A New Invasive to Watch For: Lesser Celandine
Kari Maxwell and Kate Howe, Midwest Invasive Plant Network
Lesser celandine (Ranunculus ficaria), also known as fig buttercup or pilewort, is a perennial, herbaceous flowering plant native to Europe, North Africa, Western Asia, and Siberia. It was introduced to the United States as an ornamental and, despite its invasive tendencies in 17 states, many colorful varieties are still widely available commercially. In Indiana, lesser celandine has been reported in Hendricks, Lake, Marion, Monroe, and Wayne Counties.
Lesser celandine completes its life cycle during the winter and spring. It consists of a basal rosette composed of kidney-to-heart shaped leaves that are tender, succulent, dark green, shiny, and stalked (Figure 1). The flowers of lesser celandine are a bright buttery yellow that is slightly darker in the center (Figure 2). Symmetrical flowers with 8-12 petals are borne on single delicate stalks that rise above the leaves. Fruiting heads of lesser celandine are round and composed of many hairy seeds, most of which are not viable. Fingerlike tubers produced by the roots are abundant and easily visible when pulled from the ground (Figure 4).
The digging habits of some animals may unearth and scatter the tubers. Well-meaning humans may also unearth and scatter tubers when pulling weeds. Flood events can spread lesser celandine to new sites. Lesser celandine is a spring ephemeral that spends much of the year as underground, thickened fingerlike tubers or underground stems. During winter leaves begin to emerge and photosynthesize; flowering occurs late winter through mid-spring and plants will be mostly gone by June.
When in bloom, infestations of lesser celandine appear as a green carpet dotted with yellow on the forest floor (Figure 3). Lesser celandine occurs in low, open woods, floodplains, meadows, and waste spaces. It seems to prefer sandy soils. The dense patches of lesser celandine are a threat to native plants and native plant diversity. It displaces early-blooming native plant species such as: bloodroot, harbinger-of-spring, wild ginger, trilliums, squirrel-corn, and Virginia bluebells, which provide important nectar, pollen, fruit, and seeds for native insect and wildlife species.
There are several varieties of lesser celandine, one of which is double-flowered with many petals and silvery mottling on the dark green leaves. Lesser celandine can be confused with a native species, marsh marigold (Caltha palustris) (Figure 5), which is found in wetlands (See comparison). Marsh marigold does not form a continuous carpet, nor does it produce tubers or bulbets. Take care in correct identification before performing any method of control.
The window for control of lesser celandine is small due to its short life cycle. Manual methods are possible for small infestations, but the use of systemic herbicide is more effective because it kills the entire plant, including roots, and minimizes soil disturbance. All methods will require persistence and repetition to be effective in the battle against lesser celandine.
New sightings of lesser celandine and other invasive plants can be reported to the Great Lakes Early Detection Network at www.gledn.org. Be sure to include photos of diagnostic features to assist with verification of your report.
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Figure 1. Lesser celandine. Photo from Mary Klunk from Five Rivers MetroParks, Ohio
Figure 2. Lesser celandine. Photo from Tom Borgman from Hamilton County MetroParks, Ohio
Figure 3. Lesser celandine. Photo from Danielle Haake from Litzsinger Road Ecology Center, Missouri
Figure 4. Tubers on roots of lesser celandine. Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Figure 5. Marsh marigold. Photo from Carol Spears via Wikimedia Commons
Figure 6. Compare lesser celandine and marsh marigold