Index / Search / Polygonum amphibium
§1 Plant — species · Polygonaceae
Polygonum amphibium L.
vernacular water knotweed
§2Habit & range
Habit and range
- Growth habit
- Forb/herb
- Duration
- Perennial
- Group
- Dicot
- Family
- Polygonaceae Juss.
- Genus
- Polygonum
§2a
Native status, by region
- AK Alaska Native
- CAN Canada Native
- L48 Lower 48 States Native
- SPM St. Pierre & Miquelon Native
§3Cultivation specs · USDA
Recorded by the USDA Plant Materials Program.
§3a
Tolerances
- Drought
- None
- Shade
- High
- Moisture use
- High
- Fire
- Medium
- Salinity
- None
- Anaerobic
- High
- CaCO₃
- Medium
- Hedging
- None
§3b
Climate & soil
- Cold tolerance
- -23 °F minimum
- Frost-free days
- 110 min.
- Precipitation
- 14–60 in/yr
- pH range
- 4–7
- Root depth
- 6 in min.
- Fertility need
- Medium
- Soil texture
- medium, fine
§3c
Form & growth
- Growth form
- Rhizomatous
- Growth rate
- Moderate
- Lifespan
- Moderate
- Mature height
- 0.1 ft
- Foliage texture
- Medium
- Foliage colour
- Green
- Porosity (summer)
- Porous
- Porosity (winter)
- Porous
- Flower colour
- Yellow
- Fruit colour
- Brown
- Fire resistant
- Yes
- N fixation
- None
- Toxicity
- None
§3d
Reproduction
- Bloom period
- Late Spring
- Seed abundance
- Low
- Seed begins
- Summer
- Seed ends
- Fall
- Spread rate
- Moderate
- Stratify
- No
- Seeds / lb
- 125,000
- Propagation
- seed
§3e
Use & availability
- Commercial availability
- Routinely Available
- Nursery stock
- No
- Graze palatability
- Medium
- Palatable, human
- No
- Lumber
- No
- Christmas tree
- No
§4Montana distribution
Recorded in 24 of 56 Montana counties.
Native · 24 counties
- Beaverhead 30001
- Carter 30011
- Cascade 30013
- Fergus 30027
- Flathead 30029
- Gallatin 30031
- Glacier 30035
- Golden Valley 30037
- Hill 30041
- Lake 30047
- Lincoln 30053
- Madison 30057
- McCone 30055
- Missoula 30063
- Park 30067
- Phillips 30071
- Ravalli 30081
- Roosevelt 30085
- Sheridan 30091
- Silver Bow 30093
- Sweet Grass 30097
- Teton 30099
- Valley 30105
- Wheatland 30107
§5Sources & provenance
USDA PLANTS
Symbol, taxonomy, distribution, cultivation specs, native status. Public domain.
plants.usda.gov/POAM8 ↗GBIF Backbone
Canonical taxonomic identity, synonym resolution, cross-refs. CC0.
gbif.org/species/6391648 ↗Record version
Cached and built locally. Source version on this record:
usda-plants-mt-2026-05-25
fetched 2026-05-25T16:28:53Z