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Yaku Rhododendron Rhododendron yakushimanum

Other Common Name(s):

Previously known as:

  • R. metternichii var. yakushimanum
Phonetic Spelling
rho-do-DEN-dron ya-koo-shee-MAH-num
This plant has high severity poison characteristics.
See below
Description

Yaku rhododendron is a woody, evergreen shrub in the Ericaceae (blueberry) family and native to Japan. This compact plant grows slowly into a dense, rounded mound or dome 2 to 3 feet tall and wide, sometimes reaching a height and width of 9 feet. The genus name derives from the Greek words rhodo, which means rose, and dendron, meaning tree. The species name yakushimanum comes from the island of Yakushima where it is native.

Rhododendrons as a whole tend to do better in higher elevations with cooler temperatures. Plant in a location with partial to dappled shade and moist, acidic, well-drained, organically rich soils. It will suffer in hot southern summers and needs protection from afternoon sun though it tolerates sun better than other rhododendrons.

This shrub provides year-round interest with its thick, glossy and leathery, curled leaves with velvety brown hairs on the undersurface. New growth is covered in dense white hairs. Attractive dark-pink buds open to light-pink flowers that fade to white in mid-spring.   This plant tolerates browsing by rabbits.

Use this plant in a container as a houseplant or interiorscape or in the landscape at the back of a border as an understory, woody shrub in a woodland or natural area. It works well as a low hedge or planted in an Asian or pollinator garden where its flowers will attract bees and other pollinators. 

Insects, Diseases, and Other Plant Problems:  Insect problems include aphids, borers, lace bugs, leafhoppers, mealybugs, mites, nematodes, scale, thrips, and whitefly.  Diseases include canker, crown rot, root rot, leaf spot, rust, and powdery mildew.  This plant is frequently damaged by deer but tolerates browsing by rabbits. Early flowering makes it susceptible to spring freezes, especially if planted in sunny locations where leaves and flowers emerge early.

While these shrubs remain very popular for landscape use, many cultivars are susceptible to Phytophthora root rot—this leads to leaf loss, reduced vigor, branch dieback, and wilting. Implement good cultural practices first, such as improving drainage with organic matter or berms and avoiding overwatering or overfertilization. However, if you have a site with a history of this disease, consider planting one of the root rot-resistant alternative species listed in the left-hand sidebar. 

For suitable alternatives, see this video created by Charlotte Glen as part of the Plants, Pests, and Pathogens series.

 VIDEO Created by Elizabeth Meyer for "Trees, Shrubs and Conifers" a plant identification course offered in partnership with Longwood Gardens.

More information on Rhododendron.

Profile Video:
See this plant in the following landscape:
Cultivars / Varieties:
  • 'Crete'
    Magenta buds, rose pink flowers fade to white
  • 'Van Zile'
'Crete', 'Van Zile'
Tags:
#showy flowers#deciduous#poisonous#houseplant#wildlife plant#pink flowers#slow growing#nectar plant#velvety#interiorscape#low maintenance#fall interest#year-round interest#hedges#specialized bees#deer browsing plant#border planting#hairy leaves#pollinator plant#naturalized area#leathery leaves#Asian garden#flowers late spring#evergreen shrub#flowers early summer#understory planting#compact habit#understory shrub#problem for cats#problem for dogs#bee friendly#problem for horses#shrub borders#woodland garden#container plant#low hedge
 
Cultivars / Varieties:
  • 'Crete'
    Magenta buds, rose pink flowers fade to white
  • 'Van Zile'
'Crete', 'Van Zile'
Tags:
#showy flowers#deciduous#poisonous#houseplant#wildlife plant#pink flowers#slow growing#nectar plant#velvety#interiorscape#low maintenance#fall interest#year-round interest#hedges#specialized bees#deer browsing plant#border planting#hairy leaves#pollinator plant#naturalized area#leathery leaves#Asian garden#flowers late spring#evergreen shrub#flowers early summer#understory planting#compact habit#understory shrub#problem for cats#problem for dogs#bee friendly#problem for horses#shrub borders#woodland garden#container plant#low hedge
  • Attributes:
    Genus:
    Rhododendron
    Species:
    yakushimanum
    Family:
    Ericaceae
    Life Cycle:
    Woody
    Country Or Region Of Origin:
    Japan
    Wildlife Value:
    Members of the genus Rhododendron support the following specialized bee: Andrena (Andrena) cornelli. This plant tolerates damage by rabbits
    Dimensions:
    Height: 2 ft. 0 in. - 9 ft. 0 in.
    Width: 2 ft. 0 in. - 3 ft. 0 in.
  • Whole Plant Traits:
    Plant Type:
    Poisonous
    Shrub
    Woody Plant Leaf Characteristics:
    Broadleaf Evergreen
    Habit/Form:
    Dense
    Spreading
    Maintenance:
    Low
    Texture:
    Coarse
  • Cultural Conditions:
    Light:
    Dappled Sunlight (Shade through upper canopy all day)
    Full sun (6 or more hours of direct sunlight a day)
    Partial Shade (Direct sunlight only part of the day, 2-6 hours)
    Soil Texture:
    High Organic Matter
    Loam (Silt)
    Sand
    Soil pH:
    Acid (<6.0)
    Soil Drainage:
    Good Drainage
    Moist
    Available Space To Plant:
    12 inches-3 feet
    NC Region:
    Coastal
    Mountains
    Piedmont
    USDA Plant Hardiness Zone:
    5b, 6a, 6b, 7a, 7b, 8b, 8a
  • Fruit:
    Display/Harvest Time:
    Fall
    Summer
    Fruit Type:
    Capsule
    Fruit Description:
    Dry capsule apear in summer and matures in fall and have 5 valves
  • Flowers:
    Flower Color:
    Pink
    White
    Flower Inflorescence:
    Raceme
    Flower Value To Gardener:
    Showy
    Flower Bloom Time:
    Spring
    Summer
    Flower Shape:
    Bell
    Flower Petals:
    4-5 petals/rays
    Flower Size:
    1-3 inches
    Flower Description:
    Bright dark rose buds; opening to lighter pink to almost white bell-shaped flowers with 5 petals in late spring to early summer
  • Leaves:
    Woody Plant Leaf Characteristics:
    Broadleaf Evergreen
    Leaf Color:
    Brown/Copper
    Gray/Silver
    Green
    Leaf Feel:
    Glossy
    Leathery
    Velvety
    Leaf Type:
    Simple
    Leaf Arrangement:
    Alternate
    Leaf Shape:
    Lanceolate
    Oblanceolate
    Leaf Margin:
    Entire
    Hairs Present:
    Yes
    Leaf Length:
    3-6 inches
    Leaf Width:
    1-3 inches
    Leaf Description:
    Alternate, simple, glossy gray-green lanceolate to oblanceolate leaves curve downward; abundant brown hairs on underside of leaf; 3 to 3.5 in. long. New growth is covered in velvety white hairs.
  • Stem:
    Stem Is Aromatic:
    No
  • Landscape:
    Landscape Location:
    Container
    Houseplants
    Naturalized Area
    Woodland
    Landscape Theme:
    Asian Garden
    Pollinator Garden
    Design Feature:
    Border
    Hedge
    Attracts:
    Pollinators
    Specialized Bees
    Problems:
    Poisonous to Humans
    Problem for Cats
    Problem for Dogs
    Problem for Horses
  • Poisonous to Humans:
    Poison Severity:
    High
    Poison Symptoms:
    Salivation, watering of eyes and nose, abdominal pain, loss of energy, depression, nausea and vomiting, diarrhea, weakness, difficult breathing, progressive paralysis of arms and legs, coma.
    Poison Toxic Principle:
    Andromedotoxin
    Causes Contact Dermatitis:
    No
    Poison Part:
    Bark
    Flowers
    Fruits
    Leaves
    Roots
    Sap/Juice
    Seeds
    Stems