While giving a tour during Swarthmore College’s Family Weekend, I was questioned about a lovely little yellow-flowering groundcover in the garden. The visitor knew that one type of yellow flowering groundcover blooming this time of year was an invasive and should be removed immediately and another was a native to our woodland and should be allow to self seed into the garden. She knew she had either the invasive lesser celandine, Ranunculus ficaria, or the native celandine poppy, Stylophorum diphyllum, in her garden. The difference can easily be distinguished between the two plants if you know what you are looking at.

Ranunculus ficaria in bloom. photo credit: R. Robert

Ranunculus ficaria is a carpet-like groundcover with heart-shaped leaves which flowers with buttercup-like flowers in March and April. Lesser celandine creates a mat of vegetation often in floodplain areas preventing other native plants from emerging and sprouting in the spring. The foliage dies back in mid-summer leaving bare ground until it reemerges in early spring. Vast swathes of this plant can be seen along Crum Creek.

Ranunculus ficaria carpeting the floodplain all the Crum Creek. photo credit: R. Robert

It is believed this invasive was introduced as an ornamental plant from Europe, as European horticulturists have been developing cultivars since the late 1500s. When removing this garden thug, be sure to dig up all the small bulblets to prevent its return.

Stylophorum diphyllum in bloom. photo credit: R. Robert

Stylophorum diphyllum also sports a yellow flower in April, but the foliage it distinctly different. Celandine poppy or wood poppy has deeply incised, hairy leaves – reminiscent of an oak leaf. A native of the United States this perennial grows well in shade to part-sun and favors a woodland setting with rich soils along steam banks. The foliage of S. diphyllum does not create the same matting effect as R. ficaria, thus it doesn’t prevent the emergence of the other spring ephemerals.

S. diphyllum also produces an attractive bristly fruit for garden interest. The foliage will disappear by mid-summer like R. ficaria. There is lovely stand along the Cedar Lane sidewalk on the outskirts of the Cherry Border.

If you have R. ficaria in your garden, be sure to dig it out while the vegetation is still visible. If you have S. diphyllum enjoy the color and texture it brings to the garden by allowing it to naturalize.