How do I tell if a tree is dead?
Three checks draw on NC State Extension's gardener handbook: allow for the season, since deciduous trees drop all their leaves; scratch the outer surface of a small twig, where healthy wood showed green in its azalea case study; and watch for new growth, which the handbook says is when winter damage shows its full extent. Any one of them can mislead.
The season decides what a bare tree shows
NC State Extension's gardener handbook says deciduous plants drop all their leaves in a short period, while evergreens shed throughout the year, so a bare deciduous tree in winter is expected. Extension's pruning guide finds dead wood on deciduous trees easier to see in the growing season, which picking out a big dead limb applies to one limb.
After an extended drought, the pruning guide says to "wait until the following growing season to see what has died due to water stress," and the handbook says winter-damaged plants and branches that look dead "may still be alive."
The scratch test reads one twig at a time
In the scratch test from NC State Extension's gardener handbook, worked on an azalea, healthy branches are "white inside with green" when the outer surface of a twig is scratched, and its damaged branches died back at the tips, not to the base, the scratch showing where dead tissue met green.
A brown tip speaks for that tip, so a fair reading takes small twigs from several limbs, all within reach from the ground.
Dead-looking parts and a full leaf-out both mislead
Dead-looking parts turn up on living trees: NC State Extension says anthracnose, a group of fungal infections of hardwoods, can kill buds and shoots on hosts like sycamore, yet "these trees usually recover and produce more leaves by mid-summer." The NC Forest Service says declines "degrade tree health and eventually kill," often unnoticed until late, so a leafy tree can still be declining.
Someone at the tree settles whether it has died. A dead tree over a roof or a drive points the question at tree removal, and why dead wood changes the takedown sits with dead and rotten trunks.
Which checks came up dead, and on which limbs?
Questions people actually ask.
Can a tree leaf out late and still be alive?
Yes, in a case NC State Extension's gardener handbook describes: when a late freeze kills the leaf buds, the plant is often late to resume growth but eventually puts out new growth from dormant buds.
Can an evergreen stay green after it dies?
For a while: NC State Extension's gardener handbook says a cut Christmas tree tossed into the yard can stay green for several months, its example of how slowly stress shows on a living tree's leaves.
What does a stressed tree show from the ground?
NC State Extension's gardener handbook lists signs that woody plants are under duress, including leaf drop, especially on lower branches; new leaves smaller than normal; and branch or twig dieback.
Where can a twig go for a second opinion?
To the local county Extension center, where NC State Extension's gardener handbook sends samples and photographs to the Extension Master Gardeners, then to NC State's Plant Disease and Insect Clinic if the volunteers and county agent are unsure.