Asiatic Knotweed, Giant Knotweed

Also known as:
Polygonum Japonicum, P. Sachalinensis, Reynoutria Japonica, R Sachalinensis

General description

Upright shrublike herbaceous perennials rapidly grow to 3 m in height. Dioecious. Red-purple shoots appear early in spring, as the canes grow the leaves unfurl and plant turns green. Mature canes hollow with purple flecks. Leaves long triangular-oval (15 x 10 cm), pointed at the tip, with flattened leaf base. Flowers white creamy white (Dec-Mar).

Shrubland, riparian areas.

Vegetative growth from rhizomes

Once established, forms dense stands, shade and crowd out all other vegetation, displacing native flora and fauna.

Site management

WARNING! Fragments as small as 0.7 grams can form new plants, therefore be extremely careful with any equipment used on site.

Recommended approaches

1. Report it immediately to the Auckland Council Biosecurity team, who will arrange for its control at their expense.
2. Dig out small patches and dispose.
3. Stump swab (250ml glyphosate/1L or Vigilant gel or 5g metsulfuron/L or 200ml triclopyr/L)
4. Spray (5g metsulfuron + 200ml glyphosate + 10ml penetrant/10L or Tordon BK 100ml + 20ml penetrant/10L).

Caution: when using any herbicide or pesticide PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.

RPMS status

Total Control - Whole Region
National Pest Plant Accord species - nationwide
Asiatic knotweed, giant knotweed - Main species image