Rhododendron
Azaleas are rhododendrons — botanically the same genus, split in the garden by leaf and size rather than by family. What they share is the thing that decides whether you can grow them at all: they need acid soil, and on chalk or limestone they will yellow and sulk however well you feed them.
If your soil is wrong, a pot of ericaceous compost is not a compromise, it is the correct answer. Rainwater rather than tap water is the other half of it, especially in hard-water areas like London.
Care
Dappled light under high tree canopy is ideal; avoid full sun and cold, drying wind.
Shallow, fibrous roots dislike drying out.
Acidic, humus-rich, moisture-retentive but well-drained soil; essential to grow in ericaceous, peat-free compost in a pot on alkaline soil, as this genus cannot tolerate lime.
Minimal — deadhead spent flower trusses carefully, snapping them off without damaging the new growth bud just below. Overgrown plants tolerate hard renovation pruning, though it sacrifices flowers for a year or two.
An ericaceous feed after flowering and again in early summer while next year's buds form. Never use a general or lime-containing fertiliser: on these shallow roots it shows quickly as yellowing between the leaf veins.
Layering is the dependable home method — peg a low branch into leafy soil and leave it a year or two. Semi-ripe cuttings root only with a wounded base, hormone and bottom heat, and even then not reliably.
Month by month
Months change with the climate: in southern Italy tomatoes go out two months earlier than in England.
- AprilFeed with an ericaceous feed as flowering finishes. how ›
- MayDeadhead spent flower trusses carefully, avoiding the new growth bud beneath. how ›
- NovemberMulch with an acidic, peat-free mulch (composted bark or pine needles) to protect shallow roots. how ›
Months based on climate: UK. Your choice stays on this device.
- AprilFeed with an ericaceous feed as flowering finishes. how ›
- MayDeadhead spent flower trusses carefully, avoiding the new growth bud beneath. how ›
- NovemberMulch with an acidic, peat-free mulch (composted bark or pine needles) to protect shallow roots. how ›
Months based on climate: Northern Italy. Your choice stays on this device.
- MarchFeed with an ericaceous feed as flowering finishes. how ›
- AprilDeadhead spent flower trusses carefully, avoiding the new growth bud beneath. how ›
- NovemberMulch with an acidic, peat-free mulch (composted bark or pine needles) to protect shallow roots. how ›
Months based on climate: Central Italy. Your choice stays on this device.
- MarchFeed with an ericaceous feed as flowering finishes. how ›
- AprilDeadhead spent flower trusses carefully, avoiding the new growth bud beneath. how ›
- DecemberMulch with an acidic, peat-free mulch (composted bark or pine needles) to protect shallow roots. how ›
Months based on climate: Southern Italy and islands. Your choice stays on this device.
Common problems
How to spot it. On alkaline soil.
What to do. Move to a pot with ericaceous compost, or use a chelated iron tonic as a temporary fix.
How to spot it. Grubs feeding on roots, adults notching leaf edges.
What to do. Check compost, consider a nematode drench.
How to spot it. Browned, bristly buds that fail to open, associated with leafhopper damage.
What to do. Remove affected buds.
Popular varieties
Questions
Rhododendron: is it hardy?
H6: Hardy in the vast majority of UK gardens. It survives down to −20 °C.
Can it grow in a pot?
An excellent, often essential choice in a large pot with ericaceous compost on alkaline soil.
Rhododendron: when do you prune it?
Minimal — deadhead spent flower trusses carefully, snapping them off without damaging the new growth bud just below.
Rhododendron: when does it flower?
In the climate of UK it flowers in March–April.
When do you feed it?
An ericaceous feed after flowering and again in early summer while next year's buds form. Never use a general or lime-containing fertiliser: on these shallow roots it shows quickly as yellowing between the leaf veins. Feeding months, UK: April, June.