Boxwood can turn yellow due to nutrient deficiency, excess water, fungal diseases or excessive sun exposure.
Boxwoods often turn yellow due to pesky little critters like the boxwood moth, a voracious caterpillar that gnaws on the leaves in the blink of an eye. Another common parasite is mites, tiny spiders invisible to the naked eye that suck the sap, leaving yellowing and damaged leaves. It’s no better on the disease front, with nasty fungi like Cylindrocladium buxicola, responsible for the infamous "leaf wilt disease," which causes unsightly spots and rapid yellowing. These pests and diseases stress your boxwood, which eventually loses vigor and color.
Boxwoods do not tolerate sudden changes in temperature. Even short episodes of drought can quickly give them a dry and yellowish appearance. A winter that is too cold, with severe frost, burns the leaves that rapidly turn yellow and then brown. Conversely, prolonged heatwaves or drying winds exacerbate the loss of moisture from the leaves. In short, boxwoods do not cope well with extreme weather fluctuations, and this is often what causes them to turn yellow.
A yellowing boxwood may be lacking in essential nutrients, especially nitrogen or magnesium. When nitrogen is deficient, the leaves become pale and lose their beautiful green color. The same goes for magnesium; a deficiency leads to the appearance of yellow areas between the veins, giving a marbled look. Poor soil or soil that is regularly leached by rainwater often promotes this phenomenon. To address this, an appropriate application of fertilizer or organic amendments (compost, well-rotted manure) quickly gets things back on track.
When you prune too severely or at the wrong time, you put your boxwood under stress. As a result, it struggles to properly sprout new growth and its leaves turn yellow. Excessive pruning greatly reduces the leaf area, which decreases its ability to photosynthesize, leading to less energy for growth. Ideally, grab your pruners in the spring or late summer, but absolutely avoid very hot or very cold days. Also, remember to cut with well-sharpened and clean tools to avoid unnecessary injuries or the risk of infection.
Soil that is too compact or poorly aerated, like heavy or clayey soil, prevents boxwood roots from breathing properly. As a result, they suffocate, can rot, and the leaves quickly start to yellow. If the soil also retains standing water – due to poor drainage – the situation worsens even more quickly, as the excess water displaces the essential oxygen. Another common issue is soil that is too acidic or alkaline, meaning the pH is completely off from what boxwood prefers, leading to yellowing as well. In short: balanced, aerated soil without permanent puddles, or suffering boxwood!
The gradual yellowing of the leaves starting from the base of the boxwood may indicate overly compacted or poorly drained soil, an issue that can be resolved by adding coarse sand or organic matter to the soil.
Traditionally used for trimmed hedges and various topiaries, varieties of boxwood differ greatly in their sensitivity to stress, with some being more resistant to diseases than others.
The use of wood ash (rich in potash) can be beneficial for strengthening the resistance of boxwood and limiting the yellowing of its leaves.
The boxwood can live for several centuries if it grows in favorable conditions, and some historical specimens have even exceeded the age of 500 years.
Sure! Here is the translation: "Yes, depending on the cause of the yellowing. If the problem is correctly identified (pests, deficiencies, drainage issues), an appropriate treatment, along with sanitation pruning and fertilization, can allow the boxwood to gradually regain its vigor."
To prevent yellowing, choose a specific organic fertilizer for boxwood that is rich in nitrogen and magnesium, essential elements for maintaining lush green foliage.
No, yellowing is not necessarily due to a disease. It can also result from unfavorable weather conditions, a lack of nutrients, or a drainage problem in the soil.
It is advisable to trim the boxwood twice a year, ideally in the spring and late summer. However, be careful to avoid overly severe pruning or doing it at an inappropriate time, as this can cause stress to the plant and lead to yellowing.
To identify the boxwood moth, look for light green caterpillars with black striped patterns on your plants. You may also notice whitish webs and dark droppings accumulated on the leaves.
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