Boxwood Blight : Understanding, Prevention, and Treatment

What is Boxwood Blight?

Boxwood, known for its evergreen foliage and versatility in landscaping, is a cherished plant in gardens around the world. However, a concerning issue that has emerged in recent years is the prevalence of boxwood blight, a fungal disease that poses a significant threat to these beloved shrubs. In this comprehensive article, we will delve deep into the intricacies of boxwood blight, exploring its nature, preventive measures, treatment options, and its impact on the horticultural world.

Boxwood blight, caused by the fungi Calonectria pseudonaviculata and Cylindrocladium pseudonaviculatum, is a devastating disease affecting boxwood plants (Buxus spp.). First identified in the mid-1990s, this pathogen has since spread across regions, becoming a major concern for gardeners, landscapers, and horticulturists alike. The disease thrives in warm and humid conditions, making it particularly problematic during periods of damp weather.

Recognizing the Symptoms

The symptoms of boxwood blight are a complex blend of subtlety and severity, making early detection a critical aspect of management. The disease exhibits a burstiness of symptoms, ranging from minor to severe, which underscores the challenge of diagnosis. Initially, small dark spots appear on leaves, accompanied by elongated lesions. Over time, these spots expand, developing into larger, irregular lesions that turn brown or straw-colored. The infection progresses, leading to leaf drop, branch dieback, and cankers on stems. The contrast between the healthy and infected foliage, coupled with the burstiness of symptom presentation, is a hallmark of boxwood blight.

Boxwood Blight Prevention Strategies

Preventing boxwood blight demands a multifaceted approach that encompasses cultural practices, careful plant selection, and vigilant maintenance. By employing a diversity of strategies, you create a burstiness that prevents the fungus from adapting and thriving:

1. Proper Plant Spacing

Maintaining adequate space between boxwood plants is essential to reduce humidity buildup, creating an environment less conducive to fungal growth. Proper spacing promotes air circulation, which is key to preventing conditions favorable to the development of boxwood blight. In densely planted areas, moisture tends to accumulate, providing an ideal setting for the disease to flourish. By creating space between plants, you minimize the chances of the fungus taking hold.

2. Sanitation Practices

A burst of proactive garden hygiene is crucial. Swiftly remove fallen leaves, prune infected branches, and sanitize tools to prevent the spread of the disease. Infected plant material left on the ground can serve as a source of spores, allowing the disease to persist and spread. Regularly cleaning up fallen leaves and other debris reduces the available inoculum, limiting the disease’s ability to infect healthy plants. Additionally, pruning infected branches helps contain the spread of the disease within the affected plant.

3. Selection of Resistant Varieties

Opt for boxwood varieties known for their resistance to the disease. This not only perplexes the fungus but also ensures your garden remains visually appealing. Some boxwood cultivars exhibit a degree of resistance to boxwood blight, offering an effective burst of defense against the disease. When selecting plants for your garden, research and choose varieties that have demonstrated a level of tolerance to the pathogen. While no variety is entirely immune, planting resistant cultivars can reduce the risk of severe infection. A great option is the Green Velvet Boxwood variety. This variety has been proven to be “less” susceptible to Boxwood Blight!

4. Improved Air Circulation

Strategic pruning enhances air circulation, reducing humidity levels around the plants and hindering the colonization of the fungus. By selectively pruning dense areas of the plant, you promote better airflow, which helps prevent the prolonged leaf wetness that encourages fungal growth. When planning your pruning regiment, focus on creating a balanced and open structure for the boxwood shrubs. Thinning out crowded sections of the plant allows sunlight to reach more of the foliage and reduces the chances of humid microclimates forming within the shrub.

Treating Boxwood Blight

When boxwoods fall prey to blight, timely action can minimize the damage. Here’s a burst of approaches to consider for treating the disease:

1. Fungicides

Fungicides, when used under the guidance of a professional, offer a targeted solution. Their intricate formulations specifically target the fungus, curbing the perplexing spread of the disease. Fungicide application is most effective as a preventive measure or in the early stages of infection. Consult with a knowledgeable horticulturist or arborist to determine the appropriate fungicide and application schedule for your specific situation. Remember that while fungicides can help manage the disease, they are just one component of an integrated management strategy.

2. Pruning and Disposal

Surgical removal of infected branches and leaves impedes the disease’s progress, preventing further spread. Regularly inspect your boxwood shrubs for signs of infection, and promptly prune out any affected plant parts. Be sure to disinfect pruning tools between cuts to avoid inadvertently spreading the disease. Once the pruned material is removed, it’s crucial to properly dispose of it. Burn,  or bag and seal the infected plant material for disposal, as these methods prevent the release of disease-causing spores back into the environment.

3. Cultural Modifications

Adjusting irrigation practices to keep foliage dry and minimizing overhead watering creates an environment less favorable to fungal growth. Overhead irrigation can contribute to prolonged leaf wetness, which is conducive to the development of boxwood blight. Consider switching to drip irrigation or soaker hoses to water the plants at the soil level, rather than wetting the foliage. If overhead watering is necessary, aim to do so in the morning, allowing ample time for the foliage to dry during the day. Additionally, spacing plants appropriately and pruning for improved air circulation help reduce humidity levels around the shrubs.


In navigating the intricate world of boxwood blight, it becomes clear that a varied and diverse approach is crucial to maintaining healthy shrubs. At Greenhouse to Garden, we understand the significance of safeguarding your outdoor spaces. Our business, rooted in the Greater Toronto Area, offers an extensive array of annuals, perennials, trees, and shrubs for sale. Moreover, our landscape design and plant care services provide a burst of solutions to ensure your green spaces flourish. Armed with the knowledge shared in this article, you’re equipped to protect your boxwoods and nurture a garden bursting with vitality.

In the face of the complex challenges posed by boxwood blight, remember that proactive and diverse strategies can effectively prevent and manage the disease.

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