Browning on a Mr. Bowling Ball arborvitae almost always traces to one of a handful of environmental stresses rather than a fatal disease, with winter desiccation and improper watering being the two most frequent culprits. This compact, globe-shaped cultivar of Thuja occidentalis is popular precisely because it stays small and tidy, but that dense foliage can mask problems until they become dramatic. The good news is that most causes of browning are identifiable by when and where the discoloration appears on the plant, and most are correctable once you know what you’re dealing with.
Winter Burn Is the Most Common Cause
If the browning showed up in late winter or early spring, there’s a strong chance you’re looking at winter desiccation. Arborvitae are evergreen, meaning their foliage continues to lose moisture through transpiration even during cold months. When the ground is frozen, the roots can’t pull water from the soil to replace what the leaves are losing. Add in bright winter sunshine or drying wind, and the foliage essentially dehydrates from the inside out. Research on young conifers wintering in frozen soil confirmed that damage results from this combination of soil freezing and sun exposure, not from cold temperatures alone.1Ecology. Mechanism of Desiccation Damage of Conifers Wintering in Soil‐Frozen Areas
The telltale pattern is browning concentrated on the side of the plant that faces the prevailing wind or the most afternoon sun. On a Mr. Bowling Ball, which is only about two to three feet across, the damage can look like it covers the whole plant because there’s just less surface area for it to spread over compared to a tall arborvitae hedge. The foliage turns tan or bronze, feels dry and papery, and the discoloration often starts at the tips of the sprays rather than at the base.
The frustrating part is that you won’t notice winter burn until conditions warm up and it’s already happened. Prevention is the real strategy here. Water the plant deeply in late fall before the ground freezes, so it enters winter with fully hydrated roots. A two-to-three-inch layer of mulch around the base helps insulate the root zone and delay soil freezing. For plants in particularly exposed spots, a burlap windscreen on the windward side can reduce moisture loss enough to prevent damage. Anti-desiccant sprays exist and are marketed for this purpose, though their effectiveness is debated among horticulturists and they need reapplication after rain or warm spells.
Too Much or Too Little Water
Outside of winter, watering issues are probably the second most common reason a Mr. Bowling Ball turns brown, and the tricky part is that overwatering and underwatering produce symptoms that look similar at first glance.
Underwatering is more straightforward. Arborvitae have shallow, fibrous root systems, and in hot or windy weather they can dry out faster than you’d expect, especially in the first couple of years after planting when roots haven’t fully established. Browning from drought tends to start at the tips of the outer foliage and works inward. The foliage feels crispy and dry. If you pull back the mulch and the soil beneath is bone-dry several inches down, drought is your likely answer.
Overwatering is sneakier. Mr. Bowling Ball arborvitae need well-drained soil. When planted in heavy clay or in low spots where water pools, the roots sit in saturated conditions and start to rot. Root rot reduces the plant’s ability to take up water, so the aboveground symptoms mimic drought even though the soil is soaking wet. The browning tends to be more diffuse across the whole plant rather than concentrated on one side. If you dig down a few inches and the soil smells sour or the roots look dark and mushy instead of white and firm, you’re dealing with too much water rather than too little.
The fix for underwatering is simple: water deeply once or twice a week during dry spells rather than giving the plant a quick sprinkle every day. Deep watering encourages roots to grow down rather than staying at the surface. For overwatering, the solution may require improving drainage, raising the planting bed, or in severe cases moving the plant to a better-drained location. Once root rot has progressed significantly, the plant may not recover regardless of what you do.
Salt Damage from Roads and Sidewalks
If your Mr. Bowling Ball sits near a road, driveway, or sidewalk that gets de-icing salt in winter, salt spray could be the cause of browning. This is an underappreciated problem for arborvitae specifically. A study of white cedar (the same species as your Mr. Bowling Ball, Thuja occidentalis) and pine trees along highways in southern Ontario documented severe foliar injury from road salt. Browning was visible on trees up to 120 meters from the road surface, was concentrated on the downwind side of the highway, and was worst on the windward face of the tree and in exposed positions.2Canadian Journal of Botany. Injury on roadside trees: leaf injury on pine and white cedar in relation to foliar levels of sodium and chloride
The mechanism is straightforward. Vehicles kick up a fine mist of salt water that drifts onto nearby vegetation. Sodium and chloride accumulate in the foliage and cause tissue death. The pattern is distinctive: browning is worst on the side of the plant facing the road, and it shows up in spring once temperatures rise and the damage becomes visible. If only the road-facing side of your Mr. Bowling Ball is brown and the rest looks healthy, salt spray is a strong suspect.
Salt can also reach the plant through the soil. Meltwater carrying dissolved road salt can flow into planting beds, raising sodium and chloride levels in the root zone. This kind of damage tends to be more uniform across the plant since the toxicity comes up through the roots rather than landing on one side.
There’s no way to “undo” salt damage to foliage that has already turned brown. You can minimize future harm by flushing the soil around the plant with deep watering in early spring to dilute salt concentrations, repositioning the plant further from the salt source if possible, or switching to a less salt-sensitive species in that particular spot. Some landscapers install physical barriers like low hedges or fences between the road and sensitive plantings to intercept salt spray.
Pests That Target Arborvitae
Several insects feed on arborvitae and can cause browning. The damage patterns differ depending on the pest, and knowing which one you’re dealing with matters because the treatment approaches are different.
Bagworms
Bagworms (Thyridopteryx ephemeraeformis) are among the most damaging pests of arborvitae and other evergreens. The larvae construct spindle-shaped bags from silk and bits of foliage, which they carry around as they feed. On a Mr. Bowling Ball, the bags blend in remarkably well with the dense foliage, so an infestation can progress significantly before you notice it. Females lay their eggs inside their pupal cases, where the eggs overwinter and hatch the following spring. Larvae go through multiple stages of development over roughly three months as they feed and enlarge their bags.3Oxford Academic. Observations on the Biology and Behavior of the Evergreen Bagworm Moth, Thyridopteryx ephemeraeformis
The browning from bagworms tends to be patchy and scattered rather than following the clean one-sided pattern of winter burn or salt damage. You may see individual branches or sections of the plant turning brown while adjacent areas stay green. Look closely for the bags themselves, which range from half an inch to about two inches long depending on the larval stage. On a small plant like Mr. Bowling Ball, even a modest number of bagworms can strip enough foliage to cause serious harm.
If you catch an infestation early, handpicking the bags off the plant and destroying them is surprisingly effective, especially on a compact cultivar where you can reach the entire plant. For larger infestations, Bt (Bacillus thuringiensis) sprays work well when applied while the larvae are still small and actively feeding, typically in late spring to early summer. The key is timing: once the larvae seal themselves inside their bags to pupate in late summer, sprays won’t reach them.
Leaf Miners
Arborvitae leaf miners are small moth larvae that tunnel inside the flattened leaf scales, feeding on the tissue from within. Research in New Brunswick documented conspicuous browning on arborvitae caused by leaf miners, which became increasingly noticeable over successive years as populations built up.4Cambridge University Press. Studies on the Arborvitae Leaf Miners in New Brunswick The browning from leaf miners looks different from bagworm damage. Instead of whole branches dying, you’ll see individual leaf tips turning brown while the base of the same leaf spray stays green. If you hold a browned leaf tip up to the light, you can sometimes see the hollowed-out interior where the larva has been feeding, or find the tiny larva itself inside.
Leaf miner damage is usually more cosmetic than fatal, especially on an established plant. But on a Mr. Bowling Ball, where the entire plant might be only a couple of feet across, even cosmetic damage is highly visible. Systemic insecticides applied as a soil drench in spring can control leaf miners before damage becomes apparent, since the active ingredient is taken up by the roots and distributed through the foliage. Pruning out heavily mined tips in fall or winter can reduce the overwintering population.
Spider Mites
Spider mites are another pest worth checking for, particularly during hot, dry summers. These are tiny arachnids that feed by piercing individual leaf cells and sucking out the contents. Heavy infestations give the foliage a stippled, bronzed appearance that progresses to full browning. You can confirm their presence by holding a piece of white paper under a branch and tapping sharply. Mites will fall onto the paper and appear as tiny moving specks. Fine webbing between leaf sprays is another giveaway. A strong blast of water from a hose knocks mites off the plant and can keep populations in check if done regularly. Horticultural oil or insecticidal soap sprays are effective for heavier infestations.
Fungal Diseases
Several fungal pathogens can cause browning on arborvitae, though they are less common culprits than the environmental stresses described above. Kabatina tip blight and Pestalotiopsis tip blight both kill the tips of branches, turning them brown, and tend to show up in spring on growth from the previous year. These fungi typically gain entry through wounds or stressed tissue, so a plant that has been weakened by drought, salt, or winter burn is more susceptible than a healthy one.
Phytophthora root rot is more serious. This water mold thrives in poorly drained, consistently wet soil and attacks the roots, cutting off water and nutrient uptake. The aboveground symptoms look like drought stress, with browning that progresses from the lower parts of the plant upward. If the lower interior of your Mr. Bowling Ball is browning while the top still looks green, and the soil stays wet for long periods after rain, Phytophthora could be at play. Unlike tip blight fungi, Phytophthora can kill the entire plant if soil conditions aren’t corrected.
Fungal tip blights are usually managed by pruning out affected branches during dry weather and improving air circulation around the plant. Fungicide sprays are available but are more of a preventive measure than a cure for already-browned foliage. For Phytophthora, improving drainage is the essential step; fungicide drenches with phosphonate-based products can help but won’t compensate for chronically waterlogged soil.
Natural Interior Browning
Not all browning is a problem. Arborvitae naturally shed their oldest interior foliage every fall. The innermost needles, which are shaded by the newer outer growth and no longer contribute much to photosynthesis, turn brown and drop. On a Mr. Bowling Ball, this can be alarming because the dense, rounded form means you might not notice the interior until you part the outer foliage and find brown underneath.
Natural shedding has a few distinguishing features. It happens in autumn, it’s confined to the interior of the plant rather than the tips or outer surfaces, and the outer growth stays green and healthy. If you gently shake the plant or run your hand through the interior, the dead foliage will fall out readily. This is normal and does not indicate disease or stress. Every arborvitae does it. The only action needed is to brush out the dead foliage occasionally so it doesn’t accumulate and trap moisture against the stems, which could encourage fungal problems.
How to Diagnose Your Specific Problem
Since so many different issues produce browning, the most useful diagnostic approach is to note the pattern and timing of the discoloration:
- One-sided browning, spring: Winter desiccation or salt spray, depending on whether the brown side faces the wind/sun or the road.
- Browning at tips, summer: Drought stress, spider mites, or leaf miners. Check soil moisture, look for mites with the paper test, and examine leaf tips for hollowed-out interiors.
- Patchy browning with visible bags: Bagworms. Look for the characteristic spindle-shaped cases attached to branches.
- Browning from the bottom up: Root rot from overwatering or Phytophthora, especially if the soil is consistently wet.
- Interior browning in fall: Normal seasonal shedding. No treatment needed.
- Uniform browning across the whole plant: Could be soil-level salt contamination, severe drought, or root damage from transplant shock if the plant was recently moved.
When the cause isn’t obvious from the pattern alone, take a sample of affected foliage to your local cooperative extension office. Most state extensions offer free or low-cost plant diagnostics and can identify fungal pathogens, insect damage, or nutrient deficiencies from a physical sample far more reliably than any visual guide online.
Helping a Browned Mr. Bowling Ball Recover
Once foliage on an arborvitae turns brown, those specific leaves will not turn green again. Arborvitae don’t regenerate from old wood the way some broadleaf shrubs do, so recovery depends on whether the branches beneath the brown foliage are still alive. You can check this by scraping a small section of bark on a browned branch with your thumbnail. If the tissue underneath is green, the branch is alive and capable of pushing new growth. If it’s brown and dry all the way through, that branch is dead and should be pruned out.
For plants with significant dieback, resist the urge to prune aggressively all at once. Remove clearly dead material and give the plant a full growing season to respond. Ensure it has consistent moisture through the growing season, and apply a balanced slow-release fertilizer in early spring to support new growth. Mr. Bowling Ball grows slowly, so recovery from extensive browning takes patience. A plant that lost a third of its foliage to winter burn may need two full growing seasons to fill back in.
If more than half the plant is dead, replacement may be more practical than rehabilitation. When replanting, consider whether the original spot contributed to the problem. A location with better wind protection, improved drainage, or more distance from a salted road could prevent a repeat. Planting in spring rather than fall gives the root system a full growing season to establish before facing its first winter, which reduces the risk of winter desiccation considerably.
Choosing the Right Spot in the First Place
Mr. Bowling Ball arborvitae are marketed as low-maintenance, and they genuinely are once established in a suitable location. But “suitable” is doing real work in that sentence. They want full sun to partial shade, with at least four to six hours of direct sunlight. They need soil that drains well but stays moderately moist. They’re rated for USDA hardiness zones 3 through 8, which covers a huge swath of North America, but cold-zone plantings in exposed locations are much more prone to winter damage than the same cultivar tucked against a south-facing wall.
Spacing matters even though the plant is small. Placing a Mr. Bowling Ball too close to a wall, fence, or other plant restricts air movement through the foliage and creates humid microclimates that favor fungal problems. A foot or two of clearance on all sides goes a long way. Similarly, avoid planting directly beneath roof eaves where ice and snow can slide off and crush the plant, or where drip from the roofline creates an artificially wet root zone.
One underappreciated siting consideration is reflected heat. A Mr. Bowling Ball planted next to a south-facing concrete or brick wall can experience temperatures significantly higher than the ambient air on summer afternoons. That heat stress, combined with the drying effect of reflected light, can cause foliage scorch that looks like drought damage even when soil moisture is adequate. If you have a spot that gets baked by reflected heat in summer and blasted by cold wind in winter, it’s a tough spot for any arborvitae regardless of cultivar, and a different plant might serve you better there.