Scientific Name: Polygonum pensylvanicum
Synonyms: Persicaria bicornis, P. longistyla, P. mississippiensis, P. pensylvanica, Polygonum bicorne, P. longistylum, P. mexicanum, P. mississippiense
Common Names: Pennsylvania Smartweed, Pennsylvania Knotweed, Pinkweed, Pink Knotweed, Pinweed
Growth Habit: Herb/Forb
Arizona Native Status: Native
Habitat: Riparian. This water-loving plant grows in and along flowing streams and in other wetland areas with moist soil in the deserts and uplands.
Flower Color: Medium pink to very pale pink
Flowering Season: Spring, Summer, Fall
Height: To 3 feet (91 cm) tall or more
Description: The small flowers are densely clustered in up to 2 inch (5 cm) long, terminal flower spikes. The leaves are green, alternate, lance-shaped, and up to 6 inches (15 cm) long. The stems are jointed with a distinctive smooth-edged sheath covering each joint.
The similar Curlytop Knotweed (Polygonum lapathifolium) has whiter, longer, drooping, curved inflorescences, while Spotted Ladysthumb (Polygonum persicaria) and Swamp Smartweed (Polygonum hydropiperoides) have fringed stem sheaths.
Kingdom: Plantae – Plants
Subkingdom: Tracheobionta – Vascular plants
Superdivision: Spermatophyta – Seed plants
Division: Magnoliophyta – Flowering plants
Class: Magnoliopsida – Dicotyledons
Family: Polygonaceae – Buckwheat family
Genus: Polygonum L. – knotweed
Species: Polygonum pensylvanicum L. – Pennsylvania smartweed
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