Trees have special cells that monitor the light-to-dark ratio. When sufficient light is detected, the light receptors will tell the tree to start growing. The tree knows it spring because the days are getting longer.

Unpredictable spring weather can cause trees to start growing before the last frost. When the unexpected frost hits the new growth will die back. Spring dieback as a result of a late frost will cost the tree valuable energy, but as long as the tree is healthy it will likely survive and push out more new growth.