Arborvitae Longevity, Hollow Trunks, and Carpenter Ants

Four 40-foot arborvitae, 24+ years old, lean toward the house. One has a hollow area where a branch was lost. Carpenter ants are present. Last year's drought killed 20-year-old azaleas. Owner fears removal is inevitable.

Hollow Doesn't Mean Dying

Living tissue is the outer sapwood and leaves. Hollow centers are normal in older trees. Hazard exists only if the tree could fall on a target.

Lifespan

Arborvitae (Thuja) species vary; in landscapes, 50 to several hundred years depending on conditions.

Carpenter Ants

Ants nest in decayed wood, not sound wood. They exploit existing decay from stress, injury, or drought. They don't kill trees.

• Treat nest cavity with Sevin or rotenone dust if desired.
• Do not seal cavities—traps moisture, worsens decay.

Leaning

Likely from decades of prevailing winds as a windbreak.

Recommendation

If foliage is green and full, keep them. Treat ants only if concerned. Replacement would take years to restore windbreak function.