Bark, silhouettes and buds are the three keys to identifying trees in winter. My preference is buds, as they are so distinctly different from one species to the next. American basswood, or linden (Tilia americana), is a favorite. Its plump, oval, asymmetrical red buds, bearing only one or two bud scales are unmistakable.
One nice thing about having the ground covered with snow in October and November is that there is an additional tool available for tree identification. Like all flowering plants, trees have fruits which contain seeds. The fruits of many trees fall to the ground this time of year. They are very helpful identification tools, especially when they are so obvious against the white snow. In the photograph, there are fruits from five different trees: starting at the top and going clockwise is the fruit of the sugar maple (Acer saccharum), referred to as paired samaras by botanists. Each of the two seeds contains a papery wing that aids in dispersal. Next is the fruit of the white ash (Fraxinus americana), which has winged seeds borne in clusters. Eastern hophornbeam’s (Ostrya virginiana) fruit is a cluster of papery bladders, which usually separate upon dispersal. Each bladder contains a seed. Along the bottom is the fruit of American basswood or linden (Tilia americana) ; several round seeds are borne on a stalk which is attached to a single modified leaf. The last two clusters are the fruit of yellow birch (Betula alleghaniensis). They consist of structures that look like little bird feet (of which there are several in the photograph) that contain individual, tiny winged seeds (scattered throughout the photograph).