Polygonum pensylvanicum – Pennsylvania Smartweed

Polygonum pensylvanicum - Pennsylvania Smartweed, Pennsylvania Knotweed, Pinkweed, Pink Knotweed, Pinweed (flowers and a green bee)

Polygonum pensylvanicum - Pennsylvania Smartweed, Pennsylvania Knotweed, Pinkweed, Pink Knotweed, Pinweed

Plant Name

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

Plant Characteristics

Duration: Annual

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.

Classification

Kingdom: Plantae – Plants
Subkingdom: Tracheobionta – Vascular plants
Superdivision: Spermatophyta – Seed plants
Division: Magnoliophyta – Flowering plants
Class: Magnoliopsida – Dicotyledons
Subclass: Caryophyllidae
Order: Polygonales
Family: Polygonaceae – Buckwheat family
Genus: Polygonum L. – knotweed
Species: Polygonum pensylvanicum L. – Pennsylvania smartweed

More About This Plant

Arizona County Distribution Map