Skip to main content

Polygonum pensylvanicum - Pennsylvania smartweed

Scientific Family
Polygonaceae
Synonyms
Persicaria pensylvanica, Persicaria bicornis, Persicaria longistyla, Polygonum mexicanum
Other common names
pinkweed
Plant type
Forbs and Subshrubs
Origin
Native
Lifecycle
Annual
Height
1 to 4 feet
Riparian
Yes

This plant is more or less erect, branching occasionally and often bending toward the light in partially shaded locations.

Leaves have few or no hairs, upper stems and flower stems with usually red glands; stipules at base of the leaves cylindric without hairs; calyx (sepals) bright pink; inflorescences erect, in leaf axils and terminal, flower bracts reduced to sheaths.

Habitat

Moist, disturbed places, ditches, riverbanks, cultivated fields, shorelines of ponds and reservoirs.

Plant Community
Disturbed Areas
Riparian
Low elevation
2500
High elevation
7000

Flower Characteristics

Dense, erect, spike-like clusters of small, bright pink flowers are borne on sticky-haired stalks.

Flower color
Pink
Flower shape
Irregular
Tubular
No
First bloom month
May
Last bloom month
December
Flower clusters
Elongated

Leaf and Stem Characteristics

Leaves have membranous sheaths at the bases of the leaf stalks that surround the stems. Smooth round stems are light green to red and relatively stout; they have a tendency to zigzag between the alternate leaves.

Leaf type
Simple
Leaf color
Green
Leaf shape
Narrow
Leaf margin
Smooth
Leaf attachment
Alternate
Leaves clasp
No
Leaf hairs
Leaves & stems
Spines
No

Fruit and Seed Characteristics

Fruits are round in outline, generally nearly flat on 1 side, indented on other, dark brown and shiny.

Fruit type
Achene
Fruit color
Brown