American water-willow
Justicia americana · Acanthaceae
American water-willow (Justicia americana) is a perennial herbaceous plant in the Acanthaceae family. It is native to North America. USDA records it as hardy in zone 4 and warmer, down to about -28°F.
At a glance
| Type | forb-herb USDA |
|---|---|
| Lifecycle | perennial USDA |
| Native status | native USDA |
| Mature height | 2.5 ft USDA |
| Light | shade USDA |
| Water need | medium USDA |
| Growth rate | rapid USDA |
| Soil pH | 5.4–7.6 USDA |
| Bloom | May–June USDA |
| Flower color | White USDA |
| Hardiness zones | 4 and warmer USDA |
| Guild layer | herb-layer 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 moderate water needs. Its drought tolerance is rated low. It tolerates saturated, poorly drained ground well (USDA rates its anaerobic tolerance high). It is recorded on soils from pH 5.4 to 7.6 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 4.
Size and growth
At maturity it reaches about 2.5 ft, making it about knee height. It grows quickly.
Bloom period
USDA records a bloom period of May through June. Flowers are white.
A flowering date, not a pollinator rating.
Foliage, flower and season
Summer foliage is dark green, fine in texture. Its flowers are conspicuous. Its active growth period is spring.
What the site needs to provide
USDA records it across sites receiving 35 to 60 inches of annual precipitation. It needs at least 140 frost-free days to finish its season. It roots to at least 10 inches. Fertility requirement: low — no feeding needed on ordinary garden soil.
Propagating it
Bare root is the only propagation method USDA lists. Its seed spreads at a moderate rate. It spreads vegetatively at a rapid rate.
Resilience and wildlife
Browsing animals find it moderately palatable, so expect deer and rabbits to take an interest. Its fire tolerance is rated low. Its growth form is recorded as rhizomatous.
Role in a guild
Herb layer. In a layered planting this is the herbaceous middle — perennials and grasses that fill the space between ground cover and shrubs. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Similar role and hardiness
- Columbian monkshood Aconitum columbianum
- Colorado blue columbine Aquilegia coerulea
- mountain brome Bromus marginatus
- eastern woodland sedge Carex blanda
- scarlet Indian paintbrush Castilleja coccinea
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol JUAM, 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, Bloom, Bloom end, browse palatability, cold stratification, Drought tolerance, fall conspicuous, fertility requirement, fire tolerance, Flower color, flower conspicuous, foliage color, foliage texture, frost free days min, fruit conspicuous, growth form, Growth rate, Hardiness zones, Lifecycle, 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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