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Engineering

Japanese Knotweed (Report an Infestation)

Japanese Knotweed is a serious concern on stormwater land because it quickly forms dense stands and is capable of damaging infrastructure, displacing native vegetation, causing erosion, and disrupting riparian areas.
Due to its vigorous and nigh indestructible root system, Japanese Knotweed requires careful management to completely extinguish a population.

There have been numerous reports of knotweed being repeatedly mowed for over a decade, only to sprout right back up again. Another challenge to face is the ability of this invasive plant to resprout from cut fragments. Given contact with the soil, segments as small as half an inch have the ability to send down roots and grow.

Japanese Knotweed leaves grow alternately up the stem, are spade-shaped with a pointed tip, and have smooth edges. This invasive species flowers in late summer through fall and forms yellowish-white, tuft-like flowers at the base of the leaves.
Japanese Knotweed leaves grow alternately up the stem, are spade-shaped with a pointed tip, and have smooth edges. This invasive species flowers in late summer through fall and forms yellowish-white, tuft-like flowers at the base of the leaves.
The bamboo-like stalks are hollow and form segments separated by a reddish-brown band. This plant has no problem growing through concrete foundation and discarded scrap metal as it is doing here.
Caption: The bamboo-like stalks are hollow and form segments separated by a reddish-brown band. This plant has no problem growing through concrete foundation and discarded scrap metal as it is doing here.

Report an Infestation

We are doing everything we can to find and eradicate this species and need all the eyes we can get! If you think you have seen Japanese Knotweed on Engineering land, please take photos and send them to Vegetation Coordinator Madeline Dumas at mdumas2@cityofmadison.com for identification.

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