Trees are the most visible members of this group. Some plants are sensitive to changes in temperature. They relax and unfurl when it's warmer. Many guide books include tiny silhouettes to help you identify the trees. The bark also differs considerably from tree to tree, and from young to old.
Buds offer many clues, too.
Before trees even lose their leaves in autumn, they are preparing for the new leaves that will clothe them the following spring. Each bud is protected by a scaled covering, or fuzzy hairs. There is much variation from tree to tree. Some trees are easy to identify any time of year. These are the evergreens that keep their leaves year-round.