Polygonum praetermissum is a knotweed that is now usually listed as Persicaria praetermissa; the genus Persicaria was long equated with Polygonum.15 Its range extends from the Himalaya through South, East and South-East Asia to eastern and south-eastern Australia.15 The annual plant grows in marshes and along stream banks; scattered backward-pointing prickles sit on the angles of its decumbent to erect stems, and the lanceolate leaves have a sagittate base.3
It was first introduced as Polygonum sp. 'Ruby'.24 Under water it forms narrowly hastate leaves in reddish brown to orange-brown and grows in a straggly, oblique to horizontal manner.4 Medium to strong light and a good supply of CO₂ and nutrients are beneficial; it grows fairly quickly, and propagation from cuttings is easy.24
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