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The aftermath of a tree toppled by the ice storm devastating Silverton, Ore., in February 2021. (Becca Owen for The Xylom)

Silver Storm: Once-in-A-lifetime Ice Storm Wrecks Trees in “Oregon’s Garden City”


Each spring, the empress tree growing next to my house glows with purple flowers. A month later, the blooms make way for wide, green leaves that dangle over the roof. When summer temperatures reach the hundreds, the empress tree shades the house during the hottest part of the day. An empress tree is opportunistic and weedy; it grows large and fast without much input.


The empress tree's purple flowers. (Becca Owen for The Xylom)

On the night of February 12th, 2021, I heard a crack, then a whoosh, then a thump as one of its branches broke off and hit the house. I jumped up off the couch. My elderly dog moved out of the living room and into the bedroom, far away from that unnerving sound. We were in the midst of a historic ice storm, and my empress tree, its branches thick with ice, was breaking apart.


 

Oregon’s Willamette Valley is a verdant agricultural hub for berries, Christmas trees, hops, and hazelnuts. It’s a Mediterranean climate with dry summers and mild, wet winters. Forty miles (70 kilometers) southeast of Portland, nestled against the Cascade foothills, is the town of Silverton. Silverton boasted the late Stu Rasmussen, the first openly transgender mayor in the United States. Another beloved resident was Silverton Bobbie, a dog who got lost on his family’s road trip to Indiana yet somehow made his way home to Oregon several months later.


On Labor Day weekend, 2020, Silverton was in the crosshairs of two out-of-control wildfires. Under an evacuation warning, I packed my dog into my car and fled to a less dangerous part of the state. For weeks, smoke and ash choked the skies. Flames came to the edge of town. Six months later, it felt odd to be under the threat of ice.


Ice storms occur when frozen precipitation hits a warmer pocket of air as it falls towards the earth. The melted precipitation can refreeze upon impact if the ground temperatures are below freezing. This creates a glaze that covers everything with a heavy, slippery coating. Sleet is different from this type of freezing rain: the frozen precipitation refreezes before it hits the ground, but not upon contact with tree branches or powerlines. The US National Weather Service designates an ice storm as an ice accumulation of at least a quarter inch. During the Silverton ice storm, ice accumulated up to an inch and a half over all exposed surfaces.



The recipe for Portland, Oregon-area winter storms is when cold, dry air blows west through the Columbia River Gorge and mixes with the rainy, warm air over the Willamette Valley. This sort of clash can lead to a relatively rare snowstorm where an inch of snow can snarl traffic, cancel school, and cause residents to panic buy groceries. During this particular storm, Portland proper in the northern part of the valley had heavy snow, while the communities in the central region, which included Silverton and Salem, Oregon’s state capital, experienced freezing rain and accumulating ice. Another fifty miles (80 km) south in Eugene, temperatures stayed well above freezing.

All night, loud cracks echoed throughout the still, cold air. The neighbor’s maple was splitting apart, heavy ice-covered branches popping off. Powerlines buckled under the weight of heavy ice, too. “If you’re in the central Willamette Valley tonight,” the meteorologist on the news said, matter-of-factly, “you will lose power.”


An inch and a half of ice weighs down a tree’s branches and can fatally damage its canopy. It can also cause the tree to splinter or even topple under the weight. Eric Hammond, a Silverton resident and certified arborist, knew what was coming when his neighbor’s birch tree began shedding branches during the ice storm. “I knew it was going to break. I know birch trees.” He told his neighbor to move their car before the tree crushed it. The neighbors did so, only to have their car crushed by a different tree. Across the street, a massive Oregon white oak tree ripped out of the ground. An ancient giant, felled.


An array of green and blue flashes lit up the night and my dark living room like high-voltage northern lights—transformers exploded, ensuring we would be without power for days. Even the phone stopped working, as ice-laden trees collapsed onto cell towers.

Oregon white oaks can live up to 500 years and can grow up to 90 feet (27.5 meters) tall. They have thick trunks and massive branches. Silverton was built on the edge of an oak savanna; today, only several groves of these historic trees remain. The city is protective of its signature tree and prohibits residents to cut specimens over 30 inches in diameter without special permission, even on private property. During the ice storm, centuries-old oak trees fared poorly when weighed down with ice. These giants were also responsible for the majority of property damage when they crushed houses and crushed cars.