There are several ways to tell, and a little detective work can determine whether the woody plant is dead and we should consider replacement, or if there’s life and we need patience.
First, bend twigs gently. Dead twigs are usually brittle, and snap when bent. Live twigs are pliable and bend without breaking.
Second, and most reliable is the “scratch test.” With your thumbnail or a knife, gently scape a small part of the outer gray-brown bark from a twig or branch. Directly inside the outer bark on healthy trees/shrubs you’ll find a nice green layer, called the cambium. That’s were the growth of the plant occurs. If you continue scratching away the thin green layer, you’ll see the whitish inner wood. The presence of the green layer indicates life in the twig or branch. Sample wood from around the tree or shrub to determine whether the entire plant is healthy.
On the other hand, if the scratch test reveals that the layer beneath the outer bark is brown, without the presence of a green layer, that twig or branch portion is dead. Continue checking around the tree or shrub to determine if the entire plant is dead, or just portions. Follow up by bending twigs to see if they snap, giving a second opinion of death.
If the above-ground portion of a deciduous (leafy) shrub is injured, the shrub usually regrows from the base after pruning back. But if the entire above-ground portion of a tree is injured, the tree is often best removed, even if sprouts emerge from the base.
If in doubt, be patient to see what spring and early summer brings. Happy Gardening!