A sunburned schefflera struggles in the wake of a scorching four-day heat wave.
A record-breaking heat wave left plants, shrubs and trees throughout the Pacific Northwest burned out and devastated.
There’s no denying the damage is severe, said Heather Stoven, OSU Extension horticulturist. Some plants died and others were fried by the record-breaking temperatures. However, even some that look extremely bad, like rhododendrons and hydrangeas, can bounce back. Burned leaves don’t necessarily equal a dead plant, so patience and observation is needed.
Here are some recommendations from Stoven and other experts:
• Go ahead and cut off dead flowers, but try to resist the urge to remove partially dead leaves, and especially don’t do any hard pruning. Leaves, dead or alive, will shade foliage that wasn’t burned and those with some green remaining will continue to photosynthesis. Pruning forces new growth that will be damaged if there is another heat event and creates a place where diseases and pests can enter the plant. Also, keep in mind, if you cut back spring-blooming plants like rhododendrons, you’ll be cutting off buds that will be flowers next year. Foliage will grow back unless the plant is too far gone.
• Water deeply. Use drip or soaker hoses for more efficient water use; water is lost to evaporation when using an overhead sprinkler. Roots extend beyond the plant, so be sure to cover an area wider than just under the plant. Don’t overwater, however. Stressed plants are more susceptible to pests and diseases and root rot could become a problem. To test the moisture, stick a screwdriver in the soil. It will penetrate easily if the soil is moist. The best time is early morning so plants can use the water through the day when they need it and residual water will evaporate before night.
• Berries can be pruned lightly, but wait until the usual pruning time to remove this year’s fruiting canes.
• Apply mulch two to three inches deep. Any organic matter will help retain soil moisture and even out the temperature of the soil.
When the next drastic heatwave appears in the forecast, protect precious plants using a shade cloth, available at garden centers. Rig a frame and spread the cloth over. Try not to lay it directly on the plants so they have air circulation. The temperature under the shade cloth can be 10 degrees lower. Or, use shade cloth over cold frames, cloches and greenhouses. Avoid disturbing soil before and during heat waves as it will cause existing moisture to evaporate more quickly.