lesser celandine

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A Eurasian plant (Ranunculus ficaria) in the buttercup family, having heart-shaped leaves, solitary yellow flowers, and tuberous roots.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A European perennial herb, Ranunculus ficaria, having heart-shaped leaves and solitary yellow flowers

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun perennial herb native to Europe but naturalized elsewhere having heart-shaped leaves and yellow flowers resembling buttercups; its tuberous roots have been used as a poultice to relieve piles