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Korean Rhododendron Rhododendron mucronulatum

Phonetic Spelling
rho-doh-DEN-dron myoo-kron-yoo-LAY-tum
This plant has high severity poison characteristics.
See below
Description

Korean rhododendron is a woody, deciduous shrub in the Ericaceae (blueberry) family.  Its form is twisting, multistemmed and open and it has spectacular, showy, pink flowers that appear in late winter to early spring before its diamond-shaped leaves appear. Native to northeastern North America, it grows at a relatively slow rate to 4 to 8 feet tall and wide. The genus name derives from the Greek words rhodo, which means rose, and dendron, meaning tree.

This plant prefers moist, well-drained, acidic soils in dappled shade and protection from afternoon sun, which can scorch the leaves. Korean rhododendron is extremely cold hardy.  It does not tolerate dense clay, so if you have clay soil, amend with organic material. Plant the root ball high in the soil to help with drainage issues. Avoid overwatering and over-fertilizing. Pruning, if desired, may be done after flowering.  Mulch each year to keep the roots cool.

Korean rhododendron can be used as a cultivated, woody shrub in a mass planted in a woodland or natural area or as a specimen that will attract hummingbirds and bees to a pollinator garden.  It works well in a shrub border or as an accent plant and is attractive when planted near other early spring bloomers like daffodils and crocus.  

Insects, Diseases, and Other Plant Problems:  Insect problems include aphids, borers, lacebugs, 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. Early flowering makes it susceptible to spring freezes.

While Rhododendrons 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. 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:
  • 'Cornell Pink'
    Rich pink flowers
  • 'Mahogany Red'
    Deep pink flowers
'Cornell Pink', 'Mahogany Red'
Tags:
#showy flowers#deciduous#poisonous#specimen#pink flowers#slow growing#fragrant leaves#deciduous shrub#nectar plant#winter interest#fall interest#accent plant#specialized bees#frost tolerant#pollinator plant#flowers early spring#fall color yellow#nectar plant early spring#problem for cats#flowers late winter#problem for dogs#bee friendly#problem for horses#fall color orange-red#woodland garden#nectar plant late winter#wildlife friendly
 
Cultivars / Varieties:
  • 'Cornell Pink'
    Rich pink flowers
  • 'Mahogany Red'
    Deep pink flowers
'Cornell Pink', 'Mahogany Red'
Tags:
#showy flowers#deciduous#poisonous#specimen#pink flowers#slow growing#fragrant leaves#deciduous shrub#nectar plant#winter interest#fall interest#accent plant#specialized bees#frost tolerant#pollinator plant#flowers early spring#fall color yellow#nectar plant early spring#problem for cats#flowers late winter#problem for dogs#bee friendly#problem for horses#fall color orange-red#woodland garden#nectar plant late winter#wildlife friendly
  • Attributes:
    Genus:
    Rhododendron
    Species:
    mucronulatum
    Family:
    Ericaceae
    Life Cycle:
    Woody
    Country Or Region Of Origin:
    Northeastern North America
    Wildlife Value:
    Members of the genus Rhododendron support the following specialized bee: Andrena (Andrena) cornelli.
    Dimensions:
    Height: 4 ft. 0 in. - 8 ft. 0 in.
    Width: 4 ft. 0 in. - 8 ft. 0 in.
  • Whole Plant Traits:
    Plant Type:
    Poisonous
    Shrub
    Woody Plant Leaf Characteristics:
    Deciduous
    Habit/Form:
    Multi-stemmed
    Open
    Spreading
    Growth Rate:
    Slow
    Maintenance:
    Low
    Medium
    Texture:
    Fine
  • Cultural Conditions:
    Light:
    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:
    3 feet-6 feet
    6-feet-12 feet
    NC Region:
    Coastal
    Mountains
    Piedmont
    USDA Plant Hardiness Zone:
    4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b
  • Flowers:
    Flower Color:
    Pink
    Purple/Lavender
    Flower Inflorescence:
    Raceme
    Flower Value To Gardener:
    Showy
    Flower Bloom Time:
    Spring
    Winter
    Flower Shape:
    Funnel
    Flower Petals:
    4-5 petals/rays
    Flower Size:
    1-3 inches
    Flower Description:
    Bright rosy pink to pinkish purple funnel shaped flowers in clusters of 2 to 3 at the end of the branches. Flowers are up to 2 inches in spring before leaves emerge
  • Leaves:
    Woody Plant Leaf Characteristics:
    Deciduous
    Leaf Color:
    Gold/Yellow
    Green
    Leaf Value To Gardener:
    Fragrant
    Deciduous Leaf Fall Color:
    Brown/Copper
    Gold/Yellow
    Red/Burgundy
    Leaf Type:
    Simple
    Leaf Arrangement:
    Alternate
    Leaf Shape:
    Elliptical
    Lanceolate
    Leaf Margin:
    Entire
    Hairs Present:
    No
    Leaf Description:
    Alternate, simple, medium green narrow ellipitc to lanceolate leaves; aromatic when crushed; yellow, bronzy crimson red fall color
  • Stem:
    Stem Is Aromatic:
    No
  • Landscape:
    Landscape Location:
    Naturalized Area
    Woodland
    Landscape Theme:
    Pollinator Garden
    Winter Garden
    Design Feature:
    Accent
    Border
    Mass Planting
    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, cardiac failure, difficult breathing, progressive paralysis of arms and legs, coma.
    Poison Toxic Principle:
    Andromedotoxin, Grayantoxin
    Causes Contact Dermatitis:
    No
    Poison Part:
    Bark
    Flowers
    Fruits
    Leaves
    Roots
    Sap/Juice
    Seeds
    Stems