How to Tell if My Arborvitae is Dying
Learn to distinguish between normal seasonal browning, treatable plant stress, and the signs that your arborvitae's health is in serious decline.
Arborvitae are a popular choice for creating living privacy screens. When their green foliage turns brown, it can be difficult to distinguish between a temporary setback and a plant in serious decline. This guide will help you interpret the signs and understand what is happening with your plant.
Key Symptoms of a Dying Arborvitae
An indicator of an arborvitae in distress is the pattern of browning. Foliage that turns brown at the branch tips and slowly progresses inward toward the trunk signals a problem with water uptake. This pattern suggests the plant is struggling to move resources to its extremities. Healthy foliage should feel pliable and soft, but branches that are brittle and snap easily are likely dead or dying.
A change in foliage color beyond brown is another symptom. Needles that turn yellow or grayish can indicate underlying issues, with yellowing often being a first sign of overwatering. Widespread needle drop from the plant’s exterior is also a warning sign. While some interior needle loss is normal, losing needles from outer growth suggests the plant is under stress.
The problem may be localized, affecting only one section. This can happen if a portion of the root system is compromised, affecting the branches those roots supply. Entire branches turning brown and brittle while others remain green points to a sectional issue. Spotty, dead patches throughout the shrub also signal that the plant is struggling.
Understanding Normal Seasonal Browning
Not all browning on an arborvitae indicates a dying plant. A natural process known as “flagging,” or seasonal needle drop, is common in the fall. This occurs when the plant sheds its oldest foliage to conserve energy for new growth. You can identify this process by browning that happens only on the needles inside the plant, closest to the trunk.
This seasonal shedding is a healthy part of the arborvitae’s life cycle. The dense outer growth shades the inner branches, so the plant stops sending resources to this older foliage. These inner needles turn golden-brown and eventually fall off, leaving the green exterior intact. If browning is confined to the interior and the outer foliage remains healthy, it is likely seasonal needle drop.
Common Causes of Arborvitae Decline
Watering issues are a frequent reason for an arborvitae’s decline. Both overwatering and underwatering cause stress. Overwatering leads to waterlogged soil, suffocating the roots and causing root rot, a fungal disease. Underwatering, especially during hot periods, causes drought stress, preventing the plant from transporting moisture to its foliage.
For newly planted arborvitae, transplant shock is a common issue. During transplanting, a portion of the root system is lost, impairing the plant’s ability to absorb water and nutrients. This stress manifests as browning foliage as the reduced root system struggles to support the plant. It can take a full season or more for an arborvitae to establish a new, healthy root system and recover.
Winter burn is a challenge for evergreens. It occurs when foliage loses moisture to cold winds and sun while the frozen ground prevents roots from absorbing water. This desiccation causes needles to turn brown, usually on the side most exposed to wind and sun. Wrapping vulnerable plants in burlap can offer protection.
Pests and diseases can also be culprits.
- Bagworms create small, cocoon-like bags from the plant’s needles.
- Spider mites can cause a speckled, dusty appearance on foliage.
- Leafminers are insects that can damage foliage.
- Fungal diseases like canker create sunken lesions on branches.
- Root rot, caused by the Phytophthora fungus, is a soil-borne issue that can kill a plant.
How to Confirm if an Arborvitae is Dead
When you suspect a branch or the entire plant is dead, a “scratch test” can provide an answer. Using a fingernail or small pocketknife, gently scrape a tiny section of outer bark on a questionable branch. You only need to remove a small piece to see the cambium layer underneath. This test should be performed on the woody parts of the plant.
If the tissue beneath the bark is bright green, the branch is alive and has a chance to recover. A dull green color may indicate the plant is in poor health. If the tissue is brown, gray, or dry, that part of the plant is dead. Perform this test on several different branches to get a full picture of its health.
Start the test near the tip of a brown branch and work your way down toward the main trunk. If you find green tissue further down, you can prune the dead section just above the living part. If all branches appear dead, perform the scratch test on the main trunk near the base. Green tissue there means the root system is alive and may generate new growth.