Many trees go dormant in the winter, meaning they stop growing and rest. Typically the leaves will change color and drop in the mid to late Fall and branches will remain bare for several months. A new flush of leaves and or flowers then generally begin to sprout out in the Spring.
Bare branches can also be beautiful, lending character and interest to a landscape.
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Photo 53182833 / Bare Branches © Anico G. Enderle | Dreamstime.com