By Addie Brown, 2025 CCC Corps Member
Invasive species pose a significant threat to ecosystem biodiversity and health, and ACLT has been dedicated to addressing this issue through land stewardship initiatives for decades. Throughout the year, ACLT staff and volunteers work tirelessly to identify and remove these species, helping protect the ecological balance of our forests. To stay ahead of emerging invasive threats, ACLT’s land management staff has implemented Early Detection and Rapid Response (EDRR) surveys as part of the new Invasive Species Control Plan. Through this initiative, ACLT staff developed a list of high-priority species likely to become new invaders on ACLT-owned and managed land.
With spring just beginning, now is the time to search for two invasive spring ephemeral species of particular concern: Ficaria verna (lesser celandine) and Corydalis incisa (incised fumewort). While these invasive species have not yet been found on ACLT property, the Maryland Biodiversity Project reports that incised fumewort has been identified in Howard, Montgomery, and Washington counties, and lesser celandine has been found in the surrounding counties of Prince George’s, Anne Arundel, and Charles. Populations of both species are spreading rapidly in these areas, making early detection and control even more important. Catching these species early is vital to preventing their establishment on ACLT land and stopping their spread before they can cause significant ecological damage.
Lesser celandine, a perennial native to Europe, Asia, and northern Africa, was introduced to the U.S. from Europe, likely for ornamental purposes. First identified in Pennsylvania, it has since spread across the Northeast, Missouri, and the Pacific Northwest. Typically found along streams and rivers in open floodplain forests and wetlands, lesser celandine thrives in moist, sandy soils. These environments allow this species to grow and reproduce quickly, enabling it to form dense mats that cover the forest floor. Lesser celandine can be identified by its yellow, 8- 12 petaled flowers, long-stalked peduncle (main stem), and glossy, kidney-shaped leaves. This plant’s small, finger-like tubers (modified stems) spread underground, while small white bulbils (clones of the parent plant) extend from the stem after flowering.
These reproductive structures enable this species to reproduce both sexually and asexually, which contributes to its rapid spread and dominance in new areas. Lesser celandine typically emerges in late February to early April and dies back around June. Since it surfaces before many native spring ephemerals, lesser celandine can quickly take over, preventing other plants from developing and reproducing, leading to significant disruptions in ecosystems and affecting wildlife that depend on native plant communities. When it dies back, lesser celandine leaves bare patches that are vulnerable to further invasion by other invasive species.
Due to its bulbils and underground tubers, removal of lesser celandine is challenging. While it can be removed manually, care must be taken to ensure all tubers are fully extracted from the soil, as any tubers left behind may grow into new plants. Removed plants should be bagged to prevent the spread of the tubers and bulbils.
Herbicide application in early spring, when the plant is first emerging, can also be an effective control method. When searching for lesser celandine, note that Caltha palustris (marsh marigold) closely resembles it. This perennial is native to Maryland and is also found in wetland habitats. However, marsh marigolds have more rounded flower petals and larger, toothed leaves.
Incised fumewort is a biennial or annual herbaceous plant native to East Asia, including countries such as China, Korea, Japan, and Taiwan. It was first identified in the U.S. in 2005 in Bronx County, New York, and has since spread throughout the eastern U.S. to states including Pennsylvania, Washington D.C., Virginia, Maryland, West Virginia, and North Carolina. It has also been reported in Illinois and Tennessee. Incised fumewort is often found in disturbed areas, particularly near waterways and floodplains. It thrives in mesic (moist) forest areas that are subject to periodic flooding and prefers alluvial soils, which are formed from sediment – such as sand, silt, clay, and organic matter – deposited by waterways. This invasive species can be identified by its bilaterally symmetrical purple flowers and compound leaves that are divided into three serrated leaflets and then into three sub-leaflets. The plant’s stems typically emerge in February, with blooming occurring from March through early May.
Approximately three weeks after blooming, the plant disperses seeds and enters a period of dormancy, with only a rosette of leaves reemerging in the fall. Like lesser celandine, incised fumewort dominates the understory, displacing native species and threatening ephemeral plant communities. The plant’s explosive seed dispersal method and preference for wetland areas make it particularly concerning, as its seeds can spread through surrounding waterways.
Additionally, ants are attracted to the plant’s elaiosomes – oil-producing structures on the seeds – which can further aid in its spread.
To effectively manage incised fumewort, it should be removed before the seed capsules mature. Manual removal, including hand-pulling and digging, is recommended. Several sources suggest removing this invasive species as a second-year plant, rather than a first-year plant. This is likely to avoid breaking off underground tubers of the weaker first-year plants, which could lead to regrowth and further spread. A second-year plant can be identified by its upright stem that supports multiple branched leaves, while first-year plants typically have only a few leaves that remain close to the ground. Similar to lesser celandine, removed plants should be placed in a bag to reduce the chance of spreading seeds and tubers. Herbicide application is also a potential control method, though proximity to waterways should be considered. When searching for incised fumewort, note that Corydalis flavula (yellow corydalis), a native species, closely resembles it. Like incised fumewort, yellow corydalis has leaflets; however, they are more lobed and less deeply divided. Additionally, yellow corydalis has yellow flowers, while incised fumewort has purple flowers.
As temperatures rise and trails become busier this spring, ACLT staff encourage you to keep an eye out for lesser celandine and incised fumewort. Early detection is essential for controlling their spread before they become a significant threat.
To learn more about Spring ephemerals (both native and non-native), sign up for our Spring Ephemerals Guided Hike scheduled for Sunday, April 13, 2025 beginning at 10am at the North Side Trailhead. Click here to register. Space is limited! Sign up today!
References
Liisma. (n.d.). Incised fumewort (Corydalis incisa). Liisma. https://liisma.org/incised-fumewort-corydalis-incisa/
Maryland Department of Agriculture. (n.d.). Corydalis incisa weed risk assessment with Maryland filter. https://mda.maryland.gov/plants-pests/Documents/Corydalis%20incisa%20WRA%20with%20MD%20Filter.pdf
Maryland Department of Natural Resources. (n.d.). Mid-Atlantic invasive plant species: The lesser celandine. https://dnr.maryland.gov/wildlife/Documents/midatlantic.pdf
Maryland Invasive Species Council. (2017, May 1). An incisive invader: Incised fumewort (Corydalis incisa). https://mdinvasives.org/iotm/may-2017/
Minnesota Department of Agriculture. (n.d.). Lesser celandine. Minnesota Department of Agriculture. https://www.mda.state.mn.us/lesser-celandine
New York Botanical Garden. (n.d.). Invasive plants: Corydalis incisa. https://libguides.nybg.org/invasiveplants/corydalis_incisa_display
New York Invasive Species Information. (n.d.). Lesser celandine. https://nyis.info/species/lesser-celandine/#origin
Solem, J. (n.d.). Species: 3034 – Maryland biodiversity project. Maryland Biodiversity Project. https://www.marylandbiodiversity.com/species/3034
Solem, J. (n.d.). Species: 17581 – Maryland biodiversity project. Maryland Biodiversity Project. https://www.marylandbiodiversity.com/species/17581#:~:text=Media%20by%20Joanne%20Solem.,Source:%20Wikipedia
University of Maryland Extension. (n.d.). Lesser celandine. https://extension.umd.edu/resource/lesser-celandine/
Wisconsin Department of Natural Resources. (n.d.). Lesser celandine (Ranunculus ficaria). https://dnr.wisconsin.gov/topic/Invasives/fact/LesserCelandine
