Do your plants suffer from summer sunburn?

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Last Updated: 
November 20, 2003

SALEM – Are some of your plants suffering from sunburn? The long sunny days and hot temperatures of summer can lead to sunburn on some plants.

Yellowing on leaf tissue - particularly on the south side of the plant - is a common symptom of sunburn in plants, explained Neil Bell, home horticulturist for Polk and Marion County offices of the Oregon State University Extension Service. Small sunburned plants may be yellow all over. The yellowing may have some brown patches, especially if the plant is planted in the wrong place.

Rhododendrons and hostas are commonly chronically sunburned when they are mistakenly planted in full sun. Some varieties are better adapted to sun than others. Check at the time of purchase for sun tolerance. Others prefer a partially shaded site.

Newly planted plants or young plants with underdeveloped root systems are particularly susceptible to sunburn.

"Young plants are pushing extension growth," said Bell. "Their water requirements are at a maximum. Also root systems are still developing. If this weren't enough, the days are still long, so plants might have to put up with sunlight for 12 to 14 hours."

Berries can also show signs of sunburn, especially the red raspberry and blackberry.

Sunburned raspberries have white "drupelets," on the sun-exposed side of the berry. Drupelets are those tiny round sections that make up a raspberry. These colorless drupelets do not otherwise affect the quality of the fruit, said Bell. You can still eat them.

In blackberries, the dark colored fruits absorb heat, especially on the sun-exposed side. When sunburned, droplets of trailing varieties can become red and soft and taste overripe. But they still are edible.

In erect varieties of blackberries, the fruits may become hard and dried, rendering them inedible, said Bell.

Gooseberries can exhibit browning if sunburned. Grapes rarely get sunburned except if leaves are removed late in the season, exposing previously shaded grapes to full sun.

The best way to prevent sunburn is to know your plants' requirements for sun or shade before you plant them, then plant them in the right place, said Bell. But, if they are already in the ground and are getting sunburned, either transplant them to a better site or amend heavy soils with compost so the plant can develop better roots. Make sure your plants are getting enough water and fertilizer for optimal health and minimal stress. A short-term solution for sunburn might be to protect them with shade cloth.

Author: Carol Savonen
Source: Neil Bell