All of our species of Bidens like to hang out near water. This one goes all in. Water-marigold grows in still or slow-moving water, with less than a foot of flowering stem sticking up. Below water, according to Wiki, the stems can be a couple of meters long. But the deepest growing stems recorded here in Michigan were in 4.6 meters of water. In 1980, a careful analysis of the features of water-marigold made a persuasive case that it should be separated into the genus Megalodonta, and it became M. beckii. Within the last few years, analysis of its molecular phylogeny brought it back to Bidens. You can't always believe your eyes! Water-marigold grows in CT(T), IA(E), ID, IL(E), IN(E), MA, MD, ME, MI, MN, MO, MT, NH, NJ(E), NY(T), OH(X), OR, PA(E), RI, VT, WA, WI, BC, MB, NB, NS, ON, QC, and SK. Lenawee Co MI, 6/13/12. The species is believed to have been extirpated from Ohio. This one was growing nine miles north of that border. Don't give up Ohio! Aster family, Asteraceae.