Japanese knotweed (Fallopia japonica), native to Eastern Asia, was introduced to North America in the late 1800s as an ornamental plant. This plant is found in most U.S. states, and many countries worldwide, exhibiting invasive behavior outside of Asia*.
Japanese knotweed was identified in Vermont as early as the 1920s**. In the wake of Tropical Storm Irene, Vermont specific research was conducted on treatment methods for Japanese knotweed. Below are the citations for the results of that work, published in scientific journals in 2014 and 2015.
Identifying Japanese knotweed can happen year round. In the early spring, look for shoots of dark red, that almost look like asparagus. In the late spring and summer, zigzagging canes can grow up to 10’ tall. Leaves are alternately arranged, and are a spade/heart shape. In the late summer, tiny white flowers emerge in sprigs trailing down each stem. In the fall and winter, when the plant has gone dormant, the aboveground portion of the plant dies, but takes time to decompose. As a result, rusty yellow-orange stands can start to appear (see picture). Decomposition continues through the winter, and the color becomes less obvious.
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*Distribution table, http://www.cabi.org/isc/datasheet/23875
**Art Gilman, 1999. Flora of Caledonia County, Vermont. Rhodora 101: 360-414.
Scientific papers focused on Japanese Knotweed in Vermont:
Brian P. Colleran and Katherine E. Goodall (2015) Extending the Timeframe for Rapid Response and Best Management Practices of Flood-Dispersed Japanese Knotweed (Fallopia japonica). Invasive Plant Science and Management: April-June 2015, Vol. 8, No. 2, pp. 250-253.
Brian P. Colleran and Katherine E. Goodall (2014) In Situ Growth and Rapid Response Management of Flood-Dispersed Japanese Knotweed (Fallopia japonica). Invasive Plant Science and Management: January-March 2014, Vol. 7, No. 1, pp. 84-92.
Japanese knotweed factsheet:
http://www.vtinvasives.org/sites/default/files/knotweed2010.pdf
A compendium of information regarding Japanese knotweed, worldwide focus:
http://www.cabi.org/isc/datasheet/23875
Photo Credit: E. Spinney, December 2015, Essex Junction, VT, Japanese knotweed
Article Credit: E. Spinney, VT FPR