When healthy, boxwood, also known as buxus, showcases a rich, glossy green that enhances your garden's beauty. Unfortunately, the leaves can sometimes turn yellow or brown, detracting from their appeal.
Several factors can lead to this discoloration, ranging from environmental stress to pest infestations. The good news is that most issues can be resolved with some tender loving care, allowing you to potentially revive your evergreen shrubs.
If you've spotted yellowing leaves, don't lose hope — our straightforward guide outlines the possible causes and offers solutions to restore your boxwood to its former glory.
Boxwood makes an excellent choice for formal hedging around flower beds.
1. Impact of Winter Weather
Inclement winter conditions can significantly affect boxwood, as noted by the Royal Horticultural Society. Yellowing may result from waterlogged soil, especially if it’s clay-based. To remedy this, dig up the plants and eliminate any decaying or dead roots. Additionally, trim your boxwood to remove the affected upper growth. These hedge shears from Amazon are perfect for this task. Afterward, replant in a more suitable location that offers shelter from harsh winds, or in fresh compost mixed with grit to enhance drainage. If your boxwood is in pots, adjust your watering schedule and ensure there are drainage holes at the bottom of the containers.
The tips of the leaves can also yellow due to low temperatures. Frost damage might cause new growth to become pale brown and papery. In this case, replanting isn’t necessary, but you can prune affected areas in the spring. Applying fertilizer afterward will help revive them and promote new green growth.
This coming fall, apply a thick layer of mulch around your boxwood, but avoid letting it touch the stem. This will help protect the plants throughout the colder months.
Prune discolored leaves caused by winter damage in spring.
2. Effects of High Temperatures
Excessive heat and direct sunlight can also lead to yellow or orange leaves on boxwood. While established plants handle drought better, they still benefit from regular watering during particularly dry spells.
For boxwood in container gardens and younger shrubs, ensure you water them frequently, but be careful not to saturate the soil.
Keep boxwood balls in containers well-watered.
3. Box Blight
If you notice yellow leaves accompanied by dead brown patches, your shrub might be suffering from box blight. You may also observe black streaks on the stems.
John Negus, a garden journalist with over 50 years of experience, explains that box blight, if left untreated, can destroy the entire bush. Two fungi, Cylindrocladium buxicola and Volutella Buxi, are often the culprits.
“Prune back infected shoots to healthy tissue and dispose of the cuttings properly,” advises the expert. They recommend treating the plant with a fungicide designed for ornamental plants, which can help control the spread of the disease. Additionally, fertilizing the evergreen shrub can aid in its recovery — John suggests using sulfate of potash monthly from mid-spring until fall. Simply sprinkle it over the root area and water it in.
“If these actions don’t manage the disease, I recommend removing the entire bush, including roots and surrounding soil,” warns the team.
Box blight is a common issue, but prompt action can resolve it.
4. Caterpillars and Other Pests
Caterpillars can infest boxwood, causing the leaves to turn pale yellow or brown before wilting.
“The most effective way to tackle these pests is to hand-pick them and set up box tree moth traps,” John advises. These traps utilize pheromones to attract male moths, preventing fertilization of female eggs.
Boxwood leafminer can also be problematic, leading to yellowing leaves and a blistered appearance. Some boxwood varieties are more resistant than others, and spring pruning along with pesticides can help mitigate their damage.
