Boxwood Winter Burn vs Blight – How to Tell the Difference and Prevent Damage

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Robby

Above photo by Peter Aaron, design by Robert Orr + Associates; story and plant photos by Doreen Wynja

Boxwood shrubs have a subdued elegance that shines in every season. Their evergreen presence offers structure and a unifying element in the garden. No matter your garden style — formal, cottage, or contemporary — the ever-adaptable boxwood looks beautiful when planted as a specimen, mass planting, or hedge. If you express your garden style in containers, boxwoods can thrive potted up as a distinct feature or provide a backdrop for annuals, perennials, and seasonal decorations.

Low-maintenance, as well as deer and rabbit resistant, many boxwoods will thrive for you in growing zones 4-9. (Determine your growing zone hereand see our favorite boxwoods at the bottom of the page). If you live in an area that experiences cold temperatures during winter, protecting your boxwoods against winter damage starts with growing healthy and vigorous plants throughout the season. Heres how to grow healthy boxwoods and protect them from winter burn or damage.

Boxwood shrubs are a classic landscaping plant, valued for their versatility, deer resistance, and year-round interest. However, boxwood is prone to two common problems that can quickly damage or even kill plants – winter burn and blight. Learning how to distinguish between and prevent these issues is key to keeping your boxwood healthy.

What Causes Boxwood Winter Burn?

Boxwood winter burn occurs when foliage is damaged by harsh winter winds, extreme cold, winter sunscald, or a combination of factors. Evergreen leaves continue to lose moisture during the winter months through transpiration. Under normal conditions, the roots replace this lost moisture. But if the ground is frozen or plants are exposed to drying winds, the foliage cannot take up enough water to replace what is lost and literally dries out or burns.

Symptoms of winter burn in boxwood include:

  • Tan, brown, or black foliage, typically only on exposed portions of the plant. This often appears as a distinct line or “snowline” where protected foliage remains green.

  • Damage only appears on outer portions of plants or on side facing prevailing winds Inner branches are often protected

  • Burned foliage drops off leaving bare stems.

  • Damage is usually most severe following a winter with little protective snow cover, extreme cold, warm periods with sunny days and freezing nights, or Exposure to winter winds.

What Causes Boxwood Blight?

Boxwood blight is a fungal disease that can quickly defoliate and kill boxwoods. This very contagious disease spreads rapidly during cool, moist conditions. Boxwood blight can happen any time the weather is cool and humid, but is most prevalent in spring and fall.

Symptoms of boxwood blight include:

  • Dark or light brown circular leaf spots with dark borders.

  • Black streaks on stems.

  • Rapid defoliation, leaving bare stems.

  • Entire plants turning brown or straw-colored.

  • Rapid plant decline and death, especially on young plants.

  • Defoliation and dieback continues to progress on plants until the entire shrub is affected.

  • Infected leaves and stems have a distinct musty odor.

How to Tell the Difference

While both boxwood blight and winter burn can cause similar leaf browning and defoliation, there are some key differences to look for:

Winter Burn:

  • Damage only on exposed outer portions or one side of plant
  • Distinct snowline between damaged and healthy foliage
  • Worst on outer branches, inner protected branches remain green
  • Tan, burnt appearance to damaged leaves
  • Total extent of damage apparent once weather warms in spring
  • No musty odor

Boxwood Blight:

  • Entire plant becomes infected, not just outer portions
  • Leaves brown from the bottom up or randomly over plant
  • Defoliation and dieback spreads continuously
  • Dark brown leaf spots with black borders
  • Black stems
  • Rapid defoliation in cool, moist weather
  • Musty odor to infected plant parts

How to Prevent Boxwood Winter Burn

While we can’t control the weather, there are a few things you can do to help prevent winter damage on boxwoods:

  • Provide wind protection. Site boxwoods in a location shielded from harsh winter winds, such as against a wall or building on the north or west side of your home. Planting on the south side of the home can actually increase damage by allowing the winter sun to warm plants, leading to moisture loss.

  • Avoid full winter sun. Boxwoods prefer partial shade, especially in winter. Plants in full sun with frozen soil struggle to take up enough moisture to replace transpiration losses.

  • Insulate roots. Apply 2-3 inches of shredded bark mulch around plants to keep roots warmer and prevent soil from freezing.

  • Water in fall. Deep watering before the ground freezes helps boxwoods go into winter well-hydrated.

  • Cover plants. Burlap screens or fabric wraps protect foliage from drying winds and sun. Avoid plastic wraps that can actually cause more damage.

  • Prune for shape and air flow. Maintain a shapely form by removing interior branches and any damaged wood. Allow good air circulation through plants.

  • Choose wind-tolerant varieties. Pick more hardy cultivars like Wintergreen, Winter Gem, or Glencoe.

How to Prevent Boxwood Blight

Preventing boxwood blight involves utilizing cultural practices to keep plants healthy and avoiding introducing the disease:

  • Inspect plants. Examine boxwoods for signs of infection like leaf spots and rapid defoliation. At first signs, begin treatment.

  • Isolate infected plants. Remove and destroy plants with boxwood blight to avoid it spreading.

  • Practice sanitation. Sterilize pruners between plants to avoid transmitting disease. Rake and remove all fallen leaves.

  • Improve air circulation. Allow good spacing between plants and prune to open up interior branches.

  • Water in early morning. Avoid overhead irrigation and water at the soil line to keep foliage dry.

  • Apply fungicides. Protective fungicides may help prevent infection in areas where blight is active.

  • Purchase from reputable nurseries. Ask if their stock is certified disease-free. Avoid boxwoods from unknown sources.

Protect Your Boxwood Investment

Boxwood shrubs have been prized landscape plants for centuries, but they do require proper siting and care. By recognizing the difference between boxwood winter burn and blight, and utilizing preventative practices, you can help keep your boxwood looking healthy for years to come. With a little TLC, the classic boxwood will continue gracing gardens for generations more.

boxwood winter burn vs blight

Boxwood Care in Early Spring

No matter how well you’ve sited or cared for your boxwood, some winters are hard on plants and damage can occur. Late winter or early spring is a good time to evaluate your boxwood for signs of winter damage or disease. The two most common post-winter problems are yellowing foliage and dead and reddish-brown stems. If you live in an area with extreme temperatures during winter, boxwood foliage can sometimes turn yellow. This is most often due to winter burn.

How to Avoid Boxwood Winter Burn or Other Winter Damage

  • Plant your boxwoods in protected sites. The north or east side of your garden is preferable. While not optimal, southern or western exposure can work if there is a nearby windbreak or tree canopy providing shade. A structural barrier such as a solid fence or wall can also serve as a windbreak.
  • If not already ideally located protect existing plants from winter burn and sun exposure in winter with burlap. Set up after the first hard frost.
  • While snow can be a wonderful insulator for plants, heavy loads should be gently brushed off from the tops to prevent breakage. Protect boxwoods from snow and ice damage by wrapping them in burlap (loosely, to allow for airflow) or plastic wildlife netting. Tying up mature boxwoods with twine will ensure that heavy snow loads will slide off and not break branches.
  • Before winter, remove any tender late-season new growth and weak stems to reduce stem injury. (Use the clippings to create a boxwood wreath or a winter-themed window box.)
  • Sanitize gardening tools used in caring for boxwoods with 70% isopropyl alcohol (rubbing alcohol) to limit the spread of any pests or diseases.
  • Once the ground is frozen add a winter layer of mulch (up to 2-3”) to help keep moisture at the roots. Again, be careful not to cover the base stem of the shrub.
  • Consider using an anti-desiccant to protect boxwoods from drying out in the winter wind. Apply before temperatures are reliably below 40 degrees.

Boxwood Winter Burn or Boxwood Blight

FAQ

How do I know if my boxwood is blight?

Symptoms and Signs. Symptoms of boxwood blight on boxwood (Buxus spp.) include leaf spots or blotches, rapid defoliation, and stem lesions (Figs.Sep 22, 2020

Can boxwoods recover from winter burn?

Winter burn is often quite minor, affecting only the branch tips. Simply cut the dead shoot tips back to living tissue by making proper pruning cuts. These plants will recover quickly with new growth in spring.

Can boxwood recover from blight?

There are no treatments to cure boxwood blight. Destruction of affected plants is necessary to control the disease. Preventive treatments may be available.

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