Caring for Rosemary

Rosemary is a low-maintenance herb once established, requiring little intervention beyond occasional watering during prolonged dry spells in summer. Even then, it tolerates drought well and prefers to be under-watered rather than over-watered. In winter, avoid watering altogether unless the plant is in a container and the compost has dried out completely. Overwatering, especially in heavy or poorly drained soil, is the most common cause of rosemary failure in temperate climates. Feeding is not necessary. Rosemary originates from the Mediterranean and thrives in poor, lean soils. Excessive fertility encourages soft, sappy growth that is more susceptible to frost and pests, and dilutes the aromatic oils in the foliage. If your plant looks pale or weak, the problem is more likely poor drainage or insufficient light rather than lack of nutrients. Rosemary is hardy in zones 7a–10b, but in colder or exposed gardens it benefits from a sheltered position against a south- or west-facing wall. In zone 7, a severe winter can damage or kill plants, especially if they sit in wet soil. Mulching around the base is not recommended, as it can trap moisture and encourage root rot. Container-grown rosemary can be moved under cover during the coldest months if space allows. Pests are rarely a problem, though rosemary beetle—a distinctive striped beetle—can defoliate plants in late summer and autumn. Pick off adults and larvae by hand or spray with an organic insecticide if the infestation is severe. Powdery mildew may appear in humid conditions or on overcrowded plants; improve air circulation by thinning growth and avoid overhead watering.