Record heat wave damages plants and trees across Oregon

Melanie Henshaw
(Aviana Dimanche/Unsplash)

(EUGENE, Ore.) The unprecedented, record-breaking heat wave that hit Oregon in June damaged trees and plants across the state, concerning local gardeners and plant lovers. Experts say the damage is real, but many plants will survive despite the damage.

According to the National Weather Service, between June 25 and June 28, temperatures across the state soared past 100 degrees, breaking multiple records. In Portland, temperatures reached 115 degrees, and the hottest places in the state, Marion and Gilliam counties, reached 117 degrees.

The heat wave had devastating effects on Oregonians. At least 116 people throughout the state died, prompting the state to declare a mass casualty event.

The temperatures also worsened the drought plaguing the entire state, and damaged many crops. According to Oregon Public Broadcasting, some Christmas tree farmers lost up to 90% of their crops, and cane berry farmers also suffered heavy losses. 

Most plants typically thrive in moderate temperatures between 50 and 90 degrees. Many plants can tolerate heat up to 100 degrees for short periods of time, but sustained temperatures higher than 100 degrees pose a risk to most species. 

Even plants that typically thrive in hot summer temperatures can be damaged by excessive warmth. Tomatoes, peppers, squash and melons are heat-loving plants, but suffer in extreme temperatures. When exposed to temperatures over 95 degrees for long periods, many halt all growth and the flowering process. 

At high temperatures, plants can begin to show signs of heat stress. Symptoms of heat stress include leaf curling, scorching, browning and wilting. 

Several days of temperatures well above 110 degrees in many parts of Oregon caused severe damage to plants, scorching forests, killing gardens and crops and statewide. 

The Oregon State University Extension Service Master Gardeners program says it was inundated with questions from gardeners about how the heat affected gardens. 

The heat wave in June was also unusual in its timing, as August is typically the hottest month in Oregon, particularly for the Willamette Valley. 

Climate change continues to drive temperatures upward in the American west. According to the Oregon Climate Change Research Institute’s Fifth Oregon Climate Assessment, which examines the likely effects of climate change on the state. Released this January, the report states that the frequency and magnitude of extremely hot days are increasing.

This August is predicted to be hotter than average. 

According to the OSU Extension, gardeners can attempt to mitigate the negative effects of further extreme heat on plants using several methods.

Watering early in the day or late in the evening when temperatures are cooler can help plants in extreme heat. Watering plants deeply, using shade cloth to protect plants from the direct sun and applying mulch to the soil to maintain an even ground are all ways to normally protect vegetation from extreme heat.

However, at extreme temperatures like Oregon saw last month, these methods may not be totally effective. 

The Extension advises gardeners to resist extensive pruning of damaged plants. The remaining foliage, even if brown, can help protect the plant from further damage.

Plants and trees beyond the home garden also suffered from the heat damaging Oregon’s forests.

Lauren Grand, an OSU Extension forestry agent for Lane County and assistant professor of practice in forestry at OSU, said the damage to forests after last month’s heatwave is unlike anything the Extension has dealt with before. 

“This is a new phenomenon. We haven’t had a situation like this in the recent past. We don’t know what the long-term effects are going to be,” said Grand. 

Trees in forests across Western Oregon were scorched. The sun and high heat damaged the needles and stems of trees, causing them to brown and fall off. Grand asserts this damage can cause a lot of trees to die, more than is typical in the summer. 

“We’re inferring there is continued stress occurring on trees over many years of drought, and an inability to fully recover each year,” said Grand. “Because of the increased damage to the tree’s tissues, it can’t photosynthesize as easily or as readily, overall weakening the tree and leaving it more susceptible to insects and disease [that] it would normally be able to fight off.”

Grand stated the heat can decrease the overall moisture in the soil, and the damage to a large area can leave it more susceptible to fire. Dry needles and low moisture across a large area of trees would allow a fire to spread more easily. This poses a concern due to this fire season’s grim forecast, with major wildfires already burning across Oregon. 

“In terms of recovery, people who have begun to replant in burn areas, the high heat and drier conditions have taken a toll on the efforts. I’ve heard from organizations helping landowners replant, the seedlings did not make it. Newly planted trees and plants are very sensitive,” Grand said.

Young tree saplings can really benefit from a shade structure, which could help in the event of another heatwave. 

Although the long-term effects of the heat damages to Oregon’s forests are unclear, researchers are examining the issue, Grand concluded. 

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Multimedia journalist passionate about covering issues regarding the environment and Indigenous rights, and food. Always searching for the next great meal.

Eugene, OR

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