Hot tomato! What's wrong with those vines?

According to the National Weather Service, Sacramento is in for another stretch of triple-digit heat. Six of the next seven days are expected to top 100. (Sunday, July 21, is the exception with a forecast high of 95.)

We have a reputation for summer heat, but this is ridiculous. In the first 18 days of July, Sacramento hit 100 or more 11 times. (Make that 12 out of 19, with Friday’s expected high of 105.) Twice, we reached 110 degrees. Normal for July in Sacramento: 92 degrees.

This extended heat wave has had a major impact on our summer gardens. Most noticeably, few if any tomatoes are setting. The ones that do form seem to have bleached patches on their skin – a sign of sunscald.

Prolonged triple-digit heat waves can toast tomatoes and other sun-loving crops such as peppers and eggplant. Tomatoes in particular tend to be temperature sensitive. Peppers, with thin skins, also can develop sunscald.

When temperatures stay above 95 degrees, tomato flowers may drop off or refuse to set fruit. Leaves can fry and turn crispy. Ripening tomatoes may split or develop calluses.

By now, you should know the drill: Water, water, water. But how much? And when? This advice comes from UC Cooperative Extension master gardeners as well as longtime local tomato growers.

* Water early and deeply. Irrigate your tomatoes in the morning, making sure water reaches down at least 6 inches into the soil. How do you know? Test the soil with a probe or long screwdriver; it should easily plunge into the soil. Or use a trowel, dig down and look. (Or invest in a soil moisture meter, an invaluable tool.)

* During hot weather, water tomatoes two to three times a week. Tomatoes normally wilt during a hot afternoon; that’s OK. But if they’re wilted in the morning, water immediately. (Note: A few heirloom varieties, particularly of Russian origin, have a natural tendency to wilt all the time. But if you are growing one of these, you've probably noticed this already.)

* Tomatoes planted in containers may need extra water every day during hot weather. Their potting soil tends to dry out faster.

* Keep watering consistent and don’t let soil dry out completely. That can lead to blossom end rot, the hard brown callus on the flower end of a tomato.

* Mulch is your friend. Make sure your vines have at least 2 to 4 inches around them to help keep roots cool and soil evenly moist. Straw, leaves or shredded bark make the best tomato mulch. Many gardeners prefer straw (not hay) because its light color reflects intense sun rays instead of absorbing that added heat. (Also, hay contains seeds that can sprout and suck nutrients out of soil.)

* Don’t fertilize during a hot spell. Feeding now just puts more stress on the plant.

* Tomatoes need “full sun,” but they can get sunburned. If leaves or developing fruit look bleached out or burned, give your vine some afternoon shade. Erect a temporary shade structure by draping burlap or shade cloth over the tomato cage or trellis. This also helps prevent fruit from cracking. Note: Sunburned or cracked tomatoes are edible -- just cut around the damaged parts, but do it quickly, before bacteria or mold sets in. The good bits can be roasted or frozen for later use.

* If foliage turns brown, leave the dead leaves in place for now. They help protect the fruit from sunburn. After the heat has subsided, prune off the completely dead leaves so new foliage can grow.