Azalea
Azaleas are compact rhododendrons that smother themselves in bloom in late spring — evergreen or deciduous, in near-fluorescent colours. They are not fussy so much as specific: they must have acid soil, dappled shade and roots that stay moist without ever sitting wet.
Seriously toxic to pets & livestock
Azaleas (Rhododendron) are seriously toxic. They contain grayanotoxins that disrupt heart and nerve function; even a few leaves can cause drooling, vomiting, weakness, collapse and — in larger amounts — dangerous heart-rhythm changes. This is a genuine hazard: keep all pets and livestock away, and call a vet urgently if any is eaten.
Care at a glance
Everything that matters, in six lines. The detail is further down.
Position
Light shade under high canopy is ideal. Shelter from cold winds and early sun on frosted buds; deep shade cuts flowering.
Water
Shallow-rooted and quick to wilt in dry spells. Water with rainwater — hard tap water raises the pH it can't tolerate.
Hardiness
Most are fully hardy, but shelter from cold, drying winds, and protect early flower buds from hard late frosts.
Soil
Must have acid (ericaceous) soil — ericaceous compost in pots. It will not tolerate lime or chalky ground at all.
Feeding
A feed formulated for ericaceous plants after flowering. Avoid ordinary lime-based feeds.
Flowering
A dense flush of blooms, followed by fresh growth. Deadhead spent trusses carefully by hand.
What to do, and when
Main flowering — deadhead spent trusses without damaging the new buds just below, then mulch with leaf mould or composted bark.
Keep the shallow roots cool and moist, watering with rainwater in dry spells, and give an ericaceous feed; next year's buds set now.
A good time to plant new shrubs; top up the mulch, and enjoy the fiery leaf colour on the deciduous kinds.
Dormant but evergreen types still lose water — shelter from cold winds, keep out of frost pockets, and never let it sit waterlogged.
It's all about acid soil
Azaleas are ericaceous: they can only take up nutrients in acid soil, roughly pH 4.5–6. On neutral or chalky ground the leaves yellow between green veins and the plant slowly starves, so grow them in acid beds or in pots of ericaceous compost.
Water matters as much as soil. Hard tap water is limey and pushes the pH up over time, so use rainwater wherever you can, especially for container plants, and mulch to keep the shallow roots cool and moist.
A genuinely poisonous shrub
Every part of an azalea contains grayanotoxins, which affect the heart and nervous system. Even a small amount eaten can make a dog, cat, horse or grazing animal seriously ill, so site it where pets and livestock can't browse it.
Wash your hands after pruning, don't burn the clippings where anyone breathes the smoke, and if an animal does eat any, treat it as an emergency and call a vet straight away.
Common problems
Yellow leaves with green veins
Lime-induced chlorosis from alkaline soil or hard water. Switch to rainwater, feed ericaceous, and grow in acid soil or a pot.
Wilting in summer
The shallow roots have dried out. Water deeply with rainwater and mulch to keep the root zone cool and moist.
Notched leaf edges, sudden collapse
Vine weevil — adults notch leaves, grubs eat the roots, worst in pots. Check the rootball and treat with nematodes.
Silvery, mottled leaves
Rhododendron leafhopper or lace bug, worse in hot, sunny sites. Improve shade and shelter; remove badly affected leaves.
Everything an azalea needs
Acid soil, dappled shade, rainwater — and a spot pets can't reach.
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Other plants with a similar temperament.
How we checked this
Care cross-checked against the RHS. Toxicity confirmed against the ASPCA database and project Tier A safety data, which list azalea (Rhododendron) as seriously toxic to cats, dogs, horses and livestock — grayanotoxins that can cause vomiting, weakness, collapse and dangerous heart-rhythm changes. If our page and these sources ever disagree, believe them — and tell us.
Sources: RHS · ASPCA — toxic & non-toxic plants
Last reviewed · July 2026