---
title: "Why Your Arborvitae Has Brown Patches and How to Fix It"
canonical: "https://homegardeningblog.com/brown-patches-on-arborvitae/"
author: "Smith"
published: "2026-10-10T11:00:00+00:00"
modified: "2026-10-06T17:44:37+00:00"
language: "en-US"
site: "Home Gardening Blog"
description: "Brown patches on arborvitae usually mean one specific thing is going wrong. You just have to figure out what it is. The fix depends entirely on where the…"
categories: "Garden Care"
attribution: "Home Gardening Blog (https://homegardeningblog.com/)"
---

# Why Your Arborvitae Has Brown Patches and How to Fix It

Brown patches on arborvitae usually mean one specific thing is going wrong. You just have to figure out what it is. The fix depends entirely on where the damage sits and what time of year you are looking at it.

 

Arborvitae trees (Thuja species) need about one inch of water per week during dry spells to stay healthy. As of 2026, university extension programs still report winter desiccation as the top cause of evergreen browning in northern climates. Let's walk through exactly how to diagnose your tree and what to do next.

 

![brown patches on arborvitae](https://homegardeningblog.com/wp-content/uploads/2026/10/brown-patches-on-arborvitae-muwyfdj1.webp)

 

Image source: Bing (Web (fair-use with source credit))

 

## Quick Answer

 

Brown patches on arborvitae happen for a few reasons. Winter burn dries out the outer branch tips. Bagworms eat the green foliage from the inside out.

 

Root rot turns lower branches brown first. You must identify the exact pattern before treating the tree.

 

## The Hard Truth About Brown Arborvitae Patches

 

Here is the part nobody wants to hear. Dead brown tissue on an arborvitae will never turn green again. Evergreen conifers do not regenerate new needles over old dead wood like deciduous trees do.

 

If a branch is completely brown and brittle, that section is gone for good.

 

That does not mean your entire privacy screen is doomed. It means you have to act fast to save the living wood. Our research into plant pathology shows early diagnosis is the only reliable way to stop the spread.

 

Waiting until the whole hedge looks crispy guarantees you will be buying replacement trees.

 

The first step is always a physical inspection. Do this before you buy any sprays or fertilizers. Grab a pair of bypass pruners and look closely at the damaged areas.

 

You are trying to find the exact boundary between live green tissue and dead brown tissue.

 

Use the scratch test if you are unsure. Scrape a tiny sliver of bark off a questionable branch with your thumbnail. Green underneath means the cambium layer is alive and can push new growth.

 

Brown all the way down means that stem is dead.

 

You also need to know your specific cultivar. Thuja 'Green Giant' handles stress differently than Thuja 'Emerald Green'. Eastern arborvitae (Thuja occidentalis) is generally more prone to winter injury than Western redcedar (Thuja plicata).

 

Knowing what you planted changes the diagnostic path.

 

## Step 1: Pinpoint Where the Browning Is Happening

 

The location of the brown patches tells you almost everything. You need to step back and look at the whole tree first. Then get close and examine the specific damaged spots.

 

We use a simple spatial checklist to narrow down the cause quickly.

 

- **Outer branch tips only:** This points directly to environmental stress. Winter burn or salt damage usually scorches the exposed edges first.
- **Inner canopy near the trunk:** This is often perfectly normal. Seasonal needle drop happens every fall when the tree sheds older interior foliage to conserve energy.
- **Lower branches touching the ground:** Look for dog urine burns or Phytophthora root rot. Both start low and move up slowly.
- **One entire side of the tree:** Road salt drift or prevailing winter winds cause one-sided desiccation. The side facing the street or the north wind takes the hit.
- **Random scattered patches throughout:** This suggests pests like spider mites or arborvitae leafminers. They feed wherever they land without following a directional pattern.

 

![winter burn](https://homegardeningblog.com/wp-content/uploads/2026/10/winter-burn-muwyfeeo.webp)

 

Image source: Bing (Web (fair-use with source credit))

 

Pay attention to the height of the damage too. Pests rarely respect height limits. Environmental damage usually stops at the snow line or the splash zone from road traffic.

 

Fungal issues like Pestalotiopsis tip blight tend to cluster where air circulation is worst.

 

If the browning is strictly inside the tree and the outer tips are bright green, relax. That is natural seasonal shedding. Rake it out and move on.

 

But if the outer edges are crispy while the inside stays green, you have a real problem that needs action.

 

Document what you see. Take photos from three feet away and three inches away. You will need these details for the next step.

 

Matching the visual pattern to the biological cause is how we avoid wasting money on the wrong treatment.

 

## Step 2: Match the Pattern to the Real Cause

 

Once you know where the brown patches sit, you match them to the culprit. This is where most homeowners guess wrong. They spray fungicide on a bug problem or water a tree that is drowning.

 

Use this decision matrix to get it right.

 

| Symptom Pattern | Most Likely Cause | Time of Year | Confirming Detail |
| --- | --- | --- | --- |
| Outer tips brown, inner green | Winter burn (desiccation) | Late winter to early spring | Damage faces prevailing wind or road |
| Inner foliage drops, outer green | Natural seasonal needle drop | Fall (September to November) | Only oldest interior needles fall |
| Small holes in scales, sawdust | Arborvitae leafminer | Spring to summer | Hollowed out scale leaves |
| Webbing, dusty foliage | Spider mites | Hot dry summer months | Mites fall onto white paper when tapped |
| Cone-shaped bags hanging | Bagworms | Late spring to late summer | Bags contain silk and dead foliage |
| Lower branches dying upward | Root rot or dog urine | Anytime after heavy rain | Soil smells sour or ammonia is present |
| Spotty brown tips with black dots | Fungal blight | Humid wet summers | Tiny fruiting bodies visible under magnification |

 

Winter burn happens because the tree loses moisture through its leaves faster than frozen roots can replace it. The sun and wind pull water out. The roots cannot pump it back in.

 

That is why anti-desiccant sprays work best when applied in late November before the ground freezes solid.

 

Bagworms are sneaky. They build protective cases out of the tree's own foliage. By mid-summer, those cases are tough enough to block most contact insecticides.

 

University extension pest management programs recommend treating bagworms in June when the larvae are small and exposed. Spraying in August is mostly a waste of time.

 

![bagworms](https://homegardeningblog.com/wp-content/uploads/2026/10/bagworms-muwyfetl.webp)

 

Image source: Bing (Web (fair-use with source credit))

 

Spider mites require a different approach. They thrive in hot, dry, dusty conditions. Tap a suspect branch over a piece of white printer paper.

 

If tiny specks start crawling around, you have mites. Horticultural oil works well here. Heavy chemical miticides often kill the beneficial predatory mites that keep spider mite populations in check naturally.

 

Fungal blights love humidity. If your arborvitae are planted too close together, air cannot circulate. Moisture sits on the foliage overnight.

 

Copper-based fungicides can protect healthy tissue from spreading infections. They will not cure wood that is already dead. Pruning for airflow is just as critical as spraying.

 

Root rot is the silent killer. Arborvitae hate sitting in standing water. If you have heavy clay soil and water the tree daily, you are suffocating the shallow fibrous root system.

 

Cut back irrigation immediately. Let the top two inches of soil dry out completely before watering again.

 

## Step 3: Decide What to Do Based on Your Diagnosis

 

Now you have your answer. Here is the workflow for fixing it. Do not skip steps.

 

Rushing the repair causes more harm than the original problem.

 

**If the cause is winter burn:**

 

Wait until late spring. Do not prune brown tips in February. The dead foliage actually insulates the live buds underneath from further cold snaps.

 

Once new growth pushes in May or June, snip the dead tips back to the nearest green lateral bud. Water deeply during dry spells. Apply an anti-desiccant spray next November.

 

**If the cause is bagworms or leafminers:**

 

Handpick bagworm cases if the infestation is light. Drop them in soapy water. For heavy outbreaks, apply a targeted biological insecticide containing Bacillus thuringiensis kurstaki (Btk) in early June.

 

Timing is everything. Btk only works when caterpillars are actively feeding and small.

 

**If the cause is spider mites:**

 

Blast the foliage with a strong stream of water early in the morning. This physically knocks off mites and disrupts their webbing. Follow up with a dormant oil or horticultural oil application.

 

Avoid broad-spectrum insecticides. They wipe out natural predators and trigger worse mite flare-ups later.

 

**If the cause is fungal blight:**

 

Sanitize your pruning shears with rubbing alcohol between every single cut. This prevents dragging spores from sick wood to healthy wood. Remove infected branches back to healthy tissue.

 

Improve spacing if possible. Apply a registered copper fungicide according to the label directions during wet weather.

 

**If the cause is root rot or poor drainage:**

 

Stop watering. Pull mulch away from the trunk base. Mulch should be two to three inches deep but never touching the bark directly.

 

If the soil stays soggy for days after rain, you may need to amend the planting bed or install French drains. Severely rotted trees usually cannot be saved.

 

**If the cause is dog urine:**

 

Install a low physical barrier or train pets away from the foundation planting. Flush the affected lower branches with clean water immediately after exposure. There is no chemical cure for urine burn once the tissue dies.

 

You just have to protect the remaining live wood.

 

Always dispose of diseased or pest-infested clippings in the trash. Never put blighted arborvitae wood into your home compost pile. Most backyard compost bins do not reach temperatures high enough to kill persistent fungal spores or bagworm eggs.

 

## Common Mistakes That Kill Arborvitae Faster Than the Problem

 

We see the same errors repeatedly in aggregate landscaping reports. Good intentions ruin healthy hedges. Avoid these traps.

 

Panic pruning is the biggest one. Homeowners see brown patches and hack the tree back to bare wood. Remember the hard truth from earlier.

 

Bare wood on an arborvitae stays bare. Only prune back to live green foliage. Leave the ugly brown tips alone until you confirm they are truly dead.

 

Overwatering ranks second. People assume brown means thirsty. If the roots are drowning in clay soil, adding more water accelerates Phytophthora root rot.

 

Check the soil moisture with your finger before grabbing the hose. Wet soil plus brown leaves equals a drainage problem, not a drought problem.

 

Applying the wrong chemical is third. Spraying fungicide on bagworms does nothing. Drenching spider mites with systemic neonicotinoids harms pollinators without solving the mite issue.

 

Many municipalities now restrict neonicotinoid use due to environmental impact. Read the pest identification chart above before buying anything at the garden center.

 

Wrapping trees incorrectly in winter causes hidden damage. Tightly bound burlap traps moisture against the foliage. That creates a perfect greenhouse for fungal blight.

 

If you wrap arborvitae to prevent snow load breakage, leave the top open for ventilation. Keep the fabric slightly loose around the branches.

 

Planting too deep at installation sets the tree up for failure years later. The root flare must sit slightly above grade level. Burying the trunk invites collar rot.

 

If your established trees are declining slowly without obvious pests, dig carefully at the base to check the planting depth.

 

Finally, ignoring mechanical damage matters. String trimmers slice through the thin bark easily. They sever the vascular tissue right at the soil line.

 

Keep mulch rings wide enough so you never need to weed-whack near the trunk. One careless pass can girdle a ten-year-old tree.

 

## Frequently Asked Questions

 

### Will brown arborvitae branches turn green again?

 

No. Dead brown tissue on evergreen conifers never regenerates new needles. If the scratch test reveals brown wood underneath the bark, that specific branch is gone.

 

You can only encourage new growth from surviving live buds nearby.

 

### How do I tell winter burn from a disease?

 

Winter burn affects the outermost tips facing wind or sun. Fungal diseases usually create random spots or start deep inside the canopy. Environmental damage also follows a clear pattern tied to weather exposure.

 

Diseases spread unevenly regardless of wind direction.

 

### When should I prune dead patches off my arborvitae?

 

Wait until late spring after the threat of hard frost passes. Pruning too early exposes tender inner buds to more cold damage. Snip dead tips back to the nearest living green lateral bud.

 

Never cut into completely bare wood.

 

### Can overwatering cause brown patches?

 

Yes. Soggy soil suffocates shallow roots and triggers Phytophthora root rot. The lower branches turn brown first and the decline moves upward.

 

Check your soil drainage before adding more water to a struggling tree.

 

### What kills bagworms on arborvitae fast?

 

Biological sprays containing Bacillus thuringiensis kurstaki work best in early June. The caterpillars must be actively feeding and small for the treatment to succeed. Handpicking bags works well for light infestations.

 

Drop collected bags directly into soapy water.