Why can pine trees keep their green needles all winter while many other trees drop their leaves?
Show answer & explanation
Answer: Their narrow, waxy needles lose very little water in winter
Pine sap stays warm and keeps the needles from freezing — Tree sap doesn't produce heat; pine needles cool to the temperature of the air around them. They survive freezing because their cells pack in sugars that work like a natural antifreeze.
They grow a fresh set of needles every autumn — Pines don't replace all their needles each year; a needle usually stays on the tree for two to seven years. Old needles drop a few at a time, which is why the tree never looks bare.
Their narrow, waxy needles lose very little water in winter ✓ — Frozen ground works like a drought, because roots can't draw water from ice. Broad, thin leaves would dry the tree out, so many trees shed them, but pine needles are narrow, thickly waxed and have sunken pores, so they can stay on through winter.