marshpepper knotweed
Polygonum hydropiper · Polygonaceae
marshpepper knotweed (Polygonum hydropiper) is a annual herbaceous plant in the Polygonaceae family. It is introduced to North America rather than native. USDA records it as hardy in zone 12 and warmer, down to about 52°F.
At a glance
| Type | forb-herb USDA |
|---|---|
| Lifecycle | annual USDA |
| Native status | introduced USDA |
| Mature height | 1.6 ft USDA |
| Light | full-sun USDA |
| Water need | high USDA |
| Growth rate | rapid USDA |
| Soil pH | 5–7.5 USDA |
| Bloom | May–June USDA |
| Flower color | Red USDA |
| Hardiness zones | 12 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 needs full sun. USDA rates it as having needs consistently moist ground. Its drought tolerance is rated none — it needs reliable moisture. It is recorded on soils from pH 5 to 7.5 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 12.
Size and growth
At maturity it reaches about 1.6 ft, making it about knee height. It grows quickly.
Bloom period
USDA records a bloom period of May through June. Flowers are red.
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 summer.
What the site needs to provide
USDA records it across sites receiving 24 to 60 inches of annual precipitation. It needs at least 120 frost-free days to finish its season. It roots to at least 6 inches. Fertility requirement: medium.
Propagating it
Seed is the only propagation method USDA lists. Division and cuttings are not listed as options. USDA records no cold-stratification requirement, so seed should germinate without a chilling period. Its seed spreads at a moderate rate. It does not spread vegetatively, so it will stay where you put it.
Resilience and wildlife
Its fire tolerance is rated none. Its growth form is recorded as single crown.
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
Others in Polygonum
- water knotweed Polygonum amphibium
- meadow bistort Polygonum bistorta
- American bistort Polygonum bistortoides
- Davis' knotweed Polygonum davisiae
Similar role and hardiness
- bearded beggarticks Bidens aristosa
- crowned beggarticks Bidens coronata
- smooth beggartick Bidens laevis
- golden tickseed Coreopsis tinctoria
- annual rabbitsfoot grass Polypogon monspeliensis
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol POHY, 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, 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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