We had a lot of rain in Boulder last month (you may have heard!). Shortly thereafter some of the leaves on my 2 oak trees started to yellow, sort of randomly around the trees. The first picture shows a closeup of the leaves on one of the trees (a pin oak), and the other picture shows the 2 trees together (the right is a burr oak). You can see the yellowing around the trees if you look closely. The pin oak has shown signs of chlorosis on a few lower branches, but the closeup is not one of those branches.
Normally the leaves turn a golden brown after a good frost and stay on the tree most of the winter. I am guessing that the trees have drowned or are drowning. My favorite arborist says he is "not sure" what gives. Do I need to take any action?
Many thanks! Matt
The picture of the yellow leaves actually looks like a northern red oak. regardless, it could have been caused by excess water. In the picture of the two trees they don't look too bad, but it is a little hard to tell because of the back lighting. The only way they would be affected by the flooding is if the root systems were flooded for many days. It would have to be standing water, or at least if you dug a hole it would fill with water. Even so, I suspect that the trees will be fine and will do OK next year. Normal fall leaf drop is happening now anyway.
Many thanks for the reply! It rained heavily for 4 days, and the water table rose to maybe 1 meter below grade, so it *was* the next thing to standing water, and the defoliation seemed early and irregular. I guess you recommend no activity, so we will wait till spring and see. Rgds, Matt