Bloomipedia
Low smartweed (Persicaria longiseta)
Photo: Jonathan Layman via iNaturalist · CC BY 4.0 · resized

Flower profile

Low smartweed

Persicaria longiseta

Introduced in the lower 48

Low smartweed is a wildflower that USDA PLANTS lists as introduced in the lower 48 states. It's on our flower lists for 22 states, and across the U.S. it's most often seen in bloom in June–October.

34states
22of our state lists
45,824U.S. sightings*

*iNaturalist research-grade observations, as of October 17, 2026.

On our lists for: Alabama, Arkansas, Connecticut, Delaware, Georgia, Illinois, Indiana, Iowa, Kentucky, Maryland, Massachusetts, Missouri, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, West Virginia

Quick look

Persicaria longiseta is a species of flowering plant in the knotweed family known by the common names Oriental lady's thumb, bristly lady's thumb, Asiatic smartweed, long-bristled smartweed, low smartweed, Asiatic waterpepper, bristled knotweed, bunchy knotweed, and tufted knotweed. It is native to Asia, and it is present in North America and Europe as an introduced species and often a weed.

  • It belongs to the Polygonaceae family. iNaturalist
  • USDA PLANTS describes it as an herb (forb) with a annual life cycle. USDA PLANTS
  • USDA PLANTS lists it as introduced in the lower 48 states and records it in 34 states. USDA PLANTS
  • In New York, most iNaturalist sightings of it in flower come in June–November. iNaturalist
  • In Pennsylvania, most iNaturalist sightings of it in flower come in June–October. iNaturalist
  • iNaturalist has 4,636 research-grade sightings of it in New York, ranking #45 among the 109 flowers on our New York list. iNaturalist
  • iNaturalist has 4,152 research-grade sightings of it in Pennsylvania, ranking #42 among the 111 flowers on our Pennsylvania list. iNaturalist
  • iNaturalist has 3,639 research-grade sightings of it in Virginia, ranking #44 among the 110 flowers on our Virginia list. iNaturalist

Low smartweed gift ideas

Handmade low smartweed gifts from independent makers.

When does it bloom?

Flowering records by month across the U.S. (iNaturalist research-grade observations marked “Flowering”) (2,588 records)
Bloom time in each of our 22 states
StateTypePeak bloomSightings*
New YorkIntroducedJune–November4,636
PennsylvaniaIntroducedJune–October4,152
VirginiaIntroducedJuly–October3,639
North CarolinaIntroducedJuly–October3,586
OhioIntroducedJune–October3,207
MarylandIntroducedMay–October2,957
New JerseyIntroducedJune–November2,863
MassachusettsIntroducedJune–October2,475
IllinoisIntroducedJune–October1,962
TennesseeIntroducedJuly–October1,906
IndianaIntroducedJuly–October1,725
MissouriIntroducedMay–October1,445
GeorgiaIntroducedMay–November1,418
KentuckyIntroducedMay–November989
AlabamaIntroducedMay–October986
ConnecticutIntroducedJune–October963
ArkansasIntroducedMay–October854
West VirginiaIntroducedJuly–October547
South CarolinaIntroducedfew records513
DelawareIntroducedfew records441
IowaIntroducedfew records389
Rhode Island–few records303

Conservation status

Federal (U.S. ESA)
Not listed No U.S. Endangered Species Act listing in the USFWS ECOS database. USFWS ECOS
NatureServe global
GNR Not yet ranked worldwide. NatureServe
New York
Not listed Not on New York protected native plants (6 NYCRR § 193.3). NatureServe: SNA, not applicable (usually because it isn't native there) in New York. 6 NYCRR § 193.3
Pennsylvania
Not listed Not on Pennsylvania classified native plants (17 Pa. Code Ch. 45, Subchapter B, as amended 2023). NatureServe: SNA, not applicable (usually because it isn't native there) in Pennsylvania. 17 Pa. Code Ch. 45
Virginia
Not listed Not on Virginia endangered and threatened plant and insect species (2VAC5-320-10). NatureServe: SNA, not applicable (usually because it isn't native there) in Virginia. 2VAC5-320-10
North Carolina
Not listed Not on North Carolina Protected Plant Species List (02 NCAC 48F .0301). NatureServe: SNA, not applicable (usually because it isn't native there) in North Carolina. 02 NCAC 48F .0301
Ohio
Not listed Not on Ohio endangered and threatened plants (Ohio Adm. Code 1501:18-1-03, eff. Dec. 26, 2024). NatureServe: SNA, not applicable (usually because it isn't native there) in Ohio. OAC 1501:18-1-03
Maryland
Not listed Not on Maryland threatened and endangered plants (COMAR 08.03.08.05, .06 and .08). NatureServe: SNA, not applicable (usually because it isn't native there) in Maryland. COMAR 08.03.08
New Jersey
Not listed Not on New Jersey Endangered Plant Species List (N.J.A.C. 7:5C-5.1). NatureServe: SNA, not applicable (usually because it isn't native there) in New Jersey. N.J.A.C. 7:5C-5.1
Massachusetts
Not listed Not on Massachusetts Endangered Species Act list (321 CMR 10.90). NatureServe: SNA, not applicable (usually because it isn't native there) in Massachusetts. MESA list
Illinois
Not listed Not on Illinois List of Endangered and Threatened Flora (17 Ill. Adm. Code 1050), per the Endangered Species Protection Board's 2025 checklist. NatureServe: SNA, not applicable (usually because it isn't native there) in Illinois. IL E&T checklist 2025
Tennessee
Not listed Not on Tennessee endangered plants (Tenn. Comp. R. & Regs. 0400-06-02-.04, Rare Plant Protection and Conservation Act). NatureServe: SNA, not applicable (usually because it isn't native there) in Tennessee. TN rule 0400-06-02-.04
Indiana
No list Indiana has no state law listing endangered or threatened plants (the DNR keeps a rare plant list, but it isn't regulatory), so we show NatureServe's Indiana ranks instead. NatureServe: SNA, not applicable (usually because it isn't native there) in Indiana.
Missouri
Not listed Not on Missouri Wildlife Code endangered species (3 CSR 10-4.111), plants. NatureServe: SNA, not applicable (usually because it isn't native there) in Missouri. 3 CSR 10-4.111
Georgia
Not listed Not on Georgia protected plants (Ga. Comp. R. & Regs. 391-4-10-.09; a 2026 update is proposed). NatureServe: SNA, not applicable (usually because it isn't native there) in Georgia. Ga. R. 391-4-10-.09
Kentucky
Not listed Not on Kentucky endangered and threatened plant lists (400 KAR 3:040, eff. 2026). NatureServe: SNA, not applicable (usually because it isn't native there) in Kentucky. 400 KAR 3:040
Alabama
No list Alabama has no state law listing endangered or threatened plants, so we show NatureServe's Alabama ranks instead. NatureServe: SNA, not applicable (usually because it isn't native there) in Alabama.
Connecticut
Not listed Not on Connecticut Endangered, Threatened and Special Concern Plants (RCSA 26-306; 2015 list). NatureServe: SNA, not applicable (usually because it isn't native there) in Connecticut. CT E/T/SC list
Arkansas
No list Arkansas has no state law listing endangered or threatened plants, so we show NatureServe's Arkansas ranks instead. NatureServe: SNA, not applicable (usually because it isn't native there) in Arkansas.
West Virginia
No list West Virginia has no state law listing endangered or threatened plants (only federally listed species are protected), so we show NatureServe's West Virginia ranks instead. NatureServe: SNA, not applicable (usually because it isn't native there) in West Virginia.
South Carolina
No list South Carolina has no state law listing endangered or threatened plants, so we show NatureServe's South Carolina ranks instead. NatureServe: SNA, not applicable (usually because it isn't native there) in South Carolina.
Delaware
Not listed Not on Rare and Uncommon Plants of Delaware (DNREC, 2024; informational, Delaware has no state plant-protection list). NatureServe: SNA, not applicable (usually because it isn't native there) in Delaware. DE rare plants 2024
Iowa
Not listed Not on Iowa endangered, threatened and special concern plants (Iowa Admin. Code r. 571-77.3). NatureServe: SNA, not applicable (usually because it isn't native there) in Iowa. IAC 571-77.3
Rhode Island
Not listed Not on Rhode Island Rare Plants 2016 (RI Natural History Survey, from the RI Wildlife Action Plan; informational, Rhode Island has no state plant-protection listing law). NatureServe has no Rhode Island rank for it. RI rare plants 2016
Rare elsewhere
No other U.S. state ranks it S1, S2, SH or SX.

Checked October 17, 2026. Rankings and lists can change, so follow the links for the latest.

Can you eat it?

For peopleNot well documented

None of the sources we checked (NC State Extension (no page for this plant), USDA PLANTS) say whether it's edible or poisonous for people.

For petsNot well documented

It isn't on the ASPCA plant list.

🌿 Never eat a wild plant unless you're certain of its ID; this isn't medical advice. Worried about a person? Call Poison Control at 1-800-222-1222. Worried about a pet? Call your vet.

Where does it grow?

USDA PLANTS records low smartweed in 34 states plus Washington, D.C.

recorded by USDA PLANTS on our state lists not recorded

See the full list of states

Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Nebraska, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Texas, Vermont, Virginia, West Virginia, Wisconsin; District of Columbia.

New York counties with USDA records: Albany, Bronx, Chemung, Delaware, Dutchess, Greene, Kings, Nassau, New York, Oneida, Onondaga, Orange, Putnam, Queens, Rensselaer, Richmond, Rockland, Saratoga, Schuyler, Suffolk, Tompkins, Ulster, Warren, Westchester.

Pennsylvania counties with USDA records: Adams, Allegheny, Armstrong, Beaver, Bedford, Berks, Blair, Bradford, Bucks, Butler, Centre, Chester, Clarion, Clinton, Cumberland, Dauphin, Delaware, Erie, Fayette, Franklin, Fulton, Indiana, Juniata, Lackawanna, Lancaster, Lehigh, Luzerne, Monroe, Montgomery, Northampton, Perry, Philadelphia, Pike, Venango, Warren, Washington, Wayne, Westmoreland, Wyoming, York.

Virginia counties with USDA records: Accomack, Albemarle, Amelia, Amherst, Appomattox, Arlington, Augusta, Bath, Bedford, Bland, Botetourt, Buckingham, Campbell, Caroline, Charlotte, Chesapeake , Chesterfield, Clarke, Craig, Culpeper, Cumberland, Dickenson, Essex, Fairfax, Fauquier, Fluvanna, Franklin, Frederick, Giles, Gloucester, Goochland, Grayson, Greene, Halifax, Hanover, Henrico, Henry, Isle of Wight, James City, King George, King William, Lee, Loudoun, Louisa, Madison, Mecklenburg, Middlesex, Montgomery, Nelson, Newport News , Northampton, Orange, Page, Patrick, Pittsylvania, Powhatan, Prince Edward, Prince George, Prince William, Pulaski, Rappahannock, Rockbridge, Rockingham, Russell, Scott, Shenandoah, Smyth, Spotsylvania, Stafford, Suffolk , Surry, Sussex, Tazewell, Warren, Westmoreland, Wise, York.

More New York flowers

Sources