fireweed

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

• noun Any of various plants of the genus Epilobium, especially E. angustifolium (syn. Chamerion angustifolium), having long, terminal, spikelike clusters of pinkish-purple flowers.
• noun Any of several weedy North American plants of the genus Erechtites in the composite family, having small white or greenish flowers grouped in discoid heads.

from The Century Dictionary.

• noun The jimson-weed, Datura Stramonium; also, occasionally, D. Tatula.
• noun The wild lettuce, Lactuca Canadensis.
• noun The golden ragwort, Senecio aureus.
• noun In botany: The Erechthites hieracifolia, a coarse annual composite of North America, so called from its appearing abundantly where clearings have recently been burned over.
• noun The great willow-herb, Epilobium angustifolium, for the same reason.
• noun The horseweed, Erigeron Canadensis.
• noun A species of plantain, Plantago media.

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

• noun An American plant (Erechthites hiercifolia), very troublesome in spots where brushwood has been burned.
• noun The great willow-herb (Epilobium spicatum).

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

• noun A perennial herbaceous plant (Epilobium angustifolium) in the willowherb family Onagraceae.

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

• noun tall North American perennial with creeping rootstocks and narrow leaves and spikes of pinkish-purple flowers occurring in great abundance in burned-over areas or recent clearings; an important honey plant
• noun an American weedy plant with small white or greenish flowers