About
Rhododendron viscosum, the swamp azalea, is a bushy deciduous shrub to 2.5 m with dark leaves that are glaucous beneath. Very fragrant, narrowly funnel-shaped, white flowers flushed deep pink on the tube open in early to mid summer. An elegant and sweetly scented azalea for a moist, acid woodland or bog garden.
About the genus
Rhododendron, the rhododendrons and azaleas, are a vast genus of evergreen and deciduous shrubs and trees producing simple leaves � sometimes with a dense, colourful indumentum beneath � and funnel-shaped, bell-shaped or tubular flowers in a wide range of colours in spring and early summer. They thrive in moist, acid, humus-rich, well-drained soil in dappled shade.
Growing conditions
SunlightFull sun, Partial shade
Soil typeClay, Loam, Sand
Soil pHAcid
Soil moistureMoist but well-drained
AspectSouth-facing, East-facing, West-facing
ExposureSheltered
UK hardinessH6
Plant details
Plant typeShrubs
HabitBushy
FoliageDeciduous
Height1.5-2.5 metres
Spread1.5-2.5 metres
Time to full height10-20 years
Suggested usesCity and courtyard gardens, Cottage and informal garden
Native toEastern N America
FragranceFlower
ToxicityHarmful if eaten. Wear gloves and other protective equipment when handling. Pets (dogs, cats, rabbits, tortoises) Harmful if eaten - for further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants
Care notes
CultivationGrow in moist but well-drained, leafy, humus-rich acid soil in part shade with shelter; sun tolerant if soil remains reliably moist; see rhododendron cultivation
PruningPruning group 1
PropagationPropagate by seed when ripe, or semi-ripe cuttings in late summer, layering in autumn or grafting in late summer or late winter
Pest resistanceMay be susceptible to vine weevil, rhododendron and azalea whitefly, rhododendron leafhopper, pieris lacebug, scale insects, caterpillars and aphids
Disease resistanceMay be susceptible to various Rhododendron diseases including powdery mildews, rhododendron petal blight, rhododendron bud blast, silver leaf and honey fungus