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How to Prevent Heat Stress in Your Garden Plants

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Heat stress in garden plants is a real problem during July and August in much of the country. Extended periods of high heat (particularly when the heat index roars over the 100 degree mark) can take a real toll on your garden.

Here are a few tips for helping different plants in your garden through a hot, dry spell and keep them healthy and productive.

Vegetable Gardens

Vegetables need a reliable, steady water supply to stay productive. However, even with careful watering, your veggies may suffer from heat stress. The most common signs of heat stress in vegetables are sunburned foliage and fruits (usually yellow and crisp to the touch), blossom and fruit drop, and wilting. There are a few things you can do to help your vegetable garden through a prolonged hot spell:

  • Water regularly and deeply.
  • Mulch the soil with at least three inches of organic mulch to reduce moisture loss and help regulate soil temperature.
  • Shade certain crops, such as leafy greens and lettuces, to slow bolting. They will bolt, no matter what, during periods of intense heat. However, giving them some shade may buy you a couple of days before plant quality is diminished.

Lawns

Many lawns, including bluegrass, fescues, and ryegrass, naturally go dormant (turn brown and stop growing) during periods of high heat and drought. The easiest thing to do is just let nature take its course. Once temperatures return to normal, and the lawn starts getting adequate moisture, it will green up again.

However, if this is not an option (due to homeowner association bylaws or other issues) you can keep your lawn green by providing at least an inch (up to two inches during high heat) of water, delivered slowly and steadily, per week. Don't just throw the sprinkler out there for an hour -- if the soil is very dry, chances are likely that most of the water you apply will simply run off. Give the lawn a slow, short watering first to let the moisture soak into the soil. Then, later on or the next day, give it a long, deep watering. If you start seeing water running off onto your sidewalks, STOP -- you're just wasting water at that point.

It would also help to avoid cutting the lawn (it's not growing much in the heat anyway) so that you don't stress it further.

Trees and Shrubs

Newly-planted trees and shrubs (less than two years since planting) can be hit particularly hard by heat and drought. To keep them alive and healthy:

  • Give them between two and four inches of water per week during very high temperatures (heat index above 100 degrees) and drought.
  • To water, a long, slow trickle is best. This will allow the water to soak deep into the soil without running off, ensuring that the water is going to the root zone where it is needed.
  • Shrubs can be misted several times per day to increase the ambient moisture -- this will prevent the foliage from drying out too much.
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