Invasive weed that interferes with native plantlife new to Knox County

Local News

A dense patch of Japanese Chaff Flower along a wooded edge in Posey County.

VINCENNES, Ind. (WTWO/WAWV) — Japanese Chaff Flower, a perennial invasive weed in the Amaranth family, has invaded some private land near Decker Chapel in southern Knox County. Before now, the Japanese Chaff Flower (or JCF) was localized around the Ohio River Floodplain, with the closest known population in Gibson County.

JCF (Achyranthes japonica) can grow up to around 9 ft. tall and has opposite leaves as well as unique bottlebrush-like seedheads. Like other Amaranths (e.g. pigweeds, water hemp, etc.), JCF produces lots of seeds (anywhere from 100 to more than 1,000) per mature plant, and these seeds cling easily to fur, feathers and clothing. In addition, the seeds appear to spread along waterways, allowing JCF to quickly spread far and wide. Unlike other annual Amaranths, JCF will also spread outward via root growth, which would allow patches to become denser over time, if left untouched. This dense growth can lead to the inhibition of native and other desirable vegetation.

Ron Rathfon, extension forester with Purdue Extension, has been surveying and tracking JCF for years and says “Chaff flower forms extremely dense stands that exclude most other plants. Being shade tolerant, it grows in the shade of our forests and could interfere with establishment and growth of tree seedlings, impeding the regeneration of forests. Although not particularly difficult to kill using herbicides, it is extremely difficult to manage because of the abundant seed crop it produces annually. It is analogous to trying to contain spreading a wildfire.”

If you think you have JCF or want more information about it, contact Will Drews, Knox County Soil & Water Conservation District Natural Resource Specialist, at or (812) 882-8210, extension 3408.

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