day lily

from the GNU version of the Collaborative International Dictionary of English.

• any plant of a genus of plants (Hemerocallis) closely resembling true lilies, but having tuberous rootstocks instead of bulbs. The common species have long narrow leaves and either yellow or tawny-orange flowers, which often bloom for only one day.
• A genus of plants (Funkia) differing from the last in having ovate veiny leaves, and large white or blue flowers.

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

• noun Alternative form of daylily.

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

• noun any of numerous perennials having tuberous roots and long narrow bladelike leaves and usually yellow lily-like flowers that bloom for only a day
• noun any of numerous perennials having mounds of sumptuous broad ribbed leaves and clusters of white, blue, or lilac flowers; used as ground cover