Can you even do botany in the winter? There are no flowers or leaves to distinguish plants and most things are covered in snow!
This is true, but winter gives us a chance to look more closely at the foundations of plants and trees without the distractions of color or camouflage of green. The bare branches of trees define their overall shape and stature clearly, and many may be known just by this. Other shrubs and trees can be identified by their branching patterns, bud shapes and placement, stem colours etc., and even herbaceous plants have parts that show through the winter and help us figure out their names (e.g. seed pods, bracts, spines).
There are guidebooks and keys specifically for winter botany, and the internet hosts a lot of great sites describing the tricks and techniques for identifying plants in the winter, just search for “winter botany”. Here are several books we have in the Herbarium, with a page from one that would help with the birches in the photo above!