What is Japanese knotweed?(Fallopia japonica)
- Japanese knotweed is an environmental weed.
- Japanese knotweed is a
declared weed in Tasmania under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of Japanese knotweed are prohibited in Tasmania.
How to identify Japanese knotweed
knotweed is a fast growing, hollow-stemmed and semi-woody perennial
plant that forms dense leafy thickets. Plants are commonly 2-3 metres
high and may reach 5 metres in height.
- Japanese knotweed stems
are stiff, hollow and bamboo-like, becoming tough, woody and speckled
with age. The stems arise at intervals from rhizomes or underground
stems. Leaves measure up to 12 cm long and 10 cm wide and have a pointed
- Japanese knotweed flowers from December to February.
Flowers are small and white and borne on slender branched spikes. Fruit
is a three-angled papery sheath that covers a single shiny black seed.
Most of the foliage dies back over autumn.
- Roots are coarse,
perennial rhizomes which are yellow when cut. They grow up to three
metres deep and spread many metres from the parent plant.
Image top right: Japanese knotweed leaves (Chris Moore)
Image above: Japanese knotweed infestation (Chris Moore)
Japanese knotweed in Tasmania
- Japanese knotweed occurs in northern Tasmania, mostly in garden situations (see map). Japanese knotweed has not been recorded in the north-west or in the south of Tasmania.
knotweed is a significant weed in riparian (river-side) areas,
disturbed coastal habitats, wetlands and roadsides, where it displaces
other vegetation by shading and root competition. Japanese knotweed dies
back over winter, leaving bare soils open to erosion.
rhizomes (underground stems) of Japanese knotweed can spread under
walls, pavements and patios and cause damage to roads and buildings.
What is the legal status of Japanese knotweed in your area?Detailed management and control guidelines for Japanese knotweed can be found in the
Japanese Knotweed Control Guide. Refer also to
Herbicides for Japanese Knotweed Control. For further information see
DPIPWE's Weed Links and Resources.
Japanese Knotweed Control Guide
Herbicides for Japanese Knotweed Control
Japanese Knotwood Statutory Management Plan
Weed Links and Resources
Other useful links
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