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Rhododendron maximum

Phonetic Spelling
rho-doh-DEN-dron MAKS-ih-mum
This plant has high severity poison characteristics.
See below
Description

Rosebay rhododendron is an evergreen shrub in the Ericaceae (blueberry) family that grows 10 to 20 feet tall. It is native to North America from Ontario and Nova Scotia south to Ohio, Alabama, and Georgia, with a concentration of plants in the southern Appalachian Mountains. The genus name derives from the Greek words rhodo, which means rose, and dendron, meaning tree.

This plant prefers moist, well-drained, richly organic, acidic soils in dappled shade and protection from afternoon sun, which can scorch the leaves. It will not tolerate dense clay, and the roots may rot if the soil does not drain well. Plant the root ball high in the soil to help with drainage. Its shallow, fibrous root system (do not cultivate around plants) will benefit greatly from a mulch of wood chips, bark, or pine needles to help retain moisture and stabilize soil temperatures. Avoid overwatering and over-fertilizing. Pruning, if desired, may be done after flowering.

Rosebay rhododendron’s habit is upright, loose, and multi-stemmed. The bark is thin, smooth, and light brown on young trees. As the tree ages, thin scales develop. This species blooms later than some, and the flowers attract bees, butterflies, hummingbirds, and other pollinators.

Rosebay rhododendron does well as an understory shrub planted in groups in woodland or naturalized areas, or as specimens in butterfly or pollinator gardens. As an evergreen it adds interest in a winter garden.

Fire Risk: This plant has a medium flammability rating. 

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.

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. 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:
  • 'Album'
  • 'Purpureum'
  • 'Red River'
  • 'Summer Glow'
  • 'Summer Solace'
  • var. album
  • var. purpureum
  • var. roseum
'Album', 'Purpureum', 'Red River', 'Summer Glow', 'Summer Solace', var. album, var. purpureum, var. roseum
Tags:
#hummingbirds#evergreen#poisonous#wildlife plant#native tree#nectar plant#native shrub#shade garden#cover plant#winter interest#fall interest#specialized bees#fire medium flammability#NC native#pollinator plant#food source fall#food source herbage#food source nectar#food source pollen#Coastal FAC#Piedmont Mountains FAC#butterfly friendly#nectar plant early summer#nectar plant mid-summer#nectar plant late summer#problem for cats#problem for dogs#bee friendly#problem for horses#Audubon#woodland garden
 
Cultivars / Varieties:
  • 'Album'
  • 'Purpureum'
  • 'Red River'
  • 'Summer Glow'
  • 'Summer Solace'
  • var. album
  • var. purpureum
  • var. roseum
'Album', 'Purpureum', 'Red River', 'Summer Glow', 'Summer Solace', var. album, var. purpureum, var. roseum
Tags:
#hummingbirds#evergreen#poisonous#wildlife plant#native tree#nectar plant#native shrub#shade garden#cover plant#winter interest#fall interest#specialized bees#fire medium flammability#NC native#pollinator plant#food source fall#food source herbage#food source nectar#food source pollen#Coastal FAC#Piedmont Mountains FAC#butterfly friendly#nectar plant early summer#nectar plant mid-summer#nectar plant late summer#problem for cats#problem for dogs#bee friendly#problem for horses#Audubon#woodland garden
  • Attributes:
    Genus:
    Rhododendron
    Species:
    maximum
    Family:
    Ericaceae
    Life Cycle:
    Woody
    Country Or Region Of Origin:
    North America
    Distribution:
    Ontario and Nova Scotia south to Ohio, Alabama, and Georgia
    Fire Risk Rating:
    medium flammability
    Wildlife Value:
    It proves winter and extreme weather coverage.  Hummingbirds, butterflies, and bees are attracted to its blooms for nectar.  Members of the genus Rhododendron support the following specialized bee: Andrena (Andrena) cornelli.
    Dimensions:
    Height: 5 ft. 0 in. - 15 ft. 0 in.
    Width: 5 ft. 0 in. - 12 ft. 0 in.
  • Whole Plant Traits:
    Plant Type:
    Native Plant
    Poisonous
    Shrub
    Tree
    Woody Plant Leaf Characteristics:
    Broadleaf Evergreen
    Habit/Form:
    Erect
    Open
    Maintenance:
    Medium
    Texture:
    Coarse
  • Cultural Conditions:
    Light:
    Deep shade (Less than 2 hours to no direct sunlight)
    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
    Occasionally Dry
    Available Space To Plant:
    6-feet-12 feet
    NC Region:
    Mountains
    Piedmont
    USDA Plant Hardiness Zone:
    3a, 3b, 4b, 4a, 5a, 5b, 6a, 6b, 7b, 7a
  • Fruit:
    Display/Harvest Time:
    Fall
    Fruit Type:
    Capsule
    Fruit Description:
    Oblong seed capsule which splits open when ripe to release numerous seeds. Displays from September to October.
  • Flowers:
    Flower Color:
    Green
    Orange
    Pink
    White
    Flower Inflorescence:
    Raceme
    Flower Value To Gardener:
    Showy
    Flower Bloom Time:
    Summer
    Flower Shape:
    Funnel
    Flower Size:
    1-3 inches
    Flower Description:
    Flowers (to 2” across) rose-purplish to pink to white, often with olive green to orange spots. Flowers bloom in umbel-like raceme inflorescences from June to August.
  • Leaves:
    Woody Plant Leaf Characteristics:
    Broadleaf Evergreen
    Leaf Color:
    Green
    Leaf Feel:
    Leathery
    Smooth
    Leaf Type:
    Simple
    Leaf Arrangement:
    Alternate
    Leaf Margin:
    Entire
    Hairs Present:
    Yes
    Leaf Length:
    > 6 inches
    Leaf Description:
    Large, alternate, simple dark green and leathery with a smooth margin and rust covered hairs on the undersides. They can range from 4 to 8 inches long.
  • Bark:
    Bark Color:
    Light Brown
    Surface/Attachment:
    Smooth
    Bark Description:
    The bark is thin, smooth and light brown on young trees. As the tree ages, thin scales develop.
  • Stem:
    Stem Is Aromatic:
    No
  • Landscape:
    Landscape Location:
    Houseplants
    Naturalized Area
    Woodland
    Landscape Theme:
    Butterfly Garden
    Pollinator Garden
    Winter Garden
    Design Feature:
    Small groups
    Specimen
    Attracts:
    Bees
    Butterflies
    Hummingbirds
    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
    Seeds
    Stems