Rhododendron in April: monthly care

Rhododendrons thrive in partial to full shade, making them ideal for woodland gardens or north-facing borders where many other shrubs struggle. They require acidic soil with a pH between 4.5 and 6.0, so avoid planting in chalky or alkaline ground. If your soil is neutral or slightly alkaline, dig in generous amounts of ericaceous compost or peat substitute, or consider growing your rhododendron in a large container filled with ericaceous potting mix. Prepare the planting site by digging a hole twice as wide as the root ball but no deeper—rhododendrons have shallow, fibrous roots that sit close to the surface. Break up compacted soil at the base and sides of the hole to encourage drainage, as waterlogged roots will quickly rot. Mix plenty of organic matter such as leaf mould or composted bark into the excavated soil to improve structure and moisture retention. Plant in April, May, September or October when the soil is workable and temperatures are mild. Position the root ball so the top sits level with or very slightly above the surrounding soil—never bury the stem. Backfill with your amended soil, firming gently to eliminate air pockets. Space plants 240 cm apart to allow for their mature spread of up to 3 metres. Water thoroughly after planting, soaking the root zone completely. Apply a 5–8 cm layer of acidic mulch such as pine bark, composted conifer needles or leaf mould around the base, keeping it clear of the stem. This conserves moisture, suppresses weeds and gradually acidifies the soil as it breaks down. Avoid disturbing the soil around established plants, as their shallow roots are easily damaged.

Rhododendrons have moderate water needs but dislike both drought and waterlogging. Water regularly during dry spells from spring through autumn, especially in the first two years after planting. Aim to keep the root zone consistently moist but never saturated. In hot, dry summers, water deeply once or twice a week rather than little and often. Reduce watering in winter, but check evergreen foliage during prolonged dry spells—desiccation is a common cause of winter damage. Feed in March and again in April with a slow-release ericaceous fertiliser formulated for acid-loving plants. Scatter granules evenly around the base, avoiding direct contact with stems, and water in well. Never use general-purpose or high-nitrogen feeds, which can cause lush growth prone to frost damage and may raise soil pH over time. Refresh the mulch layer each spring with acidic organic matter to maintain soil acidity, suppress weeds and conserve moisture. Rhododendrons are evergreen and fully hardy in zones 5a–8b, so they need no special winter protection in temperate Europe, though young plants benefit from shelter from cold, drying winds. Watch for vine weevil, whose larvae chew roots and can kill plants; treat with biological nematodes in late summer. Rhododendron leaf hopper causes unsightly brown spots and spreads bud blast, a fungal disease that blackens flower buds—remove affected buds promptly and control hoppers with insecticide in late summer. Powdery mildew and rust occasionally affect foliage in humid conditions; improve air circulation and avoid overhead watering. Yellowing leaves (chlorosis) indicate alkaline soil or hard tap water—remedy with sequestered iron and rainwater where possible.