New addition to Wisconsin’s prohibited species list

Along with garlic mustard and browsing herbivores, a new threat to our native woodland flora is lesser celandine (Ranunculus ficaria) which grows as an herbaceous groundcover with kidney to heart-shaped leaves and showy, daisy-like yellow flowers.  The species rapidly reproduces and spreads into new areas through bulbils, tubers and viable seed (up to 70 seeds per plant). 

The plant begins growing soon after snow melt.  After flowering in March and April, aerial vegetation dies back and entire plants can be dead by June. This provides a very narrow window for which to search, identify and control this invader.

Lesser celandine thrives in partial sun and moist soils, but also tolerates drier, sunny sites.  Poisonous to livestock and humans, the plant invades forests, wetlands, river ways and uplands including pasturelands and residential lawns making it an enemy of farmers, homeowners and natural area managers alike. 

Infestations of lesser celandine threaten spring ephemeral communities in woodlands, eliminating our sensitive native plants.  Natural area managers in Ohio and other northeastern states have been struggling with managing this plant for many years.  In one Cleveland park, approximately 400 acres are dominated by lesser celandine.  Wisconsin Species Assessment Groups were assembled recently to recommend a legal classification for each new species considered for NR 40 (Wisconsin’s Invasive Species Rule). The recommendation for lesser celandine was based upon a literature review developed by the department.

Mechanical control includes hand-digging individual plants, being careful to remove all bulblets and tubers.  Hand-digging is difficult in larger populations due to the high degree of soil disturbance and abundance of small tubers which are not removed when you just pull the plant.  It is very important to monitor the site in subsequent years for residual plants.  Herbicide treatments must be carried out early in the spring, prior to the emergence of native spring ephemerals and amphibians.  Glyphosate herbicide (e.g., Roundup®) applied to foliage at the standard 1.5% dilution of the concentrate is effective for control.  That is 2 oz. of the 40-50% glyphosate concentrate per gallon of water.  If you get in the habit of mixing a dye in the herbicide you use for foliar spray, you will never want to go back to spraying herbicide without dye again

SEWISC is currently partnering with the Wisconsin Department of Natural Resources (WDNR) and two landowners in our region to control populations of lesser celandine.  Help us identify any additional populations in southeastern Wisconsin to expedite early detection and rapid response efforts by reporting any populations of this invading plant immediately to the WDNR.