Shoot Tip Dieback

When you look at your arborvitae or thuja in spring, browning at the shoot tips is often your first clue that something went wrong over winter. The dead tissue contrasts sharply with the green interior foliage, and if the problem recurs year after year, your plant gradually thins out. Multiple causes combine to trigger this dieback: frost cracking from freeze-thaw cycles, drought stress from winter winds that dessicate evergreen foliage, or fungi like Phomopsis and Kabatina that colonize weakened tips. Cold, wet springs following harsh winters create perfect conditions for secondary fungal infection.

What matters is that shoot tip dieback is preventable through site selection and cultural care. Plant arborvitae in well-draining soil and avoid waterlogged sites that stress roots and reduce cold hardiness. Space plants generously to ensure air movement around foliage, avoid evening watering and overhead irrigation, and remove debris from under plants to reduce humidity. If dieback appears, prune out dead tips to improve appearance and reduce fungal spore production; copper or mancozeb fungicides applied in spring during new growth offer limited help if environmental stress is the root cause, so focus first on eliminating the conditions that triggered the injury.