keep the plants healthy. Keep plants well watered. Maintain fertility levels and control any pest problems as any additional stress will make the condition worse. The plants will produce flowers and set fruit when temperatures become more favorable.”

High levels of humidity can “gum” up the pollen in the flowers, preventing the pollen from moving from the anther to the stigma, which would normally result in pollination. Some gardeners have suggested shaking the plants to help the pollen move around.

Blossom drop is a frustrating, but (if the weather co-operates!) temporary problem.  You will likely still be enjoying a beautiful crop of tomatoes by the end of the summer!

This entry was posted in Beginner Gardeners' Guide, Commercial Growing, Growing Tips, Plant Diseases and tagged , . Bookmark the permalink.

7 Responses to Blossom Drop on Tomatoes

  1. Ingrid Hodnett says:

    Your article on blossom drop on tomatoes:
    I was telling my husband it must be with the excessive heat wave we have been having here in the north
    (Haviland Bay- near Sault Ste. Marie, Ontario -hub of the Great Lakes- in Canada)
    This was great to find out for sure the problem as it has happened to our tomatoe plants
    and yes my heirloom ones are affected.
    I have to say I surely enjoy you website, articles & your cataloque full of informative & interesting info for small scale home gardeners.
    I do have a question about celery if you can help me?
    I planted some Tango Hybrid Celery from seed beginning of April & I have lots of leaves approx one foot & 1/2 high with lots of small ribs only a few large & dark green (the ribs are only approx 10″ high
    Would you know when they should be ready? I have kept them very moist.
    Thank you so much-Keep up the great site….

  2. Crystal Rabe says:

    You say some new varieties of tomatoes will not have blossom drop in high day/nite heat,and also in extended cool or rainy periods. What are these varieties that are able to deal with the heat and also cool weather. I garden in a public garden in California. Last year most of us had few tomatoes because of an extended cool and foggy summer thru August… Many years there is east wind or long hot spells that interfere with tomato set. So I would be interested to know about these varieties of tomatoes. Could you send me a list of them and their traits with regard to heat/cool weater and blossom drop… Thanks , Crystal

  3. Vickie Julian says:

    Please, please tell us what the “heat set” tomato varieties are? I’m in North Carolina, and this heat wave is probably not a wave, but the new summer norm. I’d like to be better prepared for next year.

  4. Kate Webster says:

    I was set to ask the same question as the prior poster. I’m in VA and for the months of July & August the temperature ranges are routinely 10-15* above the optimal temperatures you list in this article. I wondered if you carried a variety of this “heat set” tomato as well. Thanks for your advice.

  5. Pingback: What’s Wrong with My Garden? Part 2: Demystifying Common Diseases | High Mowing Organic Seeds' Blog – The Seed Hopper

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