Purple autumn crocus or colchicum.
autumn crocus definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
colchicum (sense )
autumn crocus definition by American Heritage Dictionary
A corm-producing European and North African plant (Colchicum autumnale) having showy colorful flowers that appear in the fall. Also called meadow saffron.