Caring for Common Lilac

Common lilac has low water needs once established. Water newly planted shrubs regularly through their first growing season—weekly in dry spells—to help roots settle in. After that, lilacs are remarkably drought-tolerant and usually need watering only during prolonged summer droughts. Overwatering or poorly drained soil can lead to root rot, so err on the dry side. Feed once a year in March with a balanced general-purpose fertiliser (such as blood, fish and bone or Growmore) scattered around the base at the rate recommended on the packet. Alternatively, apply a 5 cm layer of well-rotted compost or manure as a mulch in early spring; this feeds the soil and suppresses weeds. Avoid high-nitrogen feeds, which promote leafy growth at the expense of flowers. Lilacs growing in chalky or alkaline soils rarely need additional feeding. Renew mulch annually in spring, keeping it a few centimetres clear of the stems to prevent collar rot. In autumn, rake up and bin fallen leaves if powdery mildew has been a problem; this reduces overwintering spores. Common lilac is fully hardy across temperate Europe and needs no winter protection. Pests are few: lilac leaf miner can cause brown blotches on foliage in summer, but damage is cosmetic and rarely serious. Powdery mildew may appear as a white coating on leaves in dry summers, especially on plants in shade or crowded positions; improve air flow by thinning congested growth and avoid overhead watering. Lilac blight (bacterial disease) causes blackened shoots; prune out affected growth promptly and disinfect tools afterwards.