There are a couple of opportunities this weekend to learn more about trees:
Tree Essentials. On Sunday at Green Spring Gardens in Alexandria, Richard Murray is giving a class billed as "everything you always wanted to know about trees, but were afraid to ask." We went on a tree walk with him in December and it was really informative and well-pitched for people at many different levels. $10; registration required.
Flying squirrels spend almost all of their time in trees, gliding from one tree to another rather than running across the ground like their grey squirrel cousins. Several nature centers in the area are successful in getting them to come to feeders in the evening (they're nocturnal). This weekend, you can check them out at Long Branch on Saturday and Hidden Oaks on Sunday.
As always, there are lots of hikes and other activities on our calendar.