The Coastal Gardener: Use water wisely to cure heat stress

August 27, 2010|By Ron Vanderhoff
  • Sometimes leafy plants, like this squash, wilt because the air is just too hot and dry, not for lack of water in the soil.
Sometimes leafy plants, like this squash, wilt because… (Daily Pilot )

For better or worse, summer heat has finally descended upon our gardens.

Certainly, local gardeners will experience more periodic heat spells during the next two or three months, so how should a local gardener respond to these heat spells? With a cold glass of lemonade? Well yes, but what about our gardens?

Because a plant's reaction to heat is gradual, its impact is often misunderstood. In a futile attempt to mitigate heat stress, a gardener's usual response may only be to water more. But in many cases, more water won't make things better. In fact, it could only make things worse, promoting root diseases, which thrive in hot, moist, compacted summer soils.

Here are a few tips:

•Strong, well-rooted plants withstand heat better than weak plants or plants with small root systems.

•Check the soil. It may be dry on top, but moist a few inches below, where the roots are. Don't necessarily water because the soil surface looks dry.


•Make sure thirsty plants are well-watered before extreme temperatures hit. Usually that means watering in the morning or evening. Several plants will wilt during the hottest part of the day, no matter how wet the soil is. These plants are simply losing water through their leaves faster than their roots can replace it.

•A cool spritz of water on the leaves, not on the soil, will slow down a plant's water loss and perk the leaves back up, using surprisingly little water.

•If using a hose, be sure to let it run for a minute or two, until cool water comes out.

•Mulch, mulch, mulch. It keeps the soil from heating and drying out and conserves water.

•Many established California native plants can survive with little or no summer irrigation. They may enter a stage of "evergreen dormancy" while they hang on through the hot dry months. More water won't help and may actually harm them. Use restraint.

•Avoid pruning most plants during the summer. Removing too much leafy growth will expose the stems and branches to strong sunlight that can cause sun-scald.

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