Buds ready to burst forth on a deciduous magnolia on the north side of the W&OD bike path east of Old Reston Avenue. This is probably either a Japanese magnolia (Magnolia liliiflora) or its hybrid, the saucer magnolia (Magnolia x soulangeana), for which see this Virginia Tech fact sheet.
On the north side of the W&OD bike path, midway between American Dream Way and Isaac Newton Square, one can find a number of these tall bushes that are now bearing a profusion of catkins. I don't know what this might be, though it quite well could be a member of the birch family, perhaps eastern hophornbeam.
Dried fruit husks on a sumac (Rhus spp.) on the south side of the W&OD bike path west of Isaac Newton Square. For a view of sumacs in fruit last fall, see this post.
Dogbane (Apocynum spp.), with its characteristic tuning-fork-like seed pods, in the clump on the south side of the W&OD bike path just east of Wiehle Avenue that was also featured in this post. Most of the seed pods are still closed and dried up; only a few have opened (note the much lighter-colored leaf-like structures in the upper center of the image; these are seed pods that have split open).