| B. Rosie Lerner
Hot Weather Tough on Plants and
Sultry summer weather is not only tough on gardeners but on our plants
as well. In addition to garden and landscape plants gasping for water,
some vegetable crops have trouble producing when under stress.
Tomatoes, peppers, melons, squash, pumpkins, cucumbers and beans often
drop their blossoms without setting fruit when day temperatures are above
90° F. There's not much you can do but wait for cooler temperatures to
prevail. As more favorable conditions return, the plants will resume normal
Sweet corn is also likely to have trouble setting fruit in such hot weather.
Unfortunately, you only get one flush of flowering with corn; so, if your
plants just happen to be shedding pollen when the weather is stressful,
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 out on the patio will really 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 weather is always changing. The extreme heat won't
last forever--it will just seem like it! In the meantime, try not to overdo
the garden work. Aim to complete your chores very early in the morning
or in the evening when the sun is less intense, take frequent breaks and
drink plenty of water to keep yourself from wilting.