Polygonum erectum is a North American species of annual plant species in the buckwheat family, with upright or ascending stems, called erect knotweed. It was once cultivated for food by Native Americans as part of the group of crops known as the Eastern Agricultural Complex. It is found primarily in the northeastern and north-central parts of the United States, but with scattered populations in other parts of the US and also in Canada.
L. 1753 not Roth 1783 nor Vell. 1827
Polygonum erectum grows 10–75 cm (4–29.5 in) tall with many to few, non-wiry branches. The leaves have distinct veins and entire edges or have jagged cut edges. The pedicels are shorter or equal the length of the calyx and typically longer than the ocreae. The closed flowers have a calyx that is typically 3 mm long, green in color and 5-lobed. Flowers in clusters of 1 to 5 in cymes that are produced in the axils of most leaves. The calyx segments are unequal with the outer lobes longer and not keeled and the inner ones narrowly keeled. The tepals are greenish, with yellowish tinting or sometimes with whitish tints. The seeds are produced in fruits called achenes that can be of two different types; one type is dark brown with a shiny surface and is broadly egg-shaped, typically about 2.5 mm (1–10 inch) long. The other achene type is dull brown, exsert and egg-shaped, and 3–3.5 mm (0.12–0.14 in) long. Late season fruiting is uncommon and if produced the achenes are 4 to 5 mm (0.16 to 0.20 in) long.
- Biota of North America Program 2014 county distribution map
- Gleason, A., Henry (1963). The new Britton and Brown illustrated flora of the northeastern United States and adjacent Canada. New York Botanical Garden by Hafner Pub. Co. pp. 72–84. LCCN 63016478.
- Flora of North America, Polygonum erectum Linnaeus, 1753. Erect knotweed, renouée dressée
- PLANTS Profile for Polygonum erectum (erect knotweed) | United States Department of Agriculture plants profile
- photo of herbarium specimen at Missouri Botanical Garden, collected in Missouri in 2000 (No image at link - January 26, 2018)