Persicaria

Scientific name

Persicaria Mill.

Common names

smartweed, knotweed

Family

Polygonaceae

Could be confused with

Alternanthera, Hygrophila, Murdannia

Native distribution

cosmopolitan

Species commonly cultivated

Persicaria amphibia (L.) Gray (Polygonum amphibium L.) (Africa, Asia, Europe, North America)

Persicaria hydropiper (L.) Spach (Polygonum hydropiper L.) (Africa, Asia, Australia, Europe)

Persicaria lapathifolia (L.) Gray (Polygonum lapathifolium L.) (Africa, Asia, Europe)

Persicaria maculosa Gray (Polygonum persicaria L.) (throughout temperate regions)

Adventive distribution

The cultivated species listed above are all introduced throughout the world and are considered serious environmental weeds.

Weed status

The cultivated species listed above are all introduced throughout the world and are considered serious environmental weeds.

Habit

emergent and terrestrial stem plant or bush

Brief description

Annual or perennial. Stem slender or robust, ascending to erect, rarely prostrate. Leaves alternate, petiolate or sessile; stipules united into a specialized sheath called an ocrea; ocrea silvery- or whitish-hyaline, with at least the upper part lacerate; leaf blade linear-lanceolate, elliptic to ovate; margins entire. Inflorescence mostly terminal, spike-like. Flowers small; perianth of 4-5 tepals, subequal, free or fused at base, campanulate or urceolate; sometimes heterostylous. Dispersal of nuts by animals or water.

Natural habitat

frequently in moist or inundated habitats; many can survive extended periods of inundation

Additional comments

Persicaria contains ca. 100 species worldwide, with 10-20 aquatic species. The genus Persicaria was previously included in the genus Polygonum.