Clusters of oak leaves fallen
1) For the past several weeks there are large numbers of oak leaf clusters on the ground under my mature white oaks. Most are dry, but fresh ones come down every day. The canopy has thinned. In the past I thought it might be from squirrel nests, but that would usually be earlier in the spring. One of these oaks was affected by a blight last year (something like jumping oak gall, which you identified for me). I would hate to lose these beautiful trees, but they do not look happy. 2) The white oak that had the gall last fall has at its base a small garden. Now it is mostly poison ivy, also vining up the tree. I would like to get rid of the PI once and for all, but how to do that without hurting the tree, already vulnerable. There are some nice flowers (Astilbe, Columbine) and a small holly in the garden, but I would sacrifice them if necessary to do away with the PI. Please advise, and thank you so much!!
Baltimore County Maryland
1. This is probably squirrel work. They don't necessarily do it for nesting. Hence the term "squirrelly." There is nothing you can do about it. In a healthy tree it would have no impact, as trees put out more leaves than they actually need for just such occurrences.
Old oaks are declining throughout the state and region for many reasons, one of which is changing climate, but also age. A home landscape is not the ideal one for trees, as our mowing compacts the soil and we don't allow the trees' leaves to decompose where they fall and feed the tree and improve the soil. Try to mow as many leaves as possible and let them lie. Never mow when soil is wet.
2. Read our page on handling poison ivy: https://extension.umd.edu/hgic/topics/poison-ivy
As like when getting rid of any vine (such as invasive English ivy), use a shield of cardboard or plastic when you spray an herbicide (especially those with the ingredients of glyphosate or triclopyr) between the vine and your desirable plants, including tree bark. For vines going up a tree, cut at the base and again at shoulder height, remove. Immediately spray the vine stump with the herbicides above.
With poison ivy, it's mainly a matter of being thorough. Then, we alert for new plants because birds drop the berries under trees and new little plants will start occasionally.