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Consumer Horticulture

Department of Horticulture and Landscape Architecture

Yard and Garden News


Hot Weather Is Tough on Plants Too!

(Released: 20 July 1995)

By B. Rosie Lerner
Extension Consumer Horticulture Specialist

As if gardening chores aren't strenuous enough by this time of year, Mother Nature's heat wave is making life even more difficult.

Tomatoes, peppers, melons, squash, pumpkins, cucumbers and beans often drop their blossoms without setting fruit when day temperatures are above 90 degrees Fahrenheit. There's not much you can do but wait for cooler temperatures to prevail. As more favorable conditions return, the plants will resume normal fruit set.

Sweet corn also is likely to have trouble setting fruit in such hot weather. Unfortunately, you only get one flush of flowering with corn, so if your plants happen to be shedding pollen now, you can expect poor "ear fill" later.

Cool season crops, such as lettuce and spinach, will bolt, or produce seed stalks, causing the flavor of the leaves to become bitter. It's best to remove these crops and replant with heat-tolerant vegetables such as beans, carrots or chard.

Newly set transplants will require more frequent watering and will benefit by shading from midday sun to avoid wilting. In some cases, plants will wilt during midday despite all your efforts simply because the leaves are losing moisture faster than the root system can take up water. In this case, the plants should recover in the evening and morning hours when temperatures are cooler.

Extremes in temperature and soil moisture often bring on blossom-end rot, a dry, leathery scarring of the blossom end of the fruit on crops such as tomatoes, peppers and squash. Irrigating during dry periods and mulching to conserve soil moisture will help minimize this problem.

Container plants on the patio really will be stressed by the heat wave since they have much less buffering of temperature extremes on the root system. In addition to watering more frequently in hot weather, provide afternoon shade if possible to help keep them a bit cooler.

The good news is that a return to normal summer heat will feel pretty good after this wave is over! In the meantime, try not to overdo the garden work; over-exerting yourself in extreme hot weather can be very dangerous to your health. Aim to complete your chores very early in the morning; take frequent breaks; and drink plenty of water to keep yourself from wilting.


Last updated: 10 April 2006
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