Weather Garden Woes
By Melinda Myers
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[August 11, 2022]
Poor flowering and misshapen or a lack of fruit
on tomatoes, peppers and squash may be due to the weather, not your
gardening skills. Temperature extremes can interfere with flowering
and fruit set on these and other vegetables in your garden.
We watch for and can’t wait to taste that first
red ripe tomato. It is certainly frustrating when we see flowers
drop or the plant fails to form fruit. Tomatoes thrive in warm sunny
conditions; but temperature extremes can prevent fruiting, cause
misshapen fruit, or reduce the size of the harvest.
When daytime temperatures rise above 90°F and night temperatures
remain above 70° F blossom drop and poor fruit development may
occur. Combine this with low humidity and the pollen is not viable.
In hot and humid conditions, the pollen is too sticky and doesn’t
move from the male to the female part of the flower. Without
pollination the flowers won’t be fertilized, and fruit will not
Cool weather can result in poor fruiting. Night temperatures below
the optimum of 59° to 68°F will reduce the amount and viability of
pollen that the plant produces. Less viable pollen means fewer fruit
will form. Cooler temperatures below 55°F can result in misshapen
fruit and catfacing. Fortunately, the malformed fruit is still tasty
and safe to eat.
Temperature extremes also impact pepper productivity. When
temperatures climb to 95°F or higher the pollen is sterile and
flowers may drop. Small fruit may also fall from the plant during
such hot spells. Pepper plants also experience poor fruit set when
night temperatures drop below 60°F or rise above 75° F.
Tomatoes and peppers aren’t the only vegetables impacted by
temperature extremes. Eggplants, a close relative to tomatoes and
peppers, do not set fruit until night temperatures are above 55°F.
Beans stop flowering or the flowers die when temperatures rise above
Flowering in squash and cucumber plants is also influenced by
temperature and other environmental factors. These plants produce
separate male and female flowers. The male flowers usually appear
first and it is not until both the male and female flowers are
present that pollination, fertilization and fruit production can
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Research found cool temperatures, bright sunlight,
and shorter days encourage female flower production while male
flowers are more prolific during warmer temperatures, less sunlight
and close spacing. Flowering on squash and cucumbers is also
impacted by nitrogen fertilization. Too much can prevent female
flower formation while insufficient amounts can reduce the number of
The simplest solution is to wait for optimum temperatures and the
proper humidity levels to return. Once this happens, the plants will
begin producing fruit.
If poor productivity related to the weather is a yearly problem,
consider planting more heat tolerant varieties, adjust planting
times and look for more suitable growing locations.
When the harvest is delayed, extend the season with the help of row
covers. These fabrics allow sunlight, air, and water through while
trapping heat around the plants. Just loosely cover plants and
anchor the edges with stones, boards, or landscape stapes when frost
is in the forecast. You can leave the fabric in place for the
remainder of the year. Just lift it to harvest and secure the fabric
If this summer’s weather leaves you disappointed with the harvest,
remember there is always next year.
Melinda Myers has written more than 20 gardening books, including
the recently released Midwest Gardener’s Handbook, 2nd Edition and
Small Space Gardening. She hosts The Great Courses “How to Grow
Anything” DVD instant video series and the nationally syndicated
Melinda’s Garden Moment TV & radio program. Myers is a columnist and
contributing editor for Birds & Blooms magazine and her website is
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