They die after producing and scattering their seeds. Some plants take two years before their seeds mature, and these are known as biennials. Many plants live for more than two years. These are the perennials. 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.