Each spring we welcome the return of abundant flowers and cherish them as they lift our spirits. Unfortunately, some of these beautiful plants have proven to be aggressive and ultimately highly unwanted.
Look out for this one!
One such menace is Lesser celandine (Ranunculus ficaria) which displaces more desirable plants in lawns, gardens, parks, and natural areas. Mowing and tilling control more well-behaved weeds, but only causes lesser celandine to spread further. Entire lawns, parks, and even neighborhoods have been taken over!
What does it look like?
To identify this plant, look for its bright and shiny yellow flowers that hover on 6-8 inch stems over a sea of glossy kidney to heart-shaped green leaves. They are, indeed, quite pretty. This plant only blooms for a few weeks in late winter or early spring and then its flowers and leaves quickly wither away.
Why is it so bad?
During this critical period, it can prevent growth of native and ornamental plants in gardens and natural areas by shading and by secreting growth-suppressing chemicals into the soil. These adaptations allow it to out-compete more desirable plants, reducing diversity and aesthetics in your garden. It does best in damp, disturbed areas, but is competitive in many locations. Lesser celandine is also toxic to most mammals, including humans and livestock.
Lesser celandine shouldn’t be confused with marsh marigold (Caltha palustris), which is native to other parts of Oregon and has similar flowers but grows taller and less aggressively.
How do I control it?
To get rid of this weed, we recommend that you carefully dig up these plants and dispose of them as trash. Be sure not to lose track of its finger-like bulbs that easily separate and establish new plants. For large infestations, herbicides with active ingredients of glyphosate and triclopyr are effective when applied soon after the plant starts flowering.
Caution with chemicals!
It is critically important to apply according to the label instructions and to only apply in allowed settings. Consider hiring a state-licensed herbicide applicator. You will also benefit from establishing and promoting competing vegetation. Learn more about how to control lesser celandine.
Jeff Lesh works in the WeedWise Program at the Clackamas Soil and Water Conservation District. Find additional invasive weed information on our WeedWise page.