Douglas fir going yellow
I am not certain what is causing my mature douglas fir to suddenly go yellow in middle of branches but tips are not affected (yet). This has been quite rapid over two weeks. I do not use any chemicals in my yard so I know it's not round-up. I live in Port Orford adjacent to east end of Garrison Lake. I notice a tree on lake edge is also doing this same pattern of yellowing.
Curry County Oregon
Yellowing of older needles is not uncommon this time of year. Conifers like Douglas-fir are preparing for the winter by shedding their older foliage similar to how deciduous trees drop their leaves. If the amount of yellowing is abnormal, it is likely due to our ongoing drought. While the Coast hasn't been hit too hard, I have seen similar symptoms in Douglas-fir, especially in landscape settings where they tend to me a bit more stressed. As long as the tips remain green, it is likely that the trees will pull through assuming the drought lets up. If dry conditions persist into next summer, it may be beneficial to provide landscape trees with a few very deep waterings. Mulch around the base of the tree can also help give the tree more moisture but be careful not to add too much mulch at once as it can smother the fine roots.
Let me know if you have nay questions or if I can help further.