Smooth Hydrangea in April: monthly care

Smooth hydrangea 'Annabelle' thrives in partial shade or full sun, though in hotter spots some afternoon shade helps prevent the large white blooms from scorching. Choose a sheltered position if possible, as the heavy flower heads can be damaged by strong winds. The soil should be moisture-retentive loam or clay; this hydrangea dislikes dry conditions, so avoid free-draining sandy soils unless you're prepared to water frequently. Plant in March, April, September, or October when the soil is workable and not waterlogged. Dig a hole twice the width of the root ball and roughly the same depth. Break up any compacted soil at the base and incorporate a generous amount of well-rotted compost or manure to improve moisture retention. Position the plant so the top of the root ball sits level with the surrounding soil—planting too deep can lead to stem rot. Space plants 120 cm apart if you're creating a hedge or group planting; 'Annabelle' will reach 100–150 cm in both height and spread, so give it room to develop its natural rounded shape. After planting, backfill with the excavated soil mixed with compost, firm gently with your heel to eliminate air pockets, then water thoroughly. Apply a 5–8 cm layer of organic mulch such as composted bark or leaf mould around the base, keeping it a few centimetres clear of the stems. This mulch conserves moisture and suppresses weeds. Water again if the weather is dry over the following fortnight to help establishment.

Smooth hydrangea 'Annabelle' has high water needs, especially during dry spells in spring and summer when it's producing foliage and flowers. Water deeply once or twice a week in dry weather, soaking the root zone rather than sprinkling lightly. Mulch helps retain moisture, so top up the organic mulch layer each spring if it has broken down. In autumn and winter, rainfall is usually sufficient, but check containerised plants or those under eaves. Feed in March with a general-purpose balanced fertiliser such as blood, fish and bone, scattering a handful around the base and lightly forking it in. Apply a second feed in April as growth accelerates, then a final dose in June to support flowering. Avoid high-nitrogen feeds after midsummer, as they promote soft growth vulnerable to frost. 'Annabelle' is fully hardy (zone 3a–9a) and needs no special winter protection in temperate Europe. The stems die back naturally or can be left standing for winter interest, then pruned away in March. Pests are rarely a problem, though aphids occasionally cluster on soft new shoots in spring—a strong jet of water or insecticidal soap deals with them. Powdery mildew can appear on the foliage in dry summers, especially if the roots are stressed; ensure consistent watering and avoid overhead watering late in the day. Leaf spot may occur in wet seasons but is usually cosmetic. Remove and bin affected leaves, and improve air circulation by thinning congested growth during the annual prune.