Wildflower (forb) · Polygonaceae
Swamp smartweed
Polygonum hydropiperoides
Swamp smartweed is recorded as native to 41 states and territories in Kew’s World Checklist of Vascular Plants and USDA PLANTS, and recorded in 1,266 counties of those states by USDA PLANTS.
Key facts · USDA PLANTS
Swamp smartweed at a glance
- Native in
- 1,266 counties, across 41 states and territories
- Estimated cold hardiness
- Zone 10b PLANTS minimum temperature 32°F
- Mature height
- Not recorded PLANTS mature height
- Light and water
- Full sun (shade-intolerant) Medium water use
Estimated cold hardiness: zone 10b. PLANTS gives a minimum temperature of 32°F; zone 10b winters bottom out at 35°F, the coldest half-zone that stays within that limit.
Swamp smartweed is recorded as native to 41 states and territories in Kew’s World Checklist of Vascular Plants and USDA PLANTS, and recorded in 1,266 counties of those states by USDA PLANTS.
Counties where it is native
The 15 counties with the most ZIP codes among the 1,266 where it is listed.
Native counties by state
- Alabama 34 counties
- Arkansas 55 counties
- California 24 counties
- Connecticut statewide record
- Delaware 3 counties
- District of Columbia 1 county
- Florida 63 counties
- Georgia 34 counties
- Idaho 5 counties
- Illinois 90 counties
- Indiana 51 counties
- Iowa 5 counties
- Kansas 46 counties
- Kentucky 52 counties
- Louisiana 61 counties
- Maine 13 counties
- Massachusetts 14 counties
- Michigan 44 counties
- Minnesota 1 county
- Mississippi 51 counties
- Missouri 71 counties
- Nebraska 11 counties
- New Hampshire 7 counties
- New Jersey 21 counties
- New York 45 counties
- North Carolina 33 counties
- North Dakota 1 county
- Ohio 54 counties
- Oklahoma 28 counties
- Oregon 14 counties
- Pennsylvania 41 counties
- Rhode Island 4 counties
- South Carolina 26 counties
- South Dakota 2 counties
- Tennessee 57 counties
- Texas 86 counties
- Vermont 4 counties
- Virginia 56 counties
- Washington 11 counties
- West Virginia 30 counties
- Wisconsin 17 counties
Growing traits
Values from the PLANTS characteristics record. “Not recorded” means PLANTS has no value; nothing here is estimated except the zone.
Growth
- Growth habit
- Forb/herb
- Duration
- Perennial
- Mature height
- Not recorded
- Growth rate
- Slow
- Growth form
- Single Crown
- Shape
- Decumbent
- Lifespan
- Moderate
- Active growth period
- Summer
Light and water
- Shade tolerance
- Intolerant (full sun (shade-intolerant))
- Moisture use
- Medium water use
- Drought tolerance
- Low
- Tolerance of waterlogged soil
- High
- Precipitation range
- 12 to 50 in per year
Soil
- Soil textures
- Medium and fine
- pH range
- 4.5 to 8.8
- Lime (CaCO₃) tolerance
- High
- Salinity tolerance
- Low
- Fertility requirement
- Medium
- Minimum root depth
- 10 in
Climate
- Minimum temperature
- 32°F
- Estimated cold hardiness
- Zone 10b and warmer
- Minimum frost-free days
- 95
- Fire tolerance
- Medium
Flowers, leaves and fruit
- Flower color
- Green
- Showy flowers
- No
- Bloom period
- Indeterminate
- Foliage color
- Dark Green
- Showy in fall
- No
- Keeps leaves
- No
- Fruit color
- Green
Other
- Toxicity
- None
- Nitrogen fixation
- None
- Nursery availability
- Routinely Available
- Family
- Polygonaceae
- PLANTS symbol
- POHY2
Source & data date
- Source
- USDA NRCS PLANTS Database: county distribution records, native status and plant characteristics. CC0 (public domain dedication, per the data.gov catalog record).
- Kew’s World Checklist of Vascular Plants (WCVP): native or introduced status by state. CC BY 3.0.
- USGS US-RIIS (ver. 2.0): species listed as introduced are excluded. CC0.
- Citation
- USDA, NRCS. 2026. The PLANTS Database (https://plants.usda.gov, 11/04/2026). National Plant Data Team, Greensboro, NC USA.
- Govaerts R. (ed.) (2026). WCVP: World Checklist of Vascular Plants. Facilitated by the Royal Botanic Gardens, Kew. Data file dated 2026-06-04, http://sftp.kew.org/pub/data-repositories/WCVP/ (retrieved 2026-11-04). Paper: Govaerts R. et al. (2021) The World Checklist of Vascular Plants, a continuously updated resource for exploring global plant diversity. Scientific Data 8, 215.
- Data date
- Retrieved from PLANTS on November 4, 2026; WCVP data file dated June 4, 2026.
- Scope
- Polygonum hydropiperoides (PLANTS symbol POHY2).
- Method
- A species is listed when it is recorded as native to the state in Kew’s World Checklist of Vascular Plants and USDA PLANTS, and recorded in the county by USDA PLANTS. Species PLANTS labels both native and introduced are listed separately. Full method · All sources