Why Are My Boxwoods Dying and How to Revive Them

Boxwoods are a popular choice for hedges and topiaries, but they can be finicky.

Drought stress is a common cause of boxwood decline, as these plants prefer consistently moist soil.

Overwatering can also be a problem, as boxwoods are susceptible to root rot in waterlogged soil.

A lack of nutrients can cause boxwood leaves to turn yellow and drop, a sign of nitrogen deficiency.

Boxwoods are also vulnerable to pests like spider mites and scale, which can weaken the plant and make it more susceptible to disease.

Boxwoods turning brown and dying can be attributed to two primary soil-borne diseases: Phytophthora root rot and English boxwood decline. Both diseases pose significant threats to various boxwood species.

Phytophthora root rot is caused by a fungus-like organism that thrives in wet, poorly-drained soils. This can lead to a decline in health as the plant's ability to absorb water and nutrients is compromised. Yellowing leaves, reduced growth, and eventual browning are symptoms of this disease.

English boxwood decline is a less understood condition that primarily affects the English boxwood. Symptoms start with the lightening of leaf color, progressing to leaf drop and significant thinning of the foliage. This decline is gradual and can be exacerbated by stress factors such as extreme temperatures, drought, or improper planting.

Related reading: Dwarf English Boxwoods

Winter injury is the most common problem that affects boxwood, and it's often apparent as the snow recedes, revealing brown leaves and stems on the boxwoods.

Buxus sempervirens is typically hardy down to USDA Zone 5, but plants are especially susceptible to winter damage in temperatures below -10 degrees Fahrenheit.

Winter damage is especially distinctive in that the growth below the former snowline is still green, making it a clear sign of injury.

Growers can just prune out or prune off the damaged foliage if the damage is not overly severe, allowing the healthy growth to thrive.

Curious to learn more? Check out: How to Prune Boxwoods with Winter Damage

Boxwoods turning brown and dying can be attributed to two primary soil-borne diseases: Phytophthora root rot and English boxwood decline.

Phytophthora root rot is a serious threat to boxwood species, including the American boxwood (Buxus sempervirens), English boxwood (B. sempervirens 'Suffruticosa'), and littleleaf boxwood (B. microphylla). This disease is caused by a fungus-like organism that thrives in wet, poorly-drained soils.

Symptoms of Phytophthora root rot include yellowing leaves, reduced growth, and eventual browning as the plant dies back. This decline in health is due to the plant's inability to absorb water and nutrients.

English boxwood decline, on the other hand, primarily affects the English boxwood. Symptoms start with the lightening of leaf color, progressing to leaf drop and significant thinning of the foliage.

The decline is gradual and can be exacerbated by stress factors such as extreme temperatures, drought, or improper planting.

Here are the two primary diseases that can cause boxwood death, along with their symptoms:

Boxwood plants can be affected by several specific diseases that can cause them to die. Volutella stem canker is one such disease, caused by the fungal pathogen Pseudonectria buxi.

Moist weather is conducive to the development of Volutella infection, which can lead to the bronzing and yellowing of leaves before new growth in spring. The fungus produces salmon/pink fruiting bodies on the undersides of the leaves.

One distinguishing difference between Volutella and boxwood blight is the color of the fruiting bodies, which are pink-salmon for Volutella and gray-white for boxwood blight.

Volutella stem canker is a fungal disease that affects boxwood plants, caused by the pathogen Pseudonectria buxi. It's a common problem that can cause significant damage to your boxwood plants.

In the spring, before new growth appears, the leaves will bronze and yellow, which is a clear indication of the disease. This discoloration is a result of the fungus's presence.

A unique perspective: Succulent Plants Dying

Moist weather conditions are ideal for the development of Volutella infection. It's essential to keep an eye on your plants during periods of high humidity.

The fungus produces salmon/pink fruiting bodies on the undersides of the leaves, which is a distinctive characteristic of the disease. These fruiting bodies are a key identifier of Volutella stem canker.

As the disease progresses, the bark on infected branches can become loose and dieback, often resulting in the complete death of part of the plant. This can be a devastating outcome for your boxwood plants.

One way to distinguish Volutella stem canker from boxwood blight is to examine the color of the fruiting bodies. Volutella produces pink-salmon fruiting bodies, while boxwood blight produces gray-white fruiting bodies.

Boxwood Leafminer is a common issue that can cause significant damage to your boxwood plants. The adult leafminer, a mosquito-like fly, lays its eggs between the layers of the leaf.

Infested leaves will develop brown patches as the larvae grow, and heavily infested leaves will defoliate in the late fall and early spring. This can be a major problem for gardeners who rely on their boxwood for hedges or topiaries.

The emerging adults leave an emergence hole in the leaf where they exited, which can be a giveaway that you have a leafminer problem.

Winter burn is a common problem that can cause your boxwoods to turn yellow or die. This happens when cold winter winds and weather damage the plant, causing the leaves to turn pale yellow.

Erecting some sort of cold wind protection, like burlap wraps, can help minimize winter damage. A thick layer of mulch around your boxwoods can also keep the roots warmer.

Desiccation is another issue that can affect boxwoods, especially in areas like Denver, where the sun is intense and the ground is frozen. This can cause the plant to lose too much water through transpiration.

Winter watering can help alleviate desiccation, but only when the ground isn't frozen. It's also essential to site your boxwoods out of south and western exposures to reduce the risk of desiccation.

Boxwood blight is a serious fungal disease that can cause boxwood leaves to turn brown or yellow and drop. However, it's unlikely if your boxwoods are only showing yellow leaves, as this disease often causes more severe symptoms.

Pruning your boxwoods can help them survive hard times, and they may even fill back in over time.

For another approach, see: Why Are My Boxwoods Turning Yellow

Reviving a dying boxwood requires prompt action to address the root cause of the decline. One of the most critical steps is to improve soil drainage, as root rot is often caused by poor drainage. If your boxwoods are planted in an area with poor drainage, consider replanting them in a raised bed or incorporating organic matter to improve soil structure.

Overwatering is another common mistake that can lead to root rot. Water your boxwoods only when necessary, allowing the soil to dry out between waterings. This will help prevent the buildup of excess moisture that can cause root rot.

Pruning dead or diseased branches is also essential to prevent the spread of disease. Sterilize your pruning tools between cuts to avoid contaminating healthy parts of the plant. By pruning affected areas, you can help your boxwoods recover and prevent further decline.

In cases of Phytophthora root rot, a fungicide may be necessary to control the disease. Follow the product's instructions carefully and consider consulting a professional for application. This will help ensure the fungicide is used effectively and safely.

To help your boxwoods recover, make sure to maintain their overall health through proper care. This includes fertilization, mulching, and pest control measures. By providing your boxwoods with the right conditions, you can help them become more resilient to disease and stress.

Here are some key steps to revive your boxwood: