Shrub
Rhododendron
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Flowers | Flowers in April | Flowers in May | Flowers in June | |||||||||
| Plant | Plant in March | Plant in April | Plant in October | Plant in November | ||||||||
| Prune | Prune in June | |||||||||||
| Looks good | Looks good in April | Looks good in May | Looks good in June |
Overview
Rhododendrons range from dwarf alpine shrubs no taller than a footstool to woodland giants, and include the deciduous and evergreen azaleas. In late spring they are smothered in trusses of flowers in every shade except true blue. For small gardens, the Yakushimanum hybrids, such as 'Percy Wiseman', stay compact and have felted new leaves; 'Cunningham's White' is a tough old hybrid; and deciduous azaleas like 'Persil' add scent and autumn leaf colour. Avoid Rhododendron ponticum, which is invasive in parts of Britain and Ireland.
Where to grow rhododendron
Dappled shade and shelter from cold, drying winds suit most kinds, though small-leaved dwarf types take more sun. The soil must be acidic, moist and rich in organic matter. Test your soil first; on chalk or alkaline clay, leaves turn yellow and plants decline.
Planting
Plant in spring or autumn, with the top of the root ball level with or slightly above the soil; buried roots can suffocate. Dig in plenty of leaf mould or composted bark, and mulch afterwards. For pots, use ericaceous compost.
Care through the year
Spring
Feed with an ericaceous fertiliser as growth begins. Water in dry spells, using rainwater where possible.
Summer
Never let the roots dry out, as this is when next year's buds form. Top up the mulch.
Autumn
Plant new shrubs and refresh the mulch with pine needles, leaf mould or bark.
Winter
Protect pots from waterlogging and hard freezes. Shake heavy snow off branches.
Pruning
Little pruning is needed. Snap off spent flower trusses carefully after flowering, avoiding the new buds beneath. Overgrown hardy hybrids can be cut back hard in late winter, though flowering may pause for a year or two.
Propagation
Layering is the easiest home method: peg a low branch into the soil in spring and sever it once rooted, usually a year later. Semi-ripe cuttings are possible but slow without heat.
Common problems
Yellow leaves with green veins point to lime-induced chlorosis; switch to rainwater and acid feed or move plants into pots. Vine weevil adults notch leaf edges and grubs eat roots. Bud blast turns buds brown and bristly; remove affected buds. Phytophthora root rot affects plants in waterlogged ground.
Guides to the problems most likely to affect rhododendron:
Something else wrong? Diagnose it by symptom.
Month-by-month reminders
Jobs for this plant come round in March, April, June, October and November. Each month page lists everything else worth doing in the garden at the same time.
Related plants
Sources
Botanical names follow Kew's Plants of the World Online; growing attributes were checked against the references below. Text is our own. See our editorial policy.