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Arborvitae leaves turn brown for several common reasons that are easy to identify.
If you’ve noticed your arborvitae leaves turning brown, the issue usually comes down to water stress, pests, or environmental damage.
Brown arborvitae leaves can appear suddenly or over time, depending on what’s causing the problem.
In many cases, arborvitae leaves turning brown is a sign that your plant is struggling, but it’s often fixable once you know the cause.
This post will walk you through the most likely reasons your arborvitae leaves are turning brown and what you can do about it.
Let’s dive in.
Common Reasons Arborvitae Leaves Turn Brown
1. Underwatering or Drought Stress
When arborvitae don’t get enough water, their leaves turn brown from the tips inward.
This is one of the quickest ways you’ll see arborvitae leaves turning brown, especially during hot, dry spells.
The plant sacrifices its outer foliage to conserve moisture, and that foliage turns brown and crispy.
If you’ve been skimping on watering, that’s probably why your arborvitae leaves are turning brown.
2. Overwatering or Poor Drainage
Ironically, too much water also causes arborvitae leaves to turn brown.
Roots sitting in soggy soil can’t get oxygen, which leads to root rot.
Once the roots start dying, the leaves turn brown and wilt.
Overwatered arborvitae often have browning leaves that feel mushy rather than dry.
3. Winter Burn
Winter burn is a classic reason for arborvitae leaves turning brown in late winter or early spring.
Cold winds and bright sun dry out the foliage while the ground is frozen, so roots can’t replace lost water.
The result is brown, desiccated leaves on the side facing the wind or sun.
This type of browning often affects older foliage first and is more common in exposed locations.
4. Pest Infestations
Certain pests like spider mites, bagworms, and aphids can cause arborvitae leaves to turn brown.
Spider mites are tiny and leave fine webbing; bagworms create hanging bags and eat needles.
If you see browning patches combined with webbing or bags, pests are likely the culprit behind your arborvitae leaves turning brown.
5. Fungal Diseases
Fungal infections like tip blight or root rot can also turn arborvitae leaves brown.
These diseases often start at the tips or base and spread upward.
Wet, humid conditions make fungal problems worse, leading to extensive browning of arborvitae leaves.
How to Diagnose Why Your Arborvitae Leaves Are Turning Brown
Step 1: Check the Soil Moisture
Stick your finger two inches into the soil near the roots.
If it’s bone dry, underwatering is likely causing your arborvitae leaves to turn brown.
If it’s soaking wet and smells musty, overwatering or poor drainage is the problem.
Step 2: Examine the Pattern of Browning
If the browning is on one side or the top, it’s probably winter burn or wind damage.
If it’s spotty and scattered, pests or disease might be responsible.
Entire branches turning brown from the inside out suggests a root or trunk issue.
Step 3: Look for Pests and Webbing
Inspect the leaves and stems carefully, especially where you see browning.
Use a white piece of paper to tap branches over it and look for tiny moving specks (spider mites).
If you find bagworms, their cocoons look like small pine cones hanging from branches.
Step 4: Assess Recent Weather and Exposure
Think back to the past few months.
Did you have a harsh winter, a drought, or heavy rain?
Arborvitae leaves turning brown often trace back to a sudden weather shift.
How to Fix Arborvitae Leaves Turning Brown
1. Adjust Watering Routine
If underwatering is the cause, give your arborvitae a deep soak once a week during dry periods.
If overwatering is the issue, stop watering until the soil dries out, and improve drainage if needed.
Consistent moisture helps prevent more arborvitae leaves from turning brown.
2. Provide Winter Protection
Wrap your arborvitae in burlap or install a windbreak before winter to reduce winter burn.
Water deeply in late fall so roots have moisture stored before the ground freezes.
This stops future arborvitae leaves from turning brown due to cold drying winds.
3. Treat Pests Promptly
For spider mites, use a strong spray of water or insecticidal soap.
For bagworms, handpick the bags and destroy them.
For severe infestations, consider a horticultural oil or appropriate pesticide.
Acting fast stops more arborvitae leaves from turning brown.
4. Prune Affected Branches
Cut off any branches that are completely brown and dead.
This improves air circulation and reduces the chance of disease spread.
Don’t cut into the green wood if you can help it, as arborvitae don’t regrow from old wood easily.
5. Apply Fungicide if Needed
If a fungal disease is causing arborvitae leaves to turn brown, apply a copper-based fungicide according to label instructions.
Also remove fallen debris around the base to reduce spore spread.
So, Why Are My Arborvitae Leaves Turning Brown?
Your arborvitae leaves are turning brown for one or more of the common reasons we covered.
Water stress, winter burn, pests, and diseases are the usual suspects behind arborvitae leaves turning brown.
The good news is that most causes are manageable with proper care and timely action.
Start by checking soil moisture, looking for pests, and evaluating your plant’s exposure.
Once you know why your arborvitae leaves are turning brown, you can take the right steps to revive your plant and prevent future browning.
Your arborvitae will thank you with healthy, green foliage.