Persicaria longiseta

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, Asiatic waterpepper, bristled knotweed, bunchy knotweed, and tufted knotweed. It is native to Asia (China, India, Russia, Japan, Malaysia, etc.),[2] and it is present in North America and Europe as an introduced species and often a weed.[3][4]

Persicaria longiseta
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Order:	Caryophyllales
Family:	Polygonaceae
Genus:	Persicaria
Species:	P. longiseta
Binomial name
Persicaria longiseta (Bruijn) Kitagawa 1937
Synonyms[1]
Polygonum cespitosum var. longisetum (Bruijn) C.F.Reed 1987 Polygonum longisetum Bruijn 1854 Polygonum caespitosum var. longisetum (Bruijn) Danser Polygonum cespitosum var. longisetum (Bruijn) Steward

Persicaria longiseta is an annual herb with stems 30 to 80 centimeters (12–32 inches) long,[5] sometimes reaching one meter (40 inches).[3] The hairless, branching stems may root at lower nodes that come in contact with the substrate. The leaves are lance-shaped and up to 8 centimeters (3.2 inches) long by 3 cm (1.2 inches) wide. They have bristly ochrea. The inflorescence is an elongate cluster up to 8 centimeters (3.2 inches) long and contains many pink flowers. The fruit is a small, smooth achene.[5]

In its native region this plant is a common weed of rice paddies. It was introduced to North America near Philadelphia around 1910 and probably spread via the railroads. It is present in much of the eastern United States and much of Canada.[6] It grows in moist habitat types such as wetlands, as well as dry and upland habitat. It can be found in meadows, marshes, mudflats, riverbanks, floodplains, levees, and lowland and upland forests. It is invasive in some areas.[3]

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