Why Is My Arborvitae Turning Brown?

Browning arborvitae are the most common question some extension offices get. Brunswick County Extension in North Carolina says so outright. The good news is that a lot of it is normal. The bad news is that the rest has several possible causes that can look alike at first.

What helps most is reading the pattern. Where on the plant is the brown? When did it appear? Is it one plant or the whole row?

Quick diagnosis chart

Below, each one in more detail.

1. Normal fall needle drop

Every fall, arborvitae shed their oldest foliage. These are the scale-like sprays on the inside of the plant, closest to the trunk. They turn yellow, then brown, then drop.

Iowa State Extension explains that evergreens shed their oldest, innermost needles in fall and that this is probably not a problem. Missouri Extension says the same, and Brunswick County Extension adds that it’s not usually serious as long as the outer growth stays green. A University of Maryland Extension expert gave the same answer to a homeowner whose three-year-old Green Giants browned on the inside in early November.

How to tell: brown is on the inside, the outer foliage is green and healthy, and it’s fall.

What to do: nothing, except clean up. NC State’s Henderson County office recommends clearing the dead needles out of the interior at least once a year, because piles of them hold moisture against stems and can lead to canker. A good shake or a gloved hand works.

One caution from Iowa State: drought and other stress can make the fall drop heavier than usual. If it looks like more than normal, check the soil moisture too.

2. Winter burn

This is the classic spring complaint. Arborvitae keep losing water through their foliage all winter. When the ground is frozen, roots can’t replace it, so the foliage dries out and browns. Minnesota Extension lists arborvitae among the most susceptible evergreens, and says new transplants are especially sensitive.

How to tell: Minnesota’s diagnostic page says winter injury shows up in late winter or early spring, starting at the tips with the base often still green. It’s worst at the top and on the side exposed to wind, sun or light reflected from buildings. Branches that were buried under snow stay green, which is a useful clue.

What to do now: be patient. Minnesota says the brown foliage is likely dead, but buds may still push new growth and fill in. Wait until mid-spring to prune, then cut back only to living tissue.

Preventing it next year:

• Water well all season, ease off slightly in September, then water thoroughly in October until the ground freezes. Minnesota says watering only in late fall doesn’t help much.
• Put up a burlap screen on the south, southwest and windward sides, leaving the top open.
• Skip anti-desiccant sprays. Minnesota Extension found them ineffective.
• Plant a variety known for holding color, like Emerald Green or North Pole. Monrovia lists North Pole as resistant to winter burn.

Salt injury (looks similar)

De-icing salt causes a similar pattern but on the side facing the road, driveway or sidewalk. Minnesota’s diagnostic page says the foliage browns from the tips down on that side, and growth slows with repeated exposure. Use the least salt you can, shovel before salting, and burlap the side facing the road.

3. Drought

Arborvitae have shallow roots and react badly to dry soil. The tricky part is timing. Oregon State Extension says drought damage may not show until fall, and Missouri Extension notes that spring browning can trace back to drought the previous fall. Wisconsin Extension says evergreens that go into winter dry can burn badly by spring.

Nebraska Extension reported that a dry, windy winter in 2021 to 2022 killed many evergreens, arborvitae among them.

How to tell: browning across the plant, not just on one side, often after a dry stretch. Push a screwdriver into the soil near the root ball. If it’s hard and dry a few inches down, you’ve found your answer.

What to do:

• Water deeply and slowly. Nebraska suggests about 1 inch per week in a single application when there’s no rain. A soaker hose under the mulch does this well.
• Oregon State says even established arborvitae need a deep soak every 2 to 3 weeks during dry spells.
• Keep 2 to 4 inches of mulch over the root zone, pulled back from the trunk.
• Don’t fertilize a drought-stressed plant. Nebraska and UConn both warn against it.
• Water in winter during thaws if the ground isn’t frozen and the fall was dry.

Your lawn sprinkler schedule is probably not enough for the hedge. The lawn watering guide is built for grass, which needs frequent shallow water. Arborvitae need less frequent, deeper soaks.

4. Transplant stress

New arborvitae arrive with a small root ball and no roots in your soil yet. In the first year or two they dry out much faster than established plants.

How to tell: the plant is new (under two or three seasons in the ground), and browning or thinning appears even without obvious drought. Often one or two plants in a new row struggle while others are fine.

Common causes:

• Not enough water. Minnesota Extension recommends daily water for two weeks, every 2 to 3 days through week 12, then weekly.
• Planted too deep. The top of the root ball should sit 1 to 2 inches above grade.
• Burlap, wire or twine left around the top of the ball.
• Circling roots from the pot never loosened.
• Heavily amended backfill that holds water like a bucket in clay soil.

What to do: check the soil moisture at the root ball itself, not just the surrounding soil. Root balls can be bone dry while the soil around them is damp. Water directly over the ball. If the plant was set too deep, it may be worth lifting and replanting while it’s still small. My arborvitae care guide walks through planting depth and a full watering schedule.

5. Bagworms

Bagworms are caterpillars that build bags out of silk and bits of the plant they’re eating. On arborvitae the bags look like small brown pine cones, which is why people miss them. Brunswick County Extension notes they’re often mistaken for the tree’s own seed structures.

How to tell: brown, chewed patches with no clear pattern, and spindle-shaped bags hanging from the twigs. University of Maryland Extension says newly hatched caterpillars make bags about 1/8 inch long, and by August or early September the bags are 1 to 2 inches.

Why it matters: Maryland says heavy infestations can permanently damage evergreens, and Ohio State says heavy defoliation can kill an arborvitae the following season. Damage often goes unnoticed until August.

What to do:

• Fall, winter or early spring: pick the bags off by hand. Each one can hold hundreds of eggs. Maryland says to get them off before the new generation hatches in May or early June. Bag them and put them in the trash, not on the ground under the plant.
• Cut, don’t pull. Brunswick County Extension says to cut the silk band with a knife or razor. Ohio State notes that bands left on can girdle branches years later.
• Late spring to midsummer: young caterpillars can be treated. Maryland says Bt works only on young bagworms and must go on by mid-July. Ohio State suggests applying it after hatching finishes, around the end of June in Ohio. Follow the product label.
• Late summer: sprays don’t do much on large caterpillars, according to Brunswick County Extension. Hand-pick instead.

6. Spider mites

Spruce spider mites are tiny and easy to miss. Penn State Extension lists arborvitae as a main host and calls it a cool-season pest, most active in spring and fall. NC State’s Henderson County office adds that mites are more likely on plants in high heat, like the southwest side of a building. Missouri Extension also notes that damage on the south or west side points to mites.

How to tell: Penn State describes speckled, yellowish foliage that loses its rich green, turning rusty with longer feeding. Damage usually starts on older foliage in the lower and inner canopy and spreads. Look for fine silk webbing. Oregon State mentions a grayish cast.

Paper test: hold a white sheet of paper under a branch and strike the branch hard. Watch for tiny dark specks that move. Penn State suggests checking three or four spots around the plant.

What to do: Penn State says the best treatment windows are early to mid-May, with a second round in early September if needed. If mite numbers are high, use a miticide that lists arborvitae and mites on the label and follow the label. They also warn that some general insecticides can make mite problems worse by killing their predators.

7. Dogs

Dog urine damages the lower foliage of evergreens, and arborvitae in a front yard or along a walking route are an easy target.

How to tell: browning at the base, on the bottom 1 to 2 feet, on one or two plants near a corner, path or mailbox. The brown sometimes looks dark or almost black.

I couldn’t find a university extension page on dog urine and arborvitae specifically, so take this section as practical advice rather than research. A Kentucky Living gardening column recommends keeping the dog from returning to the same spot, rinsing the soil with water soon after, and using a low barrier or border.

What to do: keep dogs off the hedge. A short decorative fence along the front of the bed works for neighborhood dogs. If it’s your own dog, train a different spot. Brown foliage won’t turn green again, so cut it back to green growth in spring and see whether new growth fills in. Lawn spots from dogs are a separate problem; my guide to fixing bare spots covers those.

8. Root problems

When roots fail, the whole plant shows it. Root rot is the most serious cause on this list because it’s usually not fixable.

Root rot. Oregon State’s plant disease handbook says many root-rot samples come from wet, poorly drained sites where roots lack oxygen. It rates ‘Smaragd’ (Emerald Green) as the most susceptible of the arborvitae it compared. NC State lists root rot in poor drainage as a Green Giant problem too.

How to tell: the whole plant dulls and browns, often in the wettest part of the yard or near a downspout. Penn State describes reddish-brown roots and discolored wood at the soil line in severe cases. Healthy roots are white or tan and firm.

What to do: Penn State says no chemical cures an infected plant and fungicides mostly prevent infection rather than kill it. Remove the dead plant. Before replanting, fix the drainage or choose a different spot, because Penn State also advises against replanting where infected plants grew. Oregon State says to find the cause before you replace anything.

Other root damage. Trenching, new construction, a new patio over the root zone or soil piled up against the trunk can all brown a plant from the roots up.

Crowding and shade

Lower branches that brown between plants in a tight row are often from shading and rubbing. Walter Reeves notes that when branch tips tangle with neighbors, they die and the lower limbs brown. NC State’s Henderson County office linked dense, shaded plantings to wet bark and canker. If you’re planting a new row, my guide to arborvitae spacing covers distances by variety.

Will brown arborvitae turn green again?

No. Brown foliage is dead foliage. What can happen is new growth from buds nearby. Minnesota Extension says buds may push growth and fill in bare areas after winter burn.

The catch is that arborvitae won’t grow new shoots from bare, old wood. Oregon State and UMass both say it. So a branch that’s brown all the way back to the trunk won’t fill in. A branch with green tips and a brown section further in might, slowly.

When to cut it back

Wait until mid-spring, after new growth starts. That way you can see what’s alive. Cut back to green growth or to a healthy side branch. Dead, broken or diseased branches can come off any time of year.

If a plant is more than half brown and nothing greens up by early summer, it’s usually time to replace it. Buy the largest replacement you can so it catches up with the rest of the row.

When to call someone

Get help if you can’t find the cause, if browning spreads plant to plant down a row, or if you suspect root rot. Your county extension office can often identify samples, and Brunswick County Extension notes that root rots, mites, scale and cankers often need a microscope to confirm. For tall trees, hire an arborist rather than working from a ladder.