Regional Gardening Reports :: National Gardening Association

In the Garden:
Northern California Coastal & Inland Valleys
July, 2003
Regional Report

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This Redondo creeper (Lampranthus filicaulis) is for those who like it hot!

Beat the Heat

During the short, dark days of winter I dream of hot summer afternoons spent lounging in the shade. Now that those hot days have arrived, I complain that it's too darned hot. Although we don't get many days that extend into century territory on the thermometer, it only takes a few to get your attention. Thankfully, heat spells are usually short term here in Northern California.

Hot weather doesn't mean that you can sit back and put your feet up. No sir, on the contrary. You need to take precautions so that your garden survives the heat with as little damage as possible. Most important, of course, is watering. The time of day that you water is crucial. Watering should be done in the early morning hours while the temperature is on the rise. Watering midday in hot weather should be avoided except in emergency situations.

More Shade, Not More Water
Sometimes too much of a good thing is bad. On those really hot days, plants can't take up water fast enough to prevent wilting. The roots aren't able to keep up with the transpiration of moisture from the leaves, so wilting occurs. If the soil is already damp you may actually do damage to the root system if you water. It's best to shade the plant, if possible, to provide some relief from the sun so that the roots can keep up with demand.

This is especially true of new plantings. Baby plants haven't had a chance to develop mature root systems that will support them, and overwatering can be more of a problem than just letting them wilt. Tents made of newspaper or cheesecloth can be the saviors of a newly planted bed. It may not look nice, but it will save the plants. Just make sure there is adequate ventilation or you will cook them under the tents.

Showering Leaves Can Do More Harm Than Good
One hot summer day, when I was a neophyte gardener working for the City of Napa Parks Department, I felt sorry for some newly planted horse chestnut trees. I had been dragging hoses to water them weekly for their first summer until they became established and could survive on their own. Thinking I would cool them off, I splashed water all over their small canopies of tender leaves. The drops of water acted like magnifying glasses, and the whole row of trees burned to a crisp. Learn from my mistake: Don't get water on the foliage during really hot weather. This is true for ground covers (ivy especially) as well as trees.

Protective Sprays
Japanese maples and other plants with tender leaves can be protected from hot weather with a spray of Cloud Cover. This product is usually used during the winter months to protect plants from frost damage. It works as an anti-transpirant, sealing the pores on the leaves so that they don't loose moisture.

In general, plants with waxy or thick leaves survive hot weather better than those with delicate foliage. Waxy leaves don't lose water to transpiration, and thick leaves contain more moisture. However, any plant will suffer in the heat if it doesn't have adequate water prior to the hot weather. Listen to the weather reports and if you hear a heat spell is on the way, get out your garden hose!

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