World Plants

Rhododendron ponticum (Common Rhododendron, Pontic Rhododendron)

Michael's Opinion

An outstanding plant but, has now invaded most of the woodlands of England with environmentalists mounting aggressive campaigns for its removal.

Botanical Information

Family	Ericaceae
Genus	Rhododendron
Species	ponticum
Category	Woody
Type	Shrub (evergreen)
References	Many cultivars can be easily found in its hardiness zone; however I believe that it will be hard to locate anyone selling Rhododendron ponticum, because it is such an invasive species.
Origin	Native to Southern Europe, Turkey, and the Caucasus region. Introduced into the British Isles in the second half of the eighteenth century.
Pronunciation

Details

USDA Hardiness Zone	4-8
USDA Hardiness Ref.
Canadian Hardiness Zone	2b-7b
Canada Hardiness Ref.
RHS Hardiness Ref.
Temperature (°C)	-34
Temperature (°F)	-30
Height	10 m
Spread	up to 100 m²
Growth	Fast
Flowering Period	June

Description and Growing Information

General Description	An invasive species in the United Kingdom. A spreading shrub with very dense foliage, growing up to 5 m in height.
ID Characteristic	Suckers often, forming an impenetrable wall of foliage. Thick glabrous leaves, large clusters of pink-purple flowers. Forms a 'canopy' of foliage at the top of the plant.
Shape	Low growing dome.
Landscape	Informal hedge. Will provide a beautiful display of pink flowers which are very appealing. It is not recommended for use unless it is kept in check by trapping it between a house wall and a concrete pathway.
Propagation	Seeds germinate easily without any special treatment to break dormancy, tissue culture, and cuttings taken preferably in late July-August for specific cultivars. Cuttings should be treated with alcohol for 5 seconds, placed in a well drained media and misted.
Cultivation	Enjoys conditions with lots of rainfall and well drained, acidic soil. Likes full sun to thin, partial shade. Prone to salt damage and winter dessication.
Pests	Suffers from vine weevils, white fly, scale insects, caterpillars, aphids and honey fungus.
Notable Specimens	In the United Kingdom there are single plants that spread to cover more than 100 m², and reach a height of over 10 m.
Habitat	Mild, wet, richly acidic soil regions, lightly wooded and open meadow areas at lower elevations.
Bark/Stem Description	Dark brown-grey, mild fissures can be found on older growth.
Flower/Leaf Bud Description	Buds secrete a sticky residue.
Leaf Description	Thick, glabrous, simple leaves in a lanceolate/elliptical shape, leathery texture, 6-18 cm long and 2-5 cm wide, growing in a whorled pattern. Dark green above, light green underneath.
Flower Description	Purple, sometimes pinkish, with green, yellow or orange markings, 3.5-5 cm wide and just as deep, 10 stamens with long filaments. Flowers are hermaphrodite and grow in corymb shaped clusters at the shoot meristems.
Fruit Description	The fruit is a dry capsule 1.5-2.5 cm in length, filled with many seeds.
Colour Description	Dark green glabrous foliage, purple or purple-pink flowers with green, yellow or orange spots. The bark is a brownish-grey.
Texture Description	Medium-coarse.

Photographs

Scanning electron microscope image of pollen grain.

Scanning electron microscope image of pollen grain.

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