Fallopia sachalinensis
NPPA pest plant
Environmental Weed (2024)
Common names
giant knotweed
Synonyms
Reynoutria sachalinensis (F.Schmidt) Nakai
Family
Polygonaceae
Flora category
Vascular – Exotic
Structural class
Herbs - Dicotyledons other than Composites
Conservation status
Not applicable
Habitat
Terrestrial.
Detailed description
Giant rhizomatous herb forming large thickets; stems glabrous, green, 2~4m high, approx. 2cm diam., woody at base. Petiole 2~6cm long, often reddish, channelled above, with 3 pits at base on dorsal side, except in some infl. leaves. Lamina 10~30 x 5~22cm, broad- to oblong-ovate, glaucescent below, entire to undulate, usu. glabrous when mature, or sometimes puberulent towards base of veins on upper side, with > 14 pairs of lateral veins; base shallow- to deep-cordate; sinus wide; apex acute to cuspidate. Ochreae to 6cm long, glabrous, soon deciduous. Panicle branches solitary or fascicled, at least the lower branches
Flowering
November, December, January, February, March, April
Flower colours
Green, White
Life cycle
Perennial.
Year naturalised
1935
Origin
E Asia, N Japan
Reason for introduction
Ornamental
National Pest Plant Accord species
This plant is listed in the 2020 National Pest Plant Accord. The National Pest Plant Accord (NPPA) is an agreement to prevent the sale and/or distribution of specified pest plants where either formal or casual horticultural trade is the most significant way of spreading the plant in New Zealand. For up to date information and an electronic copy of the 2020 Pest Plant Accord manual (including plant information and images) visit the MPI website.
Environmental Weed (2024)
This plant is named in a list of 386 environmental weeds in New Zealand 2024 prepared by DOC. 759 candidate species were considered for inclusion on this new comprehensive list of environmental weeds in New Zealand. The species considered were drawn from published lists of weed species, lists of plants that must be reported or managed by law if observed, existing national and regional programmes and agreements for pest management, and species already managed by the Department of Conservation (DOC). Candidate species were then assessed to see if they were fully naturalised and whether they have more than minor impacts in natural ecosystems. Read the full report here.