Invasive Alert! – Japanese Knotweed

August 25, 2014

Japanese Knotweed (Polygonum cuspidatum) was introduced from Asia as an ornamental, but has been found to be highly invasive. It thrives in wetlands and other marginal areas where it out-competes native vegetation. It is very difficult to control once established.

Japanese Knotweed is a semi-herbaceous perennial that can grow to 3 metres in height. It has reddish hollow stems resembling bamboo. Leathery leaves form at the joints and crown, 10 to 15 cm long. Greenish-white flowers in the summer

Japanese Knotweed prefers open habitats, and grows in a variety of soil types. It reproduces through creeping rhizomes, or root fragments. It is very easily spread through small pieces of root in contaminated soil

Dense stands can crowd out other vegetation. It is very persistent, and able to survive flooding. It poses a significant threat to hardscapes and waterways. Para Space plant health specialists can provide control options for this aggressive weed species.

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