Persicaria

Scientific name

Persicaria Mill.

Common names

smartweed, knotweed

Family

Polygonaceae

Similar genera

Potamogeton (rarely confused)

Native distribution

cosmopolitancosmopolitan:
(adj) essentially worldwide in distribution

Species cultivated

Persicaria amphibia (L.) Delarbe (Polygonum amphibium L.)

Persicaria hydropiperoides (Michx.) Small

Persicaria lapathifolia (L.) Delarbe (Polygonum lapathifolium L.)

Persicaria maculosa Gray (Polygonum persicaria L.)

Persicaria 'Sao Paulo' (species unknown)

Adventive distribution

The cultivated species listed are all introduced throughout the world.

Weed status

The cultivated species listed above are all considered serious environmental weeds.

Habit

emergent emergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
and terrestrialterrestrial:
(adj) growing on land as opposed to living in water
ascending stem plantstem plant:
(n) (a term used in the aquarium and pond plant trade) having an elongate stem (as opposed to a compact stem)
or small bush

Brief description

Annual or perennialperennial:
(adj) (of a plant) having a life cycle of more than two years
. Stem slender or robust, ascending to erect, rarely prostrateprostrate:
(adj) growing closely along the ground
. Leaves alternatealternate:
(adj) (of leaves) bearing one leaf per node; placed singly on the stem at different heights
, petiolatepetiolate:
(adj) relating to or in the form of a petiole; bearing petioles
or sessilesessile:
(adj) attached directly, without a stalk
; stipules united into a specialized sheath called an ocreaocrea:
(n) a sheath or tube formed at the base of the petiole by two united stipules, as in some members of the family Polygonaceae
; ocreaocrea:
(n) a sheath or tube formed at the base of the petiole by two united stipules, as in some members of the family Polygonaceae
silvery- or whitish-hyaline, with at least the upper part laceratelacerate:
(adj) torn; irregularly cut or slashed
; leaf bladeblade:
(n) (syn. lamina) the flat, expanded part of a leaf, frond, or petal (excluding, e.g., the petiole)
linear-lanceolate, ellipticelliptic:
(adj) in the form of an ellipse (oval)
to ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
; margins entireentire:
(adj) having a continuous margin that is not toothed or lobed
. Inflorescenceinflorescence:
(n) the arrangement of flowers on the floral axis
mostly terminalterminal:
(adj) at the apex
, spike-like. Flowers small; perianthperianth:
(n) collective term for the calyx and corolla of a flower; also used for floral whorl(s) in which the calyx and corolla cannot be resolved; any of the leaves or bracts surrounding the sex organs of bryophytes
of 4-5 tepals, subequal, free or fused at base, campanulatecampanulate:
(adj) bell-shaped
or urceolateurceolate:
(adj) urn-shaped
; sometimes heterostylousheterostylous:
(adj) (of flowers) having styles differing in length, shape or number in flowers among various plants of one species
. 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 66 species worldwide, with 10-20 aquatic species. The genus Persicaria was previously included in the genus Polygonum.