Have you seen incised fumewort (Corydalis incisa)? This frilly, little wildflower is surprisingly invasive. Originally from East Asia, this species has been spreading southward along the I-95 corridor from New York since 2005. The first iNaturalist observations of incised fumewort in Maryland were made in the spring of 2018. As of this writing, Maryland contains 259 Research Grade observations. Many gardeners report that the seeds must have been present in potted plants or mulch that they purchased. In our parks, incised fumewort quickly outcompetes native spring wildflowers, and particularly dramatic declines in Virginia bluebells have been observed in the Bull Run floodplain (Northern Virginia).
Incised fumewort came into bloom in mid-March this year and normally continues blooming until early April. Seeds ripen within three weeks of blooming. Ripe seeds are explosively dispersed up to 10 feet away from their parent plants. They may also be dispersed by flowing water, tracked mud. Some reports indicate they are dispersed by ants.
Gardeners and landscape maintenance professionals tell us that manual control is unreliable at best. In some cases, even very persistent, frequent episodes of manual control have failed. Chemical control is more effective, but has its own challenges, such as unintended damage to nearby native plants.
In either case, it helps to understand that the species is biennial. The flowers of second-year plants are easy to see, but seedlings are inconspicuous. If management only targets flowering plants, that can be a viable strategy. But for folks who didn’t realize there were also seedlings present, it can be shocking to see that despite all your hard work there are even more flowering plants the next year. This gives the impression that management is failing, which may or may not be true. My casual observation is that seedlings (dicotyledons present) germinate in both spring and fall. I suppose the spring germinators go dormant for the summer and re-emerge in fall while the other seeds are germinating. The resulting rosettes are fully evergreen. The rosettes have a small, soil-colored tuber. For those of you doing manual control, make sure to remove it.
You can help by reporting this plant when you see it. You can do that quickly and easily using the iNaturalist app. Just point, click, and upload. There is even a space there where you can leave us some notes. Your observation will contribute to a publicly available map that is used by many land management agencies and their volunteers (Weed Warriors) to prevent new infestations from becoming established.
If you would like to read more about incised fumewort biology, a native look-alike, and making iNaturalist reports, check out this article by the National Park Service.
By Sara Tangren, Ph.D., Environmental Program Coordinator, National Capital PRISM, Metropolitan Washington Council of Governments. This article was published originally in the University of Maryland Extension IPM Alert, March 22, 2024.