Viburnum

Rhododendrons are magnificent evergreen shrubs that produce enormous trusses of flowers in spring — from delicate whites and pinks to vivid reds, purples, and even yellows. They're woodland plants that thrive in dappled shade, acidic soil (pH 4.5–6.0), and sheltered conditions. On neutral or alkaline soil, they simply won't thrive — the leaves turn yellow (chlorosis) and the plant slowly declines. In such conditions, grow compact varieties in large containers filled with ericaceous compost, watered with rainwater. 'Cunningham's White' and 'Christmas Cheer' are among the hardiest large hybrids. For smaller gardens, the 'yakushimanum' hybrids are compact, dome-shaped, and incredibly floriferous. Deadheading after flowering (snap off the spent flower trusses carefully, without damaging the new growth buds beneath) improves flowering the following year. Rhododendrons have shallow root systems — mulch annually with leaf mould or bark to keep the roots cool and moist.

Holly is one of Britain's most iconic native evergreens — its glossy, spiny leaves and bright red berries are synonymous with Christmas. It makes an excellent hedging plant (dense, spiny, and virtually impenetrable to intruders) and a fine specimen tree. Holly is dioecious, meaning you need both male and female plants for berries — the female produces the berries, but only if a male is nearby for pollination. Confusingly, some varieties have misleading names: 'Golden King' is female (with berries) and 'Golden Queen' is male. 'J.C. van Tol' is a useful almost self-fertile variety. Holly tolerates heavy shade, pollution, coastal exposure, and most soil types — it's one of the toughest plants in the British garden. It can be pruned hard and topiarised into shapes. The berries provide vital winter food for birds, particularly thrushes and waxwings. Holly grows slowly, so buy the largest plant you can afford for hedging purposes.

Hydrangeas are among the most popular garden shrubs in the UK, valued for their enormous, long-lasting flower heads in shades of blue, pink, purple, and white. The flower colour of mophead (Hortensia) and lacecap types is famously influenced by soil pH: in acidic soil (below pH 5.5) they produce blue flowers; in alkaline soil, pink. To keep blue flowers blue, add aluminium sulphate or use ericaceous compost; to keep pink flowers pink, add lime. White varieties stay white regardless. 'Nikko Blue' and 'Endless Summer' are popular blue varieties; 'Madame Emile Mouillère' is the best white. Hydrangeas prefer partial shade — hot afternoon sun scorches the leaves and flowers. They need consistently moist soil and will wilt dramatically in drought (though they recover quickly after watering). Prune mophead and lacecap types in spring by cutting just above the first pair of healthy buds below last year's flower head. The dried flower heads provide winter structure — leave them on until spring.

Azaleas are essentially compact, often deciduous rhododendrons that produce an astonishing abundance of flowers in spring. The deciduous types (Mollis and Knap Hill hybrids) are particularly spectacular, covering themselves in flowers before the leaves emerge, and many offer superb autumn foliage colour too — giving you two seasons of interest. They share the same acidic soil requirement as rhododendrons (pH 4.5–6.0), and on alkaline soil must be grown in containers of ericaceous compost watered with rainwater. Japanese azaleas are evergreen, compact, and incredibly floriferous — 'Palestrina' (white) and 'Hino Crimson' (red) are classics. They're shade-tolerant and perfect for underplanting beneath trees. Azaleas have shallow root systems, so mulch annually and don't cultivate around them. They need very little pruning — just remove dead wood and shape lightly after flowering if necessary. Feed with an ericaceous fertiliser in spring.