This is perhaps an ecological disaster, but it is a gorgeous ecological disaster, and a woodland carpeted with celandine is not to be missed. The plant is a European import, not very common around here except in a few stream valleys, where it covers the ground so thickly that little else can grow. This vast colony grows in the Squaw Run valley in Fox Chapel, where it was blooming in the middle of April.
Gray describes the genus and the species:
RANÚNCULUS [Tourn.] L. CROWFOOT. BUTTERCUP. Annuals or perennials; stem-leaves alternate. Flowers solitary or somewhat corymbed, yellow, rarely white. (Sepals and petals rarely only 3, the latter often more than 5. Stamens occasionally few.) — (A Latin name for a little frog; applied by Pliny to these plants, the aquatic species growing where frogs abound.)
§ 1. FICÀRIA Boiss. Roots tuberous-thickened; sepals 3; petals about 8, yellow, with a free scale over the honey gland.
R. ficària L. (LESSER CELANDINE.) Glabrous and somewhat succulent; leaves basal on long stoutish petioles, ovate, rounded, deeply cordate, subcrenate; flowers scapose, 2 cm. in diameter. (Ficaria Karst.) — Wet places, occasional; Mass. to D. C. Apr., May. (Introd. from Eurasia.)