Boxwood shrubs are a popular choice for many home gardens. Their simple and pale green leaves add a touch of elegance to any landscape. However, as an amateur gardener, you may find yourself puzzled when your once healthy boxwood starts turning yellow.
There can be many causes for this yellowing phenomenon, and understanding them is crucial for maintaining the beauty of your garden. In this article, we will explore four common reasons why boxwood shrubs turn yellow and what you can do to address them.
One possible cause of yellowing boxwood leaves is environmental conditions. Boxwoods are known to be sensitive to extreme temperatures, both hot and cold. Overly hot summers or cold winters can stress the shrubs, causing their leaves to turn yellow. Additionally, boxwoods may suffer from winter damage, especially if they are not protected adequately. Therefore, it is essential to provide proper care and protection to your boxwoods during extreme weather conditions.
Another common culprit for yellowing boxwood shrubs is disease. Boxwood blight, a fungal disease, can cause leaves to turn yellow and eventually brown. This disease is highly contagious and can spread rapidly throughout your garden. To prevent the spread of boxwood blight, it is crucial to practice good sanitation, using clean tools and disposing of infected material properly.
Furthermore, insufficient watering can also lead to yellowing boxwood shrubs. Boxwoods require moist but well-drained soil to thrive. If the soil in which they are planted is too dry or consistently wet, the shrubs may suffer from stress, resulting in yellow leaves. It is important to water your boxwoods regularly, ensuring that the soil is evenly moist but not waterlogged.
Last but not least, nutrient deficiencies can cause boxwood leaves to turn yellow. Boxwoods require essential nutrients, such as nitrogen, phosphorus, and potassium, to maintain their green color. If these nutrients are lacking in the soil, the shrubs may show signs of yellowing. Applying a balanced fertilizer designed for boxwoods can help rectify this deficiency and promote healthy growth.
In conclusion, yellowing boxwood shrubs can be caused by a variety of factors, including environmental conditions, disease, insufficient watering, and nutrient deficiencies. By understanding the cause of the yellowing and taking appropriate actions, you can maintain the beauty and health of your boxwood shrubs for years to come.
1 Winter weather
One of the main reasons why boxwood shrubs may turn yellow is due to the effects of winter weather. The cold temperatures and harsh conditions that come with the winter season can cause stress to boxwoods, resulting in discoloration and yellowing of the leaves.
According to experts, boxwoods are generally hardy and can tolerate winter conditions. However, if the temperatures drop too low or if there are extreme weather conditions, they can be negatively affected.
During winter, boxwood shrubs enter a period of dormancy where their growth slows down significantly. This makes them more vulnerable to the effects of cold temperatures and can cause their leaves to turn yellow.
John Negus, a gardening expert, explains that boxwoods are evergreen shrubs, meaning they should remain green throughout the year. However, the cold winter temperatures can cause the leaves to lose their green color and turn yellow.
In addition to the cold temperatures, winter weather can also lead to other issues that can cause yellowing of boxwood leaves. For example, dry winter winds can cause the shrubs to lose moisture, resulting in dehydration and leaf discoloration. Similarly, freezing and thawing cycles can cause the soil to dry out, making it harder for the boxwood shrubs to absorb water and nutrients.
To protect your boxwood shrubs from winter weather damage, there are a few steps you can take. Consider covering your shrubs with burlap or a protective barrier to shield them from cold winds. Additionally, watering the shrubs deeply in late fall before the ground freezes can help ensure they have enough moisture to withstand the winter.
It’s important to note that while winter weather can be a significant cause of yellowing, it’s not the only factor. There are other potential causes of discoloration in boxwood shrubs, such as disease, nutrient deficiencies, and improper pruning. Therefore, it’s essential to consult with a professional or do further research to determine the exact cause of yellow leaves on your boxwood shrubs.
2 High temperatures
One common reason for boxwood shrubs turning yellow is high temperatures. Boxwood shrubs are known for their ability to tolerate a wide range of temperatures, but extreme heat can cause stress and lead to yellowing of the leaves.
During the summer months, especially in July, when temperatures are at their highest, boxwood shrubs may start to turn yellow. This is because the high temperatures can cause the plants to lose moisture faster than they can absorb it from the soil. The lack of moisture can lead to drought stress and result in yellowing leaves.
In winter, on the other hand, boxwood shrubs can also turn yellow due to cold temperatures. Freezing temperatures can damage the roots and prevent the shrubs from absorbing water properly. As a result, the leaves may turn brown or yellow.
It is important to note that boxwood shrubs can be affected by high temperatures even if they are grown in shaded areas or well-maintained gardens. Therefore, it is crucial to provide the necessary care and protection to prevent yellowing of the leaves.
To mitigate the effects of high temperatures on boxwood shrubs, there are some simple gardening ideas you can follow:
- Water the shrubs deeply and regularly during dry and hot periods. This will help replenish the moisture lost due to evaporation and maintain the health of the shrubs.
- Apply a layer of organic mulch around the base of the shrubs. Mulch helps retain moisture in the soil and prevents weed growth, which can compete with boxwood shrubs for water.
- Provide some shade to the shrubs during the hottest parts of the day. This can be done by strategically placing a shade cloth or using nearby trees or structures to cast shadows over the plants.
- Consider using anti-transpirant sprays or applying sunscreen to the leaves. These products can help reduce water loss through transpiration and protect the leaves from sunburn.
If your boxwood shrubs have been turning yellow for many years, despite following these care tips, it may be necessary to consult an expert for further assistance. They can assess the specific conditions in your garden and provide tailored advice to help restore the health of your shrubs.
3 Box blight
If your boxwood shrubs are turning yellow and their leaves are becoming pale or brown, you may be dealing with box blight. This fungal disease affects many boxwood gardens and can cause significant damage if not addressed promptly.
Box blight is caused by the pathogen Cylindrocladium buxicola, which thrives in cool and humid conditions. It is most common in the spring and fall when temperatures are mild and the air is often damp. This disease can also be triggered by extended periods of wet weather or poor air circulation.
One of the symptoms of box blight is the yellowing of the leaves. As the disease progresses, the leaves may turn brown and fall off, leaving the shrub looking bare and unhealthy. In severe cases, the entire bush may die.
There are several simple steps you can take to prevent and manage box blight in your garden:
- Prune affected shrubs: If you notice yellow or brown leaves on your boxwood shrubs, prune the affected branches immediately. Be sure to disinfect your pruning tools between cuts to prevent the spread of the disease.
- Improve air circulation: Trim nearby plants and remove any debris that may be blocking air flow around your boxwood shrubs. This will help reduce humidity and create a less favorable environment for the fungus to thrive.
- Monitor watering: Overwatering can promote the growth of fungal diseases like box blight. Make sure your boxwoods are only receiving the necessary amount of water and that the soil is well-drained.
- Treat with fungicides: If your boxwoods are already affected by box blight, you can use fungicides to help manage the disease. Consult with a gardening expert or check product labels for the appropriate fungicide to use on boxwoods.
Remember that prevention is key when it comes to box blight. By keeping your boxwood shrubs healthy and providing them with optimal growing conditions, you can reduce the risk of this fungal disease affecting your garden.
John Negus, an amateur gardener with years of experience, explains that box blight has become more common in recent years due to changes in weather patterns and gardening trends. He suggests choosing boxwood varieties that are more resistant to fungal diseases and regularly monitoring the health of your shrubs to catch any issues early on.
4 Caterpillars and other pests
One possible cause for the yellowing of boxwood shrubs is the presence of caterpillars and other pests. These insects can cause significant damage to the leaves and overall health of the plant.
Caterpillars are the larval stage of certain moths and butterflies, and they can be a common problem for boxwood shrubs. The larvae feed on the leaves of the shrub, causing yellowing and browning. There are several types of caterpillars that can affect boxwood, including the boxwood leafminer, the boxwood webworm, and the boxwood psyllid.
The boxwood leafminer is a small fly that lays its eggs on the underside of boxwood leaves. When the eggs hatch, the larvae burrow into the leaves and feed on the tissue, causing yellowing and eventually brown discoloration. The boxwood webworm is a small moth whose larvae create webby nests in the shrub’s foliage. These nests trap their prey, and the larvae feed on the trapped insects as well as the leaves of the shrub. The boxwood psyllid is a small insect that feeds on the sap of the boxwood leaves, causing stippling and yellowing.
In addition to caterpillars, other pests such as mites, aphids, and scale insects can also attack boxwood shrubs. These pests feed on the sap of the leaves, causing yellowing and discoloration. Mites are tiny arachnids that can be difficult to see with the naked eye, but their damage is noticeable as yellowing and bronzing of the foliage. Aphids are small insects that suck sap from the leaves, causing them to become distorted and yellow. Scale insects are small, oval-shaped insects that attach themselves to the leaves and suck sap, causing yellowing and stunted growth.
To prevent and control these pests, regular monitoring of the shrubs is necessary. If you notice any signs of infestation, such as yellowing leaves or the presence of insects, you can take appropriate action. This may include manual removal of the pests, the use of insecticidal soaps or oils, or the application of biological controls.
It is important to remember that the use of pesticides should be done with caution, following the instructions on the product label and considering the potential impact on beneficial insects and the environment. Seeking advice from a gardening expert or professional is recommended to ensure proper pest control measures are implemented.