Celestine Duncan, TechLine editor. This article is adapted in part from Ecology and Control of Japanese Chaff Flower Fact Sheet. LM Schwartz, KM Smith, C. Evans, KL Gage, DJ Gibson, and BG Young. 2015. (Photos by Chris Evans, Univ. Ill, Bugwood.org).
Japanese chaff flower (Achyranthes japonica) is a highly invasive, non-native, perennial plant in the Amaranth family. The plant is native to the eastern and south-eastern regions of Asia and was first reported in 1981 along the Tug Fork River in Kentucky. The plant quickly spread down the Ohio River and currently infests nine states and over 50 counties (Figure 1). Distribution is likely underestimated due to lack of public awareness about the weed.
Japanese chaff flower is well adapted to a variety of ecological sites. The plant prefers moist, partially shaded forest bottom lands, but also infests upland forests, riverbanks, agricultural field margins, and roadsides. Although chaff flower is associated with waterways, it does not tolerate prolonged periods of inundation. The plant is best adapted to sites with partial sun and moist soils, but also grows in heavily shaded and dry areas.
Japanese chaff flower is highly competitive, forming tall, dense monocultures that shade out and displace many native and desirable species. The plant has high seed production (~2000 seeds/plant) with an average of 94 percent germination under desirable conditions. Each plant can produce more than 80 stems in three square feet, with an average of about 16,000 seeds per plant. Seedlings germinate throughout the summer, and about 60 percent of seedlings can produce seed the first year.
Japanese chaff flower begins growth in late spring. Plants can grow up to nine feet tall with lower stems reddish in color. Leaves are opposite and simple. Flowers are an erect spike at the ends of stems and occur from late summer through early fall (Figure 2). Seeds mature in mid- to late-fall and have two stiff bracts that aid in dispersal. Plants spread easily from contact with water, humans, wildlife and equipment. Dead plants remain erect into winter, which facilitates seed dispersal.
Japanese chaff flower spreads easily by mowing, agricultural and road maintenance equipment, recreationists, wildlife, and livestock. Mowing infested areas along roadsides, ditch banks, and field edges before chaff flower seed mature will reduce seed spread. Vehicles, pets, and clothing should be cleaned after recreating in areas infested with chaff flower, especially during seed dispersal (from early August through fall).
Southern Illinois University field and greenhouse studies showed several different herbicides will effectively control Japanese chaff flower (Table 1). Vastlan® specialty herbicide applied at 1 to 1.5 quarts per acre, or Milestone® specialty herbicide at 4 to 7 fluid ounces of product per acre, will provide good to excellent control when applied prior to seed set. Vastlan and Milestone are selective herbicides that will control chaff flower and allow grasses to continue to grow. Vastlan can be applied to a variety of sites, including areas in and around standing water, such as marshes, wetlands, and the banks of ponds and lakes. Do not apply Vastlan or Milestone over the top of desirable woody trees or shrubs as injury may occur. Japanese chaff flower often grows in forested areas. Information on the relative tolerance of various tree species to Milestone® specialty herbicide is available at bit.ly/NativeForbShrubTolerance.
Rodeo® and Accord® XRTII herbicides applied at 1 to 1.5 quarts per acre will provide good control of Japanese chaff flower. These are non-selective herbicides, which can kill or damage most plants coming into contact with the spray solution. A non-ionic surfactant approved for use on aquatic sites should be added to Rodeo. Herbicides should be applied prior to seed set.
Physical Control and Prescribed Fire
Digging or pulling chaff flower seedlings that have not developed a perennial root system (four nodes or less on the above-ground stem) will effectively control the plant. Pulling larger chaff flower plants can cause increased branching and seed production if the root system is broken during removal. Mowing in mid-summer prior to flowering (late July to early August) can reduce chaff flower seed production; however, follow-up treatment with herbicides will be necessary to control the plants.
Prescribed fire in fall has been shown to reduce density of mature and seeding chaff flower plants. Although a single prescribed fire had a direct impact on chaff flower it is unlikely that fire alone will reduce chaff flower spread.
Japanese chaff flower is a relatively new invader. Infestations should be reported to local county weed districts, the extension office, or a university weed science department. Infestations can also be reported on EDDMapS at www.eddmaps.org
EDDMapS. 2018. Early Detection & Distribution Mapping System. The University of Georgia — Center for Invasive Species and Ecosystem Health. Online: www.eddmaps.org; last accessed September 20, 2018.
Garrie, KM. 2017. Prescribed fire effects on the invasive species Achyranthes japonica in southern Illinois. MS Thesis. Dept. of Forestry, Southern Illinois University, Carbondale, IL.
Rathfon, R and E. Eubank. Achyranthes japonica (Miq.) Nakai Fact Sheet FNR 447. Purdue University. Online: www.extension.purdue.edu/extmedia/FNR/FNR-477-W.pdf
Schwartz, LM, DJ Gibson, and BG Young. 2016. Do plant traits predict the competitive abilities of closely related species? AoB PLANTS 8.
Schwartz, LM, KM Smith, C Evans, KL Gage, DJ Gibson, and BG Young. 2015. Ecology and Control of Japanese Chaff Flower. Fact Sheet. Online: https://bugwoodcloud.org/mura/rtrcwma/assets/File/Chaff_FactSheet.pdf
Schwartz, LM, DJ Gibson, and BG Young. 2016. Life history of Achyranthes japonica (Amaranthaceae): an invasive species in southern Illinois. Journal of the Torrey Botanical Soc. 143(2): 93-102.
Smith, KM. 2010. Invasion and management of Achyranthes japonica in a southern Illinois wetland. MS Thesis. Dept. Plant Biology. Southern Illinois Univ, Carbondale IL.
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