How to protect garden plants, fruit from sunburn
Q: I’m new to gardening in such a hot climate. During last month’s heat wave, some of my plants burned and are just starting to recover. With the hot weather predicted this week, how can I keep my tomatoes and peppers from getting sunburned again?
A: The summer heat in Redding can be brutal for both plants and people. With such intense sunlight during the summer it’s easy for plants and fruit to suffer from sunburn, especially if the plants become water stressed. Symptoms of sunburn start as yellow or tan discoloration on the sun side of the fruit or leaf. Tomatoes, peppers and eggplant commonly suffer sunburn, but other vegetable crops including melon, squash, cucumber, bean, pea and sweet corn can also suffer from sunburn damage.
There are several things that you can do to keep your plants or fruit from getting sunburned.
First you can shade plants by putting up a shade cloth or some other material that will provide shade to the garden area in the afternoon. Most vegetable plants need six hours of sunlight and during the intense light of summer, morning sunlight is best. Protecting plants from the hottest part of the day will not only keep plants and fruit from burning but also may keep plants healthier as they will be able to photosynthesize longer during the day. As temperatures rise the rate of photosynthesis decreases and photosynthesis will stop once temperatures in the leaf rise above 103 degrees. Shading the plant will help keep the plant canopy cooler.
Another way you can keep plants from getting sunburned is to water plants deeply in the morning to keep the plant from getting water stressed during the heat of the day. Plants may wilt in the afternoon, this is a natural response to the heat and low humidity, do not automatically assume that the plant is lacking water. It is best to check soil moisture before watering even if the plant is wilted, especially If you deeply watered the plant in the morning. Waterlogged soil can also cause plants to show signs of stress such as yellowing or drooping leaves.
In future years you can plan your garden to minimize sunburn on more susceptible plants by planting taller plants on the south or west side of the garden so that they shade plants that are more prone to sunburn. You can also use trellises for cucumbers or pole beans to shade plants that need some protection. Planting greens such as lettuce, chard, kale and spinach in the shade of other plants can also extend the season for these cooler season crops into late spring or early summer.
It’s also important to remember not to fertilize plants with a high nitrogen fertilizer during the hottest part of the summer as rapid growth can cause plants to become more water stressed and also new growth may be more susceptible to sunburn. Fertilizers can also increase water stress by adding additional salts to the soil, making it harder for the plant roots to uptake water.
The Shasta Master Gardeners Program can be reached by phone at 242-2219 or email email@example.com. The gardener office is staffed by volunteers trained by the University of California to answer gardeners' questions using information based on scientific research.