Trees make flower and leaf buds during warm weather when there is plenty of sun available for growth. These buds lie dormant during the winter (or dry months), then open in late winter and spring when stimulated by warmth, water, and/or increased day length.
Investigating winter twigs in the classroom offers a great opportunity for inquiry. For instance, have students observe, then draw and describe the different features and patterns they see.
Ask, What do you think each represents (e.g., a leaf scar)? How might you find out? How are the buds arranged? Can you tell which buds might produce leaves and which, flowers?
(Consider dissecting some buds with an Exacto knife and large pin.) How do buds from different kinds of twigs differ? How might we simulate spring to stimulate buds to burst? Consider having students go outside to see if they can find trees with twigs that match the ones they drew.