Arborvitae Shrubs Turning Brown

Seeing your arborvitae shrubs turning brown can be a real worry. These evergreens are supposed to stay green all year, so browning is a clear sign something is wrong. The good news is that many causes are fixable if you act quickly. This guide will help you figure out why it’s happening and what you can do about it.

Before you panic, know that a little browning isn’t always a disaster. Sometimes, it’s a natural part of the plant’s cycle. Other times, it’s a cry for help. The key is to look at the pattern and location of the browning. This will point you toward the most likely cause.

Common Causes of Browning and How to Diagnose Them

Let’s break down the usual suspects. Look at your shrubs closely and compare what you see to these descriptions.

Environmental Stress and Weather Damage

Arborvitae can be sensitive to their surroundings. Weather extremes are a common trigger for browning.

Winter Burn: This is very common. It happens when frozen ground prevents roots from taking up water, but winter sun and wind pull moisture from the needles. Look for browning on the south or southwest side of the plant, the side most exposed to sun and wind.
Drought Stress: Arborvitae need consistent moisture, especially when young or newly planted. Browning from drought often starts at the tips of the branches and works its way in. The soil will feel dry deep down.
Root Rot from Poor Drainage: Ironically, too much water is just as bad. If the shrubs are planted in heavy, soggy clay soil, the roots can suffocate and rot. This browning is often more generalized and may start on the lower, interior branches first.

Pest Infestations

Certain insects specifically target arborvitae. You’ll often need to look closely to spot them.

Spider Mites: These tiny pests suck sap from needles, causing stippling (tiny yellow dots) that turns into overall browning. Check for fine webbing on the branches, especially in hot, dry weather.
Bagworms: These caterpillars create distinctive cone-shaped bags that look like small pine cones hanging from the branches. They can defoliate and brown a shrub rapidly if left unchecked.
Arborvitae Leafminers: The larvae of this moth feed inside the tips of the branches, causing the tips to turn brown and die back in late spring or early summer.

Diseases

Fungal diseases can also be to blame, often thriving in wet, humid conditions.

Kabatina or Pestalotiopsis Tip Blight: These fungi cause individual branch tips, usually on the lower parts of the shrub, to turn brown and die back. You might see tiny black fruiting bodies on the dead scales.
Canker Diseases: More serious than tip blight, cankers cause sunken, discolored areas on the bark and can kill entire branches. The foliage on affected branches turns brown.

Step-by-Step Troubleshooting and Solutions

Now that you have some clues, follow these steps to identify and adress the problem.

Step 1: Inspect the Pattern

Walk around your shrubs and note exactly where the brown is.
Is it on one side or all over? Is it at the tips, the base, or the interior? Take a few pictures to help you track changes over time.

Step 2: Check the Soil and Roots

Dig down a few inches near the root zone. Is the soil bone dry or swampy wet? Gently examine a few small roots. Healthy roots are firm and white or light brown. Rotted roots are mushy, dark, and may smell bad.

Step 3: Look for Pests and Fungi

Shake a branch over a white piece of paper to check for spider mites. Look carefully for bagworms or mined branch tips. For disease, inspect dead branches for fungal signs.

Step 4: Apply the Correct Treatment

Based on your diagnosis, here’s what to do:

For Winter Burn or Drought: Water deeply during dry spells in late fall before the ground freezes and again in early spring. For existing damage, prune out dead branches in spring once new growth starts. Water consistently during the growing season.
For Root Rot: Improve drainage immediately. You may need to aerate the soil, add organic matter, or in severe cases, relocate the shrub to a better spot. Avoid overwatering.
For Spider Mites: Spray the shrubs with a strong jet of water to dislodge mites. For heavy infestations, use horticultural oil or insecticidal soap, making sure to cover the undersides of the foliage.
For Bagworms: The simplest method is to hand-pick and destroy the bags before mid-summer when the eggs inside hatch. For large shrubs, use a labeled insecticide in early summer.
For Tip Blight: Prune out and destroy all infected branch tips several inches back into healthy wood. Disinfect your pruners between cuts with a bleach solution. Improve air circulation around the plant.
For Canker: Prune out infected branches well below the cankered area. There is no cure, so prevention through good care and avoiding wounding the bark is key.

Prevention is the Best Medicine

Keeping your arborvitae healthy from the start is much easier than treating problems. Follow these tips to prevent browning.

Plant Correctly: Choose a site with well-draining soil and at least 6 hours of sun. Don’t plant them too deep; the root flare should be visible at the soil surface.
Water Wisely: Provide about an inch of water per week, either from rain or irrigation. Water deeply at the base, not on the foliage, to encourage deep roots and prevent disease.
Mulch Properly: Apply 2-3 inches of organic mulch (like wood chips) around the base, keeping it a few inches away from the trunk. This conserves moisture and regulates soil temperature.
Fertilize Lightly: Use a balanced, slow-release fertilizer in early spring. Over-fertilizing can cause rapid, weak growth that’s susceptible to pests.
Prune for Airflow: Thin out dense growth occasionally to allow air to move through the shrub, which helps prevent fungal diseases.

FAQ: Arborvitae Browning

Can a brown arborvitae come back to life?
It depends. If the roots are healthy and the brown is only on the outer needles (like from winter burn), new green growth can eventually cover it. If the branches and roots are dead and brittle, those parts will not recover and should be pruned out.

Should I cut the brown parts off my arborvitae?
Yes, but timing matters. For winter damage, wait until late spring to see where new growth emerges, then prune the dead material. For disease, prune infected branches immediately to prevent spread, disinfecting tools between cuts.

How often should I water my arborvitae?
There’s no single schedule. Water deeply when the top few inches of soil feel dry. This might be once a week in hot weather, or less often in cool, wet periods. Consistent moisture is more important than frequent light sprinklings.

What is the best fertilizer for arborvitae?
A simple, balanced granular fertilizer (like a 10-10-10) applied in early spring is usually sufficient. Always follow the label instructions to avoid over-feeding, which can harm the plant.

Why is my newly planted arborvitae turning brown?
New plants are very vulnerable to transplant shock, which often shows as browning. Ensure it’s getting enough water (the root ball can dry out fast) and that it wasn’t planted to deep. Protect it from strong winds while it establishes.

Dealing with arborvitae shrubs turning brown requires a bit of detective work, but it’s often a solvable problem. By carefully observing the symptoms, identifying the cause, and taking the right action, you can usually restore your shrubs health and get them back to their vibrant green selves. Remember, providing consistent care throughout the year is the most effective way to prevent these issues from starting in the first place.