Buxus sempervirens has a very shallow, wide-spreading root system. Soil around the base of box will be disturbed and removed overtime by weeding, watering and Winter weather conditions.
This may leave the root system exposed and at risk of drying out, which will affect the health of the box. A regular application of mulch every Spring is a good way to protect the roots and help retain moisture in the soil during the dry Summer months.
Mulching has also been shown to help in the battle against box blight. A stronger, healthier box plant shows greater resistance to blight infections. The mulch also reduces the risk of dispersing the blight fungal spores when watering.
Look for a mulch rich in organic matter. Homemade compost works well as long as it has reached hot enough temperatures to kill any nasty diseases or weed seeds. Mulches can be sourced online from good specialist suppliers that are guaranteed to be weed and disease free. I used to recommend mushroom compost but have been put off it recently when a Head Gardener told me of all the pesticides used in mushroom production. Organic mushroom compost could be ok but this is hard to find and expensive. Composted leaf mulch works well, especially for moisture retention but is not so good for providing important nutrients to the box plants.
Box are hungry plants and will really appreciate the nutritional value of a mulch rich in organic matter. The soil structure will also be improved, enhancing the box’s root system and encouraging stronger, healthier plants.