yellowtop

from The Century Dictionary.

• noun A reed-grass, Calamagrostis hyperborea Americana, common in low meadows and on shady river-banks throughout the northwestern United States. It affords a large yield of hay, excellent if cut in season.
• noun Same as early goldenrod.
• noun A variety of turnip: so called from the color of the skin on the upper part of the bulb.

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

• noun (Bot.) A kind of grass, perhaps a species of Agrostis.

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

• noun Any of the genus Flaveria of plants with yellow flowers, related to the sunflower.