Why all the yellowing on Douglas firs?

Asked October 26, 2013, 3:55 PM EDT

We have 3 large Douglas firs on our property in West Salem. We are noticing yellowing of the needles. At this point the yellowing is affecting about 20% of the tree. I notice the same thing happening to neighbors trees on the same side of the street.

Polk County Oregon tree health douglas fir conifer disease

1 Response

Many people are submitting questions about browning of interior needles on their conifers, among them Doug firs. This is very common during late summer and fall, die to water stress (shortage) through our dry summer. This year the needle dieback is more severe than usual.

This response by a forester to a question similar to yours explains the situation: “There has been a lot of needle dieback and also branch, top, and even whole-tree dieback on Douglas-fir this last summer. A variety of issues, but almost all have the 2012 drought and the fairly dry summer of 2013 causing stress as one of the contributing factors. Now there is a good deal of needle dieback this fall. If it is limited to older, interior needles and the outer ranks of needles are healthy green, then it is probably just unusually heavy autumn shedding of needles (also likely related to the stressful climate last 2 years). I am seeing a lot of that, affecting some trees much more than others right nearby.”

If you would like to obtain a first-hand opinion about your Doug fir, I suggest you contact several Certified Arborists for an onsite evaluation. You can locate Certified Arborists in the Yellow Pages, online or in a phone book. Tree care companies with such a person will include that information in their ads, either as a brief statement or as a small rectangular logo stating “Certified Arborist.” We suggest Certified Arborists because they are trained in tree care, must pass an exam to acquire certification from the International Society of Arboriculture, and must accumulate mandated continuing education to retain certification. When you contact each company, avoid any unwelcome surprises by asking if they have a fee for the visit and evaluation.