Rosemary is borderline hardy in Zone 6b — it survives most winters against a south-facing wall with excellent drainage, but a wet cold snap can kill it outright. The safest approach: grow in a container and overwinter indoors on a sunny windowsill, or accept that you may need to replace it every few years. The flavour and fragrance are unmatched for roasting meats, potatoes, and infused oils.
Propagate from stem cuttings in summer — this is faster and more reliable than seed. Prune lightly after flowering, removing no more than one-third of growth at a time; rosemary does not regrow from old wood.
Powdery mildew
White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.
Root rot
Plants wilt, yellow, and stunt even in moist soil; lower stems and roots turn brown, soft, and mushy and the plant may collapse. Most common in heavy, wet, or poorly drained ground.
Improve drainage and stop overwatering, and never plant too deep. Lift and destroy badly affected plants along with the soil around the roots. Grow in raised or free-draining beds to prevent it returning.
Botrytis (grey mould)
Grey fuzzy mould on petals and stems, worst in cool wet conditions.
Remove affected parts immediately. Improve air circulation. Avoid overhead watering. Apply copper fungicide if severe.
Spider Mites
Tetranychus urticae →Fine stippling or bronzing on leaves, faint webbing on undersides, foliage drying out during hot, dry weather.
Spray foliage with a strong jet of water to dislodge mites. Apply insecticidal soap or horticultural oil to leaf undersides; repeat every 5–7 days as needed.