Azalea

Rhododendron spp. (incl. R. simsii) · Tree/Shrub

Quick answer: Water: Deeply, when the top is dry; when the top few inches are dry, water deeply to 6–8 in. Light: Filtered or part shade; morning sun, shade after early afternoon. Soil: Acid, well-drained, rich in organic matter, pH 4.5–6.0. Pets: ASPCA lists azalea as toxic to cats and dogs; it contains grayanotoxins and can cause vomiting, diarrhea, weakness and heart problems. Keep pets away from leaves and flowers; if one has eaten any, call your vet promptly.

A spring-flowering shrub that covers itself in blooms. Garden azaleas want acid soil, filtered shade and steady moisture; the potted florist azalea (Rhododendron simsii) sold in winter is frost-tender and is usually kept as a cool, bright houseplant.

Care at a glance

Light

Filtered or part shade; morning sun, shade after early afternoon

Water

When the top few inches are dry, water deeply to 6–8 in

Soil

Acid, well-drained, rich in organic matter, pH 4.5–6.0

Temperature

Florist types are frost-tender; keep above 40 °F (estimated)

Spacing

3–4 ft apart in the garden

Container

At least 12 in wide, acid potting mix (estimated)

Bloom

Early spring to midsummer, depending on variety

Lifespan

Long-lived shrub, many years (estimated)

When?

Plant garden azaleas in spring or autumn when the soil is workable (estimated). Test the soil first and adjust pH from the results. Potted florist azaleas bought in winter stay indoors in a cool, bright room until spring.

Step by step

1. Test the soil; azaleas want pH 4.5–6.0 and fail in alkaline soil.
2. Check drainage: if water in a 6 in hole has not drained in 4 hours, build a raised bed.
3. Set the root ball about 2 in above the surrounding soil; never plant deeper than it grew in the pot.
4. Space plants 3–4 ft apart and mix plenty of composted pine bark or leaf mold into the bed.
5. Spread 2–3 in of mulch, keeping it a couple of inches from the stem.
6. In dry spells water deeply; the first summer on sandy soil may need it twice a week.
7. Prune right after spring flowering and stop pinching by July so next year's buds can form.
8. Feed only with a product for acid-loving plants, as the label says, in late spring; never in late autumn.

Common problems

Pets

ASPCA lists azalea as toxic to cats and dogs; it contains grayanotoxins and can cause vomiting, diarrhea, weakness and heart problems. Keep pets away from leaves and flowers; if one has eaten any, call your vet promptly.

Related tools

Similar plants