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Flame azalea

Rhododendron calendulaceum · Ericaceae

Flame azalea (Rhododendron calendulaceum) in flower
Photo: Daderot, via Wikimedia Commons (CC0)

A native azalea of the Appalachian mountains, with large clusters of flowers in blazing orange, gold or scarlet in late spring, as the leaves unfold.

Size
8 ft tall, 8 ft wide
Zones
5 to 7
Light
Part sun to part shade
Flowers
Mid May to mid June
Pets
Toxic (severe)
Job in a bed
Anchor

A bed built around flame azalea

The planner designed this bed around flame 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 flame azalea stands where it does.

A 22 × 10 ft (6.7 × 3.0 m) bed at eye level in late May: Flame azalea, Bloody cranesbill 'Max Frei', Creeping mahonia, White mugwort, Brown-eyed Susan, Lady's mantle, Carpathian bellflower 'Blue Clips', Sweet violet, Hosta 'Liberty', Turk's cap lily, Camassia, Easter lily.
A 22 × 10 ft (6.7 × 3.0 m) English border in zone 6, part sun, seen from the path in late May.
1. Flame azalea110. Turk's cap lily1010. Turk's cap lily1010. Turk's cap lily109. Hosta 'Liberty'93. Creeping mahonia33. Creeping mahonia33. Creeping mahonia32. Bloody cranesbill 'Max Frei'22. Bloody cranesbill 'Max Frei'22. Bloody cranesbill 'Max Frei'28. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet87. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'72. Bloody cranesbill 'Max Frei'22. Bloody cranesbill 'Max Frei'22. Bloody cranesbill 'Max Frei'22. Bloody cranesbill 'Max Frei'22. Bloody cranesbill 'Max Frei'27. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'75. Brown-eyed Susan55. Brown-eyed Susan55. Brown-eyed Susan54. White mugwort44. White mugwort44. White mugwort45. Brown-eyed Susan55. Brown-eyed Susan55. Brown-eyed Susan55. Brown-eyed Susan55. Brown-eyed Susan510. Turk's cap lily1010. Turk's cap lily1010. Turk's cap lily1012. Easter lily1212. Easter lily1212. Easter lily1212. Easter lily1211. Camassia1111. Camassia1111. Camassia1111. Camassia118. Sweet violet88. Sweet violet88. Sweet violet87. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'78. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet87. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'77. Carpathian bellflower 'Blue Clips'72. Bloody cranesbill 'Max Frei'22. Bloody cranesbill 'Max Frei'22. Bloody cranesbill 'Max Frei'22. Bloody cranesbill 'Max Frei'22. Bloody cranesbill 'Max Frei'23. Creeping mahonia33. Creeping mahonia33. Creeping mahonia33. Creeping mahonia33. Creeping mahonia36. Lady's mantle66. Lady's mantle66. Lady's mantle64. White mugwort48. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet88. Sweet violet811. Camassia1111. Camassia11
From above, to scale. Each circle is one plant, as wide as the room it needs.

The plants

  1. 2 Bloody cranesbill 'Max Frei' × 13, pink
  2. 3 Creeping mahonia × 8, yellow
  3. 4 White mugwort × 4, cream
  4. 5 Brown-eyed Susan × 8, yellow
  5. 6 Lady's mantle × 3, green
  6. 7 Carpathian bellflower 'Blue Clips' × 16, blue
  7. 8 Sweet violet × 59, purple
  8. 9 Hosta 'Liberty' × 1, dark green leaves
  9. 10 Turk's cap lily × 6, orange
  10. 11 Camassia × 6, white
  11. 12 Easter lily × 4, white

Why this plant

  • Part of the bed's structure. Shrubs and grasses keep their shape when the perennials die down. So does creeping mahonia.

Why here

  • Anchors a back corner. At 8 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 Turk's cap lily (6 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 five weeks. From mid May to mid June.
  • In company. With bloody cranesbill 'Max Frei', lady's mantle and camassia in late May: 4 kinds at once.

Planned as an English border: 15 of the 15 groups (100%) are drifts, longer along the bed than they are deep. The bed is balanced: the left half carries 52% of the visual weight and the right half 48%. The flowering is at its height in early August, with 5 kinds out together.

The planner's own design check: 10 Excellent, 6 Good, 1 Satisfactory.

Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.

Where flame azalea goes in a border

At 8 ft it belongs at the back of a bed. In the planner's ten height classes it is super tall (over 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.

The colour is as hot as any flower and glows in light shade. Give it acid, leafy, well-drained soil and a cool site. The upright, open habit leaves room beneath for ferns.

  • Brilliant colour at a woodland edge
  • Native woodland gardens
  • With mountain laurel and ferns

What to plant with flame azalea

Plants recorded as good partners for it, and what each pairing does:

  • Mountain laurel: in flower together for three weeks, from late May; happy in the same moist soil.
  • Christmas fern: its dark green leaves are a setting for the flowers, before and after; low enough (20 in) to stand in front of it.
  • Hosta: its green leaves are a setting for the flowers, before and after; bold leaves against its medium ones; low enough (18 in) to stand in front of it.

Questions about flame azalea

Does flame azalea need sun or shade?

Flame 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 flame azalea grow in?

USDA zones 5 to 7. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °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 flame azalea flower in my zone?

In zone 5 it flowers mid May to mid June. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.

Roughly when flame azalea is in flower
Zone 5Mid May to mid June
Zone 6Early May to mid June
Zone 7Early May to early June

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 flame azalea be planted?

6½ ft (200 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 8 ft (250 cm), so a group knits into one patch.

It grows 8 ft (250 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.

How many flame azalea plants do I need?

Usually one. At 6½ ft (200 cm) across, it is a plant you place, not one you mass. For a hedge or screen, set them 6½ ft apart: two plants for a 10 ft run.

In the bed above, the planner used one in one group.

Is flame 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.

Is there a pet-safe plant like flame azalea?

These come closest to doing what flame azalea does, and no toxicity is recorded for them:

  • Red osier dogwood: the same job in a bed, the same size and the same flowering time; white, not orange.
  • Redvein enkianthus: the same job in a bed and the same flowering time; 20 in taller, 20 in narrower.
  • Large fothergilla: the same job in a bed; 8 in narrower, flowers late April to mid May.

Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.

Do deer eat flame 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 flame azalea?

Flame azalea is over by mid June. These start as it finishes and carry the same spot on, so it never goes flat:

What does flame azalea look like in winter?

Flame 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 flame azalea good for bees and butterflies?

Flame azalea is visited by pollinators, bees, specialist bees, butterflies and hummingbirds.

It is native to the United States.

More Rhododendron

In these guides

Zone guides: Zone 5 · Zone 6 · Zone 7

In flower in: May · June

Every fact on record

Type
Shrub
Size
8 ft (250 cm) tall, 8 ft (250 cm) wide
Plant
6½ ft (200 cm) apart
Height class
Super tall (over 6½ ft)
Place in the bed
Back
Flowers
Mid May to mid June; dense clusters; orange, yellow, red
Leaves
Medium texture, deciduous; green
Shape
Upright, clumping
Hardy in
USDA zones 5 to 7
Light
Part sun, part shade
Soil
Rich, evenly moist
Water
Moderate
Feeding
Light, in spring
Family
Ericaceae
Comes from
Eastern Appalachians, U.S.A
Attracts
Pollinators, bees, specialist bees, butterflies, hummingbirds
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.