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Yak rhododendron

Rhododendron yakushimanum · Ericaceae

Yak rhododendron (Rhododendron yakushimanum) in flower
Photo: Daderot, via Wikimedia Commons (CC0)

A dense, low dome of dark leaves that are felted fawn-brown beneath and silvery when new, with rose-pink buds that open to apple-blossom flowers and fade to white.

Size
3½ ft tall, 4 ft wide
Zones
5 to 8
Light
Part sun to part shade
Flowers
Mid May to early June
Pets
Toxic (severe)
Job in a bed
Anchor

A bed built around yak rhododendron

The planner designed this bed around yak rhododendron when this page was made: a 16 × 8 ft (4.9 × 2.4 m) English border in zone 6, part sun. It chose the other plants from the 708 that suit those conditions, and says below why yak rhododendron stands where it does.

A 16 × 8 ft (4.9 × 2.4 m) bed at eye level in late May: Yak rhododendron, Green-and-gold, Bloody cranesbill 'Max Frei', White mugwort, Swamp milkweed, Tussock sedge, Winter heath 'Kramer's Red', Easter lily, Camassia, Poet's daffodil.
A 16 × 8 ft (4.9 × 2.4 m) English border in zone 6, part sun, seen from the path in late May.
4. White mugwort44. White mugwort44. White mugwort45. Swamp milkweed55. Swamp milkweed55. Swamp milkweed51. Yak rhododendron12. Green-and-gold22. Green-and-gold22. Green-and-gold22. Green-and-gold22. Green-and-gold23. Bloody cranesbill 'Max Frei'33. Bloody cranesbill 'Max Frei'33. Bloody cranesbill 'Max Frei'33. Bloody cranesbill 'Max Frei'33. Bloody cranesbill 'Max Frei'32. Green-and-gold22. Green-and-gold22. Green-and-gold23. Bloody cranesbill 'Max Frei'33. Bloody cranesbill 'Max Frei'33. Bloody cranesbill 'Max Frei'33. Bloody cranesbill 'Max Frei'34. White mugwort45. Swamp milkweed58. Easter lily88. Easter lily88. Easter lily89. Camassia99. Camassia99. Camassia97. Winter heath 'Kramer's Red'77. Winter heath 'Kramer's Red'77. Winter heath 'Kramer's Red'76. Tussock sedge66. Tussock sedge66. Tussock sedge62. Green-and-gold22. Green-and-gold22. Green-and-gold22. Green-and-gold22. Green-and-gold22. Green-and-gold22. Green-and-gold22. Green-and-gold22. Green-and-gold22. Green-and-gold29. Camassia99. Camassia910. Poet's daffodil10. Poet's daffodil10. Poet's daffodil10. Poet's daffodil10. Poet's daffodil10. Poet's daffodil10. Poet's daffodil10. Poet's daffodil
From above, to scale. Each circle is one plant, as wide as the room it needs.

The plants

  1. 1 Yak rhododendron × 1, pink
  2. 2 Green-and-gold × 18, yellow
  3. 3 Bloody cranesbill 'Max Frei' × 9, pink
  4. 4 White mugwort × 4, cream
  5. 5 Swamp milkweed × 4, white
  6. 6 Tussock sedge × 3, green leaves
  7. 7 Winter heath 'Kramer's Red' × 3, pink
  8. 8 Easter lily × 3, white
  9. 9 Camassia × 5, blue
  10. 10 Poet's daffodil × 8, white

Why this plant

  • The only dense clusters. The others are daisies, open bowls, plumes 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 tussock sedge and winter heath 'Kramer's Red'.

Why here

  • At the back, and only just seen. At 3½ ft it is about the height of Easter lily (3 ft) in front of it.
  • A step in the back row. Next to white mugwort (5 ft) and swamp milkweed (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 mid May to early June.
  • Part of the bed's peak. With green-and-gold, bloody cranesbill 'Max Frei', camassia and others in late May: 5 kinds at once. No week has more.
  • One of two evergreens. They are what the bed has to show from November to March.

Planned as an English border: 8 of the 9 groups (89%) are drifts, longer along the bed than they are deep. Green-and-gold is planted in four places along the bed, which gives it rhythm. The most in flower at one time is 5 kinds, from late May. Every line of the Design check comes out Good or better.

The planner's own design check: 11 Excellent, 6 Good.

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

Where yak rhododendron goes in a border

At 3½ ft it belongs at the back of a bed. In the planner's ten height classes it is moderately tall (3 to 4 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 neatest rhododendron, and handsome in leaf in every month. It keeps a tidy dome without pruning, so it suits a small bed where the big hybrids would not fit.

  • A compact rhododendron for small gardens
  • Foliage interest all year
  • Acid, part-shaded beds

What to plant with yak rhododendron

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

  • Hosta 'Halcyon': its blue-green leaves are a setting for the flowers, before and after; bold leaves against its medium ones; spires rising out of its mound.
  • Japanese painted fern: its silver leaves are a setting for the flowers, before and after; low enough (18 in) to stand in front of it; 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.

Questions about yak rhododendron

Does yak rhododendron need sun or shade?

Yak rhododendron 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 yak rhododendron grow in?

USDA zones 5 to 8. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).

Above zone 8 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 yak rhododendron flower in my zone?

In zone 5 it flowers mid May to early 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 yak rhododendron is in flower
Zone 5Mid May to early June
Zone 6Early May to early June
Zone 7Early May to late May
Zone 8Late April to late 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 yak rhododendron be planted?

3½ ft (100 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 4 ft (120 cm), so a group knits into one patch.

It grows 3½ ft (100 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.

How many yak rhododendron plants do I need?

At 3½ ft apart, set out in staggered rows:

  • 1 to fill 10 square feet (about 1 m²)
  • 4 for a single row 10 ft (3 m) long
  • 3 to fill a 4 × 8 ft bed on its own

In a mixed border, plant it as one, planted singly: it is the bed's structure, and everything else is arranged around it.

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

Is yak rhododendron 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 yak rhododendron?

They may. NC State does not list it as resistant to deer or rabbits. Where they visit, protect it, or plant it among ones they avoid.

What flowers after yak rhododendron?

Yak rhododendron is over by early June. These start as it finishes and carry the same spot on, so it never goes flat:

  • Daylily: from late June to early August, 2½ ft tall, to stand in front of it and cover its fading stems.
  • Astilbe: from late June to mid July, 24 in tall, to stand in front of it and cover its fading stems.
  • Bee balm: from early July to early August, 3 ft tall.

What does yak rhododendron look like in winter?

Yak rhododendron keeps its dark green leaves all winter, so it is one of the plants that hold a bed together from November to March, when the perennials have gone.

Is yak rhododendron good for bees and butterflies?

Yak rhododendron is visited by pollinators and specialist bees.

More Rhododendron

In these guides

Zone guides: Zone 5 · Zone 6 · Zone 7 · Zone 8

In flower in: May · June

Every fact on record

Type
Shrub
Size
3½ ft (100 cm) tall, 4 ft (120 cm) wide
Plant
3½ ft (100 cm) apart
Height class
Moderately tall (3 to 4 ft)
Place in the bed
Back
Flowers
Mid May to early June; dense clusters; pink, white
Leaves
Medium texture, evergreen; dark green
Shape
Mounding, clumping
Hardy in
USDA zones 5 to 8
Light
Part sun, part shade
Soil
Rich, evenly moist
Water
Moderate
Feeding
Light, in spring
Family
Ericaceae
Comes from
Japan
Attracts
Pollinators, specialist bees

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.