Royal azalea
Rhododendron schlippenbachii · Ericaceae
Large, flat, soft pink flowers, freckled with brown, open with the unfolding leaves, which are broad, set in whorls of five, and turn yellow, orange and crimson in autumn.
- Size
- 6½ ft tall, 6½ ft wide
- Zones
- 4 to 7
- Light
- Part sun to part shade
- Flowers
- Early May to late May
- Pets
- Toxic (severe)
- Job in a bed
- Anchor
A bed built around royal azalea
The planner designed this bed around royal azalea when this page was made: a 22 × 10 ft (6.7 × 3.0 m) English border in zone 6, part sun. It chose the other plants from the 708 that suit those conditions, and says below why royal azalea stands where it does.
The plants
- 1 Royal azalea × 1, pink
- 2 Leadwort × 16, blue
- 3 Mouse-ear coreopsis 'Nana' × 21, yellow
- 4 Elderberry 'Lemony Lace' × 1, chartreuse leaves
- 5 Joe Pye weed 'Little Joe' × 4, pink
- 6 White mugwort × 3, cream
- 7 Boxwood 'Green Gem' × 3, dark green leaves
- 8 Black-eyed Susan × 3, yellow
- 9 Bee balm 'Purple Rooster' × 3, purple
- 10 Lady's mantle × 5, green
- 11 Woodland stonecrop × 56, white
- 12 Asiatic lily × 5, orange
- 13 Easter lily × 4, white
- 14 Sicilian honey garlic × 6, cream
Why this plant
- The only open bowls. The others are dense clusters, daisies, flat plates and others. Shape reads at a distance, where colours blur.
- Part of the bed's structure. Shrubs and grasses keep their shape when the perennials die down. So do elderberry 'Lemony Lace' and boxwood 'Green Gem'.
Why here
- Anchors a back corner. At 6½ ft it is the tallest plant here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to Joe Pye weed 'Little Joe' (4 ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- One plant, alone. A shrub is seen as an object, and needs clear ground around it.
Why now
- In flower for four weeks. From early May to late May.
- In company. With mouse-ear coreopsis 'Nana', woodland stonecrop and Sicilian honey garlic in late May: 4 kinds at once.
Planned as an English border: 15 of the 18 groups (83%) are drifts, longer along the bed than they are deep. Elderberry 'Lemony Lace' and boxwood 'Green Gem' are grown for their leaves rather than their flowers. The bed is tied together by its repeats: four kinds come round again along it, among them woodland stonecrop and mouse-ear coreopsis 'Nana'.
The planner's own design check: 12 Excellent, 5 Good.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where royal azalea goes in a border
At 6½ ft it belongs at the back of a bed. In the planner's ten height classes it is very tall (5 to 6½ ft).
Its job: anchor. A shrub that gives the bed permanent structure. Planted singly, as soon as the front edge is laid; everything else is arranged around it.
Many gardeners rank it the most beautiful of all azaleas. It has good form, scent and autumn colour, and tolerates less acid soil than most.
- A specimen azalea for a woodland garden
- Autumn colour
- Soft pink in spring
What to plant with royal azalea
Plants recorded as good partners for it, and what each pairing does:
- Japanese forest grass: its green leaves are a setting for the flowers, before and after; fine leaves against its bold ones; low enough (18 in) to stand in front of it.
- Virginia bluebells: in flower together for two weeks, from early May; medium leaves against its bold ones; low enough (20 in) to stand in front of it.
- Christmas fern: its dark green leaves are a setting for the flowers, before and after; medium leaves against its bold ones; low enough (20 in) to stand in front of it.
Questions about royal azalea
Does royal azalea need sun or shade?
Royal azalea grows in part sun (4 to 6 hours of sun, including some afternoon sun) and part shade (2 to 4 hours of sun, mostly in the morning).
It wants soil that stays evenly moist, rich in organic matter, and a good soak in dry spells.
What zones does royal azalea grow in?
USDA zones 4 to 7. It is hardy to zone 4, which means it survives winter nights down to about −20 °F (−29 °C).
Above zone 7 it struggles: the zones measure winter cold, but a plant's top zone usually means the summers are too hot or the winters too mild for it to rest.
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does royal azalea flower in my zone?
In zone 5 it flowers early May to late May. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 4 | Early May to late May |
|---|---|
| Zone 5 | Early May to late May |
| Zone 6 | Late April to mid May |
| Zone 7 | Mid April to early May |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should royal azalea be planted?
6 ft (180 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 6½ ft (200 cm), so a group knits into one patch.
It grows 6½ ft (200 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many royal azalea plants do I need?
Usually one. At 6 ft (180 cm) across, it is a plant you place, not one you mass. For a hedge or screen, set them 6 ft apart: two plants for a 10 ft run.
In the bed above, the planner used one in one group.
Is royal azalea poisonous to dogs and cats?
Yes: severe toxicity to people, dogs, cats and horses. All parts, including the nectar, are highly poisonous if eaten and can affect the heart.
Rated from NC State Extension and the ASPCA. Where references disagree, the more cautious rating is used.
Do deer eat royal azalea?
Mostly not. NC State lists it as resistant to rabbits. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.
What flowers after royal azalea?
Royal azalea is over by late May. These start as it finishes and carry the same spot on, so it never goes flat:
- Blue false indigo: from late May to mid June, 4 ft tall, to stand in front of it and cover its fading stems.
- Foxglove: from early June to mid July, 4 ft tall, to stand in front of it and cover its fading stems.
- Feather reed grass 'Karl Foerster': from late June to early October, 5 ft tall, to stand in front of it and cover its fading stems.
What does royal azalea look like in winter?
Royal azalea drops its leaves and stands as bare branches. That is when to see its shape, and to prune it if it needs pruning.
Is royal azalea good for bees and butterflies?
Royal azalea is visited by pollinators, specialist bees and butterflies.
More Rhododendron
- Azalea 'Delaware Valley White' Rhododendron 'Delaware Valley White'
- Azalea 'Hino-Crimson' Rhododendron 'Hino-Crimson'
- Catawba rhododendron Rhododendron catawbiense
- Evergreen azalea Rhododendron (Kurume hybrids)
- Flame azalea Rhododendron calendulaceum
- Korean rhododendron 'Cornell Pink' Rhododendron mucronulatum 'Cornell Pink'
- Northern Lights azalea Rhododendron (Northern Lights Group)
- Pinxterbloom azalea Rhododendron periclymenoides
- Reblooming azalea Rhododendron (Encore Group)
- Rhododendron 'Cunningham's White' Rhododendron 'Cunningham's White'
- Rhododendron 'Nova Zembla' Rhododendron 'Nova Zembla'
- Rhododendron 'Olga Mezitt' Rhododendron 'Olga Mezitt'
- Rhododendron 'PJM' Rhododendron 'PJM'
- Rhododendron 'Purple Gem' Rhododendron 'Purple Gem'
- Rhododendron 'Roseum Elegans' Rhododendron 'Roseum Elegans'
- Rosebay rhododendron Rhododendron maximum
- Swamp azalea Rhododendron viscosum
- Yak rhododendron Rhododendron yakushimanum
In these guides
- Rabbit-resistant plants
- Garden plants toxic to cats
- Garden plants toxic to dogs
- Plants for butterflies
- Plants for bees
Zone guides: Zone 4 · Zone 5 · Zone 6 · Zone 7
In flower in: May
Every fact on record
- Type
- Shrub
- Size
- 6½ ft (200 cm) tall, 6½ ft (200 cm) wide
- Plant
- 6 ft (180 cm) apart
- Height class
- Very tall (5 to 6½ ft)
- Place in the bed
- Back
- Flowers
- Early May to late May; open bowls; pink
- Leaves
- Bold texture, deciduous; green
- Shape
- Rounded, clumping
- Hardy in
- USDA zones 4 to 7
- Light
- Part sun, part shade
- Soil
- Rich, evenly moist
- Water
- Moderate
- Feeding
- Light, in spring
- Family
- Ericaceae
- Comes from
- China, Japan, Korea
- Attracts
- Pollinators, specialist bees, butterflies
- Stands up to
- Rabbits
Checked against NC State Extension and ASPCA poison lists. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.