Make sure your garden can handle triple-digit heat

Can your summer garden take the heat? This week, you’ll likely find out.

With countless young tomato plants now in the ground, Sacramento-area vegetable gardens are now experiencing their first real temperature test as afternoon highs flirt with triple digits.

Tomatoes love warmth, but 100-degree days can hamper growth and pollination. Maintaining consistent soil moisture (not too much or too little) is key to their comfort. (That’s where mulch is vital.) Encourage their roots to grow down with infrequent, deep watering -- the deeper their roots, the better they cope with summer stress.

How much water? It depends on the size of the tomato plant. An average size plant (growing to the top of its tomato cage) needs 5 gallons a week, split into two applications. During hot weather, double that.

Seedlings and new transplants are most at risk during hot weather. They don’t have the root system or support to withstand adverse conditions. The low humidity that accompanies this current heat wave sucks the moisture out of leaves. Squash and other big-leaf veggies can be quick to wilt.

This first real heat of (almost) summer could take a toll on your garden. Your new transplants aren’t used to these extremes.

Take some time now to help your whole garden cope with heat. Not only will your plants stay better hydrated, they’ll suffer less disease, too.

Here’s heat-related advice from UC master gardeners and our own experience:

* Stay hydrated! That applies to both you and your garden. Water early in the day – before 8 a.m. if possible – to cut down on evaporation.

* Switch to drip irrigation if possible. Drip irrigation puts water where plants need it – at the roots.

* Check the soil before you water. It may look dry on top, but still have enough moisture in the root zone 6 inches below the surface. Plants can suffer from too much water (especially in containers) as well as not enough.

* Examine your sprinklers and irrigation system for leaks and clogs, even if you did so at the beginning of spring. Things happen. Now is the time to make adjustments and repairs before plants suffer.

* Prioritize your watering. Deep-water trees and shrubs, your landscape’s most valuable and slowest-growing plants.

* Create water basins around trees, shrubs and many summer vegetables such as tomatoes, peppers and eggplant. A basin holds in extra water just a little longer so it slowly seeps into soil. It’s easy to make a basin: Around the plant, build a soil berm about 3 inches high and at least 1 foot from the main stem (for tomatoes) to 6 feet (for trees). But don’t let water stand against trunks or main stems; that can cause crown rot.

* Cycle and soak. Water needs a chance to soak in, especially if you have clay soil. Otherwise, it will run off (and down the drain) instead of reaching roots. Run your irrigation for a short period. Wait an hour or two. Then, run your system again. The water from the second cycle will reach deeper than the first.

* Mulch, mulch, mulch! A layer of 3 inches of straw, wood chips, dried leaves or other organic material will keep soil and roots cooler while conserving moisture. Leave a circle open around the trunks or main stems of plants (this is to avoid crown rot and other issues). Mulch conserves moisture and keeps plant roots comfortable. It also adds nutrients to the soil, protects soil microbes and controls weeds. Don’t mulch with rocks or gravel; those materials absorb heat and actually make the soil – and roots – hotter.

* Don’t fertilize when it's over 95 degrees. Plants are trying to keep the leaves and flowers they have already; they don’t need to add more. Wait until the weather cools down to normal (in the 80s). And always water BEFORE fertilizing.

* Shade any sensitive plants and developing fruit on tomatoes, peppers, eggplant and squash. Your harvest can get sunburned. Protect from intense afternoon rays with temporary shade such as shade cloth, burlap draped over trellises or even a propped-up umbrella.

* Wilting can be normal. Some big-leaf plants such as squash may seem to wilt every hot afternoon; that’s OK. They recover overnight. It’s when they’re still wilted in the morning that it’s a problem.

* One good thing about high heat: It wipes out many fungal disease problems. Powdery mildew disappears as the temperature rises.

* A stressed plant draws pests. Keep an eye out for invasions by aphids, thrips, spider mites and tomato hornworms so they don't become established on your plants.