Our Doug for trees are raining down pitch on cars and decks. It’s Fall is this normal
We live on acreage with hundreds of Doug Fir trees and they all seem to be misting down pitch every day that constantly needs to be washed off of cars and skylights. It’s late November and I don’t ever remember this happening before in the fall. I’m hoping the trees are healthy. Is this a normal occurrence?
Placer County California forestry
Douglas-fir and other conifers tend to pitch sap as a defensive mechanism. Typically when it is coming from the trunk it's an indicator of insects, fungi, or physical damage that the tree is defending itself against. In your case, it sounds like the sap is coming from up high. This could be the result of broken branches or other damage causing sap to pitch. However, new cones also tend to produce a lot of sap, which can drop down or get dispersed by the wind (see picture below). While this typically happens in the late spring/summer when the cones are "ripening", it's not unheard of to occur in the fall too. I recommend you look at the Doug-firs around the area where you're noticing the sap collect and keep an eye out for greenish cones or any kind of damage in the branches of the trees.
If you'd like, you can send some pictures of the trees in question and I'll see if I notice anything unusual.