Why Is My Leyland Cypress Turning Brown? An East Tennessee Guide

Drive through any subdivision in West Knoxville, Farragut, or Maryville and you'll see them: long green walls of Leyland cypress, the most-planted privacy screen tree in East Tennessee. They're popular for one reason — speed. A Leyland can put on three to four feet a year and build a living fence in five seasons. But that speed comes with a catch. Leylands are shallow-rooted, disease-prone, and frequently planted too close together in our heavy clay soil — and sooner or later, most homeowners watch one (or a whole row) start turning brown. Sometimes it's harmless. Sometimes it's a death sentence for the tree. This guide walks you through the five causes of Leyland cypress browning we see around Knox County, how to tell them apart, which ones are treatable, and when removal is the only safe answer.

1. Seiridium Canker — The #1 Leyland Cypress Killer

If individual branches on your Leyland are turning rust-brown while the rest of the tree stays green — a symptom arborists call flagging — the most likely culprit is seiridium canker, a fungal disease that experts at Clemson's Home & Garden Information Center rank as the most serious problem on Leyland cypress across the Southeast.

How to identify it: Look where a flagging branch meets healthy wood. You'll find a sunken, dark, slightly cracked patch of bark — the canker — often glistening with oozing resin that runs down the limb. The fungus enters through wounds and drought-stress cracks, then slowly girdles the branch, cutting off water until everything beyond the canker dies. Stressed trees are infected first, which is why outbreaks here tend to follow hot, dry East Tennessee summers.

Is it treatable? Partially. There is no fungicide that cures seiridium canker. The only management is pruning infected branches well below each canker, disinfecting tools between cuts, and reducing drought stress with deep watering and mulch. The University of Tennessee Extension, whose plant disease publications cover Leyland cypress problems for Tennessee growers, emphasizes prevention — proper spacing and watering — because once the disease takes hold, options shrink fast.

When the tree can't be saved: Once cankers appear on the main trunk, or more than half the canopy has flagged, the tree is effectively girdled and will not recover. At that point it's a removal, not a treatment, decision.

2. Bagworms — The Hidden Defoliators

That “pine cone” hanging on your Leyland in July? Look closer. Bagworms build spindle-shaped bags one to two inches long, camouflaged with bits of the tree's own foliage, and each bag hides a caterpillar that eats needles from June through August. A heavy infestation can strip whole sections of a tree in a single summer — and a single overlooked bag can hold hundreds of eggs that hatch the following spring.

How to identify it: Browning that starts patchy and thin, often near the top, with small cone-like bags dangling from twigs. Shake a branch — the bags don't fall like real cones.

Is it treatable? Yes — bagworms are the most fixable problem on this list. Hand-pick and destroy bags from fall through early spring before eggs hatch. During the active season, biological sprays like Bt (Bacillus thuringiensis) are effective on young caterpillars in late May and June.

When the tree can't be saved: Here's the part many homeowners don't realize: conifers do not releaf the way maples and oaks do. If bagworms strip a branch bare, that branch stays bare. Two or three years of severe defoliation can kill a Leyland outright, and a mostly-bare tree won't ever look like a privacy screen again.

3. Phytophthora Root Rot — The Clay Soil Problem

Knox County's red clay holds water like a bowl, and Leyland cypress roots hate wet feet. In poorly drained spots — low corners of the yard, downspout outlets, compacted new-construction soil — the soilborne water mold Phytophthora attacks the roots, and the tree begins dying from the bottom up: lower branches fade from dull green to yellow to brown while the top hangs on.

How to identify it: Bottom-up decline, overall thinning, and a tree that browns fastest in the wettest part of the row. Peel back bark at the base and the tissue underneath is often reddish-brown instead of healthy white.

Is it treatable? Realistically, no. By the time symptoms show in the canopy, the root system is already badly damaged, and no spray reverses rotted roots. Improving drainage may protect neighboring trees, but the infected one rarely recovers.

When the tree can't be saved: A root-rotted Leyland is doubly dangerous — the canopy dies and the anchoring roots decay, which is exactly the failure pattern we cover in our storm damage and hazard tree guide. Plan on removal once bottom-up browning passes the halfway point.

4. Drought Stress & Winter Desiccation

Leylands have shallow root systems for their size, and Knoxville sits in USDA hardiness zone 7, where summers regularly bring multi-week dry spells. A drought-stressed Leyland browns from the inside out and top down, often on the sunniest, windiest side first. Winter adds a second insult: winter desiccation, where cold winds pull moisture out of the evergreen foliage faster than frozen roots can replace it, leaving scorched, bronze-brown patches by February.

Is it treatable? Usually, if you act early. Deep-soak the root zone weekly during dry stretches (a slow trickle for an hour beats daily sprinkles), spread two to three inches of mulch out to the drip line, and water thoroughly in late fall before the ground freezes. Mildly scorched trees often green back up from buds that survived.

When the tree can't be saved: If entire limbs are crispy — needles that crumble in your hand and twigs that snap with no green underneath — those limbs are dead. And remember the chain reaction: drought stress is the open door seiridium canker walks through. A badly drought-burned Leyland that then develops cankers is usually on a one-way slide.

5. Natural Needle Shed — The Harmless One

Not all browning is bad news. Every fall, Leyland cypress (like all conifers) sheds its oldest interior needles — the ones closest to the trunk that no longer get light. If the browning is only on inner foliage, evenly spread through the tree, with healthy green growth at every branch tip, that's normal seasonal shed, not disease.

The test: location, location, location. Inner browning with green tips = relax. Browning at the tips, whole flagged branches, or bottom-up decline = one of the four problems above. If you're not sure which pattern you're looking at, our guide to the signs a tree is dying walks through the same checks for any species — or just send us a photo.

Treat or Remove? How to Make the Call

Here's the honest framework we give Knoxville homeowners:

• Treat when the cause is bagworms caught early, drought stress with mostly-green foliage, or normal needle shed.
• Prune and monitor when seiridium canker is limited to a few branches and the trunk is clean.
• Remove when the tree is more than 50% brown, a canker has girdled the main trunk, or root rot is driving bottom-up decline. A Leyland past these thresholds will not come back — and because conifers can't refill bare branches, even a “survivor” never works as a privacy screen again.

There's a safety clock ticking, too. Dead Leyland cypress turn brittle fast. The wood dries, the shallow root plate decays, and a tree that was a soft green wall in June becomes a 40-foot lever in a January wind storm — typically aimed at the fence, driveway, or neighbor's yard it was planted beside. Dead leylands are one of the most common storm failures we respond to, and removing them on your schedule is always cheaper than removing them off your roof.

What It Costs to Remove Dead Leyland Cypress in Knoxville

Good news first: compared to a mature oak, Leyland cypress removal is on the affordable end. Most run $150 to $400 per tree depending on height, trunk diameter, and how close they stand to fences, sheds, and property lines. Because leylands are almost always planted in rows, crews can set up once and work down the line — which is why row discounts make the per-tree price drop as the count goes up.

A typical job — say, a row of eight 25-foot dead leylands along a back fence — usually lands well under what a single large hardwood removal costs, especially with stump grinding bundled per stump. If you're clearing a long privacy row to re-landscape, that starts to look more like a small lot clearing project, which is often priced as one package instead of per tree. For context on how these numbers fit the broader market, see our full Knoxville tree removal cost breakdown. Every quote we give is a free written estimate — no surprises on invoice day.

What to Plant Instead in East Tennessee

If you're replacing a failed Leyland row, don't replant the same problem. Three screens that handle East Tennessee conditions better:

• ‘Green Giant’ arborvitae — the go-to Leyland replacement. Nearly as fast (around 3 feet a year), similar height and shape, but far more resistant to canker diseases and more tolerant of our humidity. If you want the same green wall with fewer funerals, this is it.
• Eastern red cedar — a tough Tennessee native that shrugs off drought, clay, heat, and cold. Slower growing, but it feeds songbirds, and a native windbreak is about as low-maintenance as screens get.
• ‘Nellie Stevens’ holly — a dense, glossy broadleaf evergreen that reaches 15–25 feet, takes shearing well, and brings red winter berries. Excellent where you want a screen that's also an ornamental.

Whatever you choose, fix the conditions that killed the leylands first: space trees properly (crowded rows stay damp and trade diseases), improve drainage in soggy spots, and water deeply through the first two summers. Your county UT Extension office can test your soil for a few dollars before you replant — cheap insurance against repeating history. And if you're starting from scratch, we can grind the old stumps and handle the removal end to end so the new row goes into clean ground.

Frequently Asked Questions

Sources

• Leyland cypress diseases, insects & related pests — seiridium canker, bagworms, root rot: Clemson University Home & Garden Information Center
• Tennessee-specific plant disease guidance & soil testing: University of Tennessee Extension and its Extension publications library
• Knoxville growing-zone conditions: USDA Plant Hardiness Zone Map
• Removal pricing reflects current Knoxville-market figures from our own free estimate data.

Related Resources

• Signs a Tree Is Dying: A Knoxville Homeowner's Checklist
• Storm Damage & Hazard Tree Removal in Knoxville
• Tree Removal Cost in Knoxville
• Lot & Brush Clearing Services