The most common reasons for boxwood turning yellow include:
- Winter weather damage, especially from waterlogged soil or frost injury, which can cause yellowing or browning of leaves. Winter burn is also a factor where cold exposure damages the foliage. Protecting boxwood with mulch and proper site selection can help prevent this.
- High temperatures and excessive sun exposure can cause stress leading to yellow or orange leaves, especially during drought. Proper watering and partial shade can alleviate this.
- Nutrient deficiency, particularly lack of iron or magnesium, often due to poor soil conditions or improper fertilization, can cause yellowing. Soil testing and adjustment, along with proper fertilization, can help.
- Diseases such as box blight, which causes yellow leaves with brown dead patches and black streaks on stems. Prompt pruning of infected parts and fungicide application are necessary.
- Root rot from fungal pathogens due to poor drainage, causing yellowing leaves and poor growth. Improving drainage and reducing watering helps.
- Pests like nematodes or spider mites feeding on roots or foliage can also cause yellowing.
Other possible causes include soil pH imbalance or salt damage from de-icing salts altering soil chemistry.
Proper diagnosis involves inspecting for pests or disease, checking soil moisture, testing soil nutrients and pH, and considering recent weather conditions. Treatment depends on the cause but includes improving drainage, adjusting watering, fertilizing, pruning infected parts, and protecting from harsh weather.
This comprehensive view should help understand why a boxwood might be turning yellow and guide toward solutions.
