swamp azalea
Rhododendron viscosum · Ericaceae
swamp azalea (Rhododendron viscosum) is a perennial shrub in the Ericaceae family. It is native to North America. USDA records it as hardy in zone 5 and warmer, down to about -18°F.
At a glance
| Type | shrub USDA |
|---|---|
| Lifecycle | perennial USDA |
| Native status | native USDA |
| Mature height | 16 ft USDA |
| Light | shade USDA |
| Water need | high USDA |
| Growth rate | slow USDA |
| Soil pH | 4–7 USDA |
| Flower color | Red USDA |
| Hardiness zones | 5 and warmer USDA |
| Guild layer | shrub Derived |
| Nursery availability | Routinely Available USDA |
USDA quoted from the USDA PLANTS database · Derived computed by a fixed rule from those columns. No value on this page is estimated.
Growing conditions
It tolerates full shade. USDA rates it as having needs consistently moist ground. Its drought tolerance is rated medium. It handles periodically wet ground (USDA rates its anaerobic tolerance medium). It is recorded on soils from pH 4 to 7 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 5.
Size and growth
At maturity it reaches about 16 ft, making it a small tree or large shrub. It grows slowly.
Foliage, flower and season
Summer foliage is green, medium in texture. Its flowers are conspicuous. Its active growth period is spring. USDA rates its lifespan as moderate.
What the site needs to provide
USDA records it across sites receiving 35 to 55 inches of annual precipitation. It needs at least 160 frost-free days to finish its season. It roots to at least 14 inches. Fertility requirement: low — no feeding needed on ordinary garden soil.
Propagating it
Propagate it from seed, bare root and container stock. USDA records no cold-stratification requirement, so seed should germinate without a chilling period. Its seed spreads at a slow rate. It does not spread vegetatively, so it will stay where you put it.
Resilience and wildlife
Browsing animals rate it barely palatable — the sourced basis for calling it deer-resistant. Its fire tolerance is rated low. Its growth form is recorded as multiple stem.
Role in a guild
Shrub layer. In a layered planting this is woody mid-level structure between the understory and the ground. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Others in Rhododendron
- Cascade azalea Rhododendron albiflorum
- smooth azalea Rhododendron arborescens
- dwarf azalea Rhododendron atlanticum
- rhodora Rhododendron canadense
Similar role and hardiness
- red chokeberry Aronia arbutifolia
- sweet mock orange Philadelphus coronarius
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol RHVI2, or is computed from those values by a fixed rule. Nothing here is estimated or model-generated. Where USDA publishes no value, this page omits the claim rather than filling the gap.
- Quoted from USDA PLANTS: active growth period, browse palatability, cold stratification, Drought tolerance, fall conspicuous, fertility requirement, fire tolerance, Flower color, flower conspicuous, foliage color, foliage porosity winter, foliage texture, frost free days min, fruit conspicuous, growth form, Growth rate, Hardiness zones, Lifecycle, lifespan, Light, Mature height, Minimum temperature, Native status, Nitrogen fixation, Nursery availability, precipitation max in, precipitation min in, propagation, resprout ability, root depth in, seed spread rate, Soil pH, Soil pH (upper), Tolerance of wet soil, Toxicity, Type, vegetative spread rate, Water need.
- Derived by a fixed rule from those columns: Guild layer.
Read our full data sources and methodology.
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