alligatorweed
Alternanthera philoxeroides · Amaranthaceae
alligatorweed (Alternanthera philoxeroides) is a perennial herbaceous plant in the Amaranthaceae family. It is introduced to North America rather than native. USDA records it as hardy in zone 6 and warmer, down to about -3°F.
⚠ Invasive or noxious status. USDA lists this plant with an invasive or noxious weed status somewhere in its range. Check your state's noxious weed list before planting it — in some states it is illegal to sell or plant.
Both flags are quoted from USDA PLANTS, not inferred.
At a glance
| Type | forb-herb USDA |
|---|---|
| Lifecycle | perennial USDA |
| Native status | introduced USDA |
| Mature height | 0.2 ft USDA |
| Light | part-shade USDA |
| Water need | high USDA |
| Growth rate | rapid USDA |
| Soil pH | 4.8–8.8 USDA |
| Bloom | March–April USDA |
| Flower color | White USDA |
| Hardiness zones | 6 and warmer USDA |
| Guild layer | ground-cover Derived |
| Nursery availability | No Known Source 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 grows in partial shade. USDA rates it as having needs consistently moist ground. 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 4.8 to 8.8 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 6.
Size and growth
At maturity it reaches about 0.2 ft, making it a low, mat-forming plant. It grows quickly.
Bloom period
USDA records a bloom period of March through April. Flowers are white.
A flowering date, not a pollinator rating.
Foliage, flower and season
Summer foliage is green, medium in texture. Its flowers are not conspicuous — a plant for form and foliage. Its active growth period is spring. USDA rates its lifespan as short, so plan on replacing or resowing it rather than treating it as permanent structure.
What the site needs to provide
USDA records it across sites receiving 40 to 60 inches of annual precipitation. It needs at least 200 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
Sprigs is the only propagation method USDA lists. It spreads vegetatively at a rapid rate.
Resilience and wildlife
Its fire tolerance is rated none. Its growth form is recorded as stoloniferous.
Role in a guild
Ground cover. In a layered planting this is the lowest layer — it shades soil, holds moisture, and suppresses weeds. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Similar role and hardiness
- thicket sedge Carex abscondita
- Egyptian clover Trifolium alexandrinum
- Korean lawngrass Zoysia japonica
- Manila grass Zoysia matrella
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol ALPH, 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, 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, Invasive status, 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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