Japanese hedge parsley is considered a winter annual (germinating in fall) or a biennial. The first year plants have finely divided fern-like leaves in a rosette near the ground. White umbel flowers develop into small seeds with burrs that catch on fur and clothing. Fall and winter is a good time to search for this plant since the rosettes that germinate in fall remain green and overwinter under the snow.
Check out these links for further information on Japanese hedge parsley:
Wisconsin Department of Natural Resources
Midwest Invasive Plant Network
For more information on this new threat or to learn about others, visit Wisconsin Department of Natural Resources.