USDA’s Animal and Plant Health Inspection Service (APHIS) has published a risk assessment for incised fumewort, Corydalis incisa (syn. Fumaria incisa Thunb.). The report was initiated as the result of a newspaper article featuring the plant.
Native to China, Korea, Japan and Taiwan, the plant was first discovered outside of cultivation in the U.S. in Bronx County, New York, in 2005. It has since been observed throughout the East Coast from New York to Pennsylvania, Maryland, Virginia, West Virginia and Tennessee.
According to the APHIS report, it is not clear how C. incisa was introduced to the U.S., but speculation is that it was initially imported as an ornamental, “given the horticultural interest in the genus.” Despite reports of the plant having become a popular ornamental, researchers/authors report that they found “no evidence that it is commonly cultivated.”
The risk assessment provides detailed information on impact potential, geographic potential and entry potential. Because of its relatively recent discovery, the plant scores very high on the “uncertainty” scale for impact. However, the study states that about 37 percent of the U.S. is suitable for establishment of C. incisa, given its known distribution in other countries. Factors that appear to favor its spread include USDA hardiness zones of 6 to 10 and areas with annual average precipitation of 20 to 100 inches. Köppen-Geiger climate classes that favor C. incisa include humid subtropical, marine west coast, humid continental with warm summers, and humid continental with cool summers. Geographically, that would include states from the Eastern Seaboard through the Great Plains, and spotted areas along the Pacific Northwest.
Entry potential is rated 0.58 on a scale of 0 to 1, where 1 represents the maximum likelihood of introduction. Because C. incisa is related to a popular ornamental, “additional material of this species would enter the United States [as] plants for planting,” according to the report.
Corydalis incisa is an annual or biennial, spring-ephemeral herb growing 4 to nearly 20 inches tall. Seeds germinate in the spring and develop small rosettes, which wither during the summer. They emerge again as rosettes throughout the winter and produce compact flowering racemes the following spring. Leaves are stalked and twice pinnately compound with acutely serrate leaflets. Racemes are about 1 to 5 inches tall and bear up to 24 rose-purple, .5- to .75 – inch-long flowers. Tiny seed are borne in oblong capsules.