May 10, 2013
Some Douglas-firs and other conifers in northwestern Oregon look noticeably haggard this spring, and concerned residents are asking why. As with most events in the long life of trees, the cause goes back a ways – in this instance, to last summer and fall.
“My best explanation is drought stress,” said Brad Withrow-Robinson. “We had a pretty hard end of summer last year - No rain until mid-October - then, boom! It was winter.”
The Oregon State University Extension forester explained that the lack of water stressed the trees. But because the dry conditions occurred late in the growing season, the effects didn’t show up until now. People are seeing dead treetops and flared-out branches – classic signs of drought stress.
The recent warmer-than-average weather “seems to have made it more sudden and dramatic,” he said.
While the Willamette Valley is idyllic for people, it can be a challenging environment for trees.
“Many of our soils in the valley are poorly drained, which is hard on most of our conifers, and other soils are fairly shallow and cannot hold much water,” he said. “Also, our summers are hotter and drier than in the mountains.”
These stressors lower trees’ resistance to disease and pests.