Long-Term Weather Effects on Trees in Denver

emerald ash borer damage
Damage caused by an emerald ash borer

It’s difficult to fathom the long-term effects of weather on trees; however, severe weather can damage trees for years.

On November 10th, 2014, winter began in Denver. In a matter of hours, the weather changed from sunny and warm to cloudy and cold. At 8:00 a.m. on November 10th, the temperature in Metro Denver was about 60 degrees. By 11 p.m. that night, temperatures had dropped to 16 degrees. The sudden arrival of winter and cold temperatures that day is still causing massive die-offs of trees and widespread damage to the tree population in Denver.

According to Tamla Blunt, a Colorado State University tree specialist, tens of thousands of trees in the Denver area have died because of the sudden drop in temperatures on November 10th, 2014. To survive the cold temperatures of winter on the Front Range, most species of trees harden their inner cores to consolidate energy and make prevent themselves from freezing. The sudden temperature drop on that fateful day in November, preceded by unusually warm temperatures in early fall that year, caused many trees to be flash-frozen before they could harden their cores to prepare for the winter. Many of them didn’t show signs of damage until spring. According to some arborists and researchers, Denver trees could be battling the effects of November 10th, 2014 for years to come. In 2016, some trees remain damaged by the sudden change in weather.

Many of the trees that survived the flash-freeze still suffer from other problems. Because their inner cores were damaged their overall health. Thousands of the estimated 2.2 million trees in Denver have leaf fungi infections, tussock moths, and the emerald ash borer. This increase in insects and fungi has also resulted in damage to trees in neighboring towns, such as Boulder, Colorado. Researchers say that these and other common tree ailments could make a comeback amongst Denver tree species over the next few years and become the final blow for many trees damaged by the sudden freeze.

According to some studies, the overall cost of the November 2014 freeze could be around $10 million for the city of Denver before factoring in property devaluation, air quality, and other factors. Over time, that cost could rise. Signs of tree damage include peeling bark, a significant reduction in fruit or leaf production, dead limbs, or needles and leaves browning and falling off early in the season, and stunted growth. Experts say that regular pruning of dead branches, fertilization, and cutting back on water are as important as ever to help trees recover and prepare adequately for the winter.

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