Bidens beckii (Water Marigold)
|Also known as:||Beck's Water Marigold, Beck's Marsh Marigold|
|Habitat:||sun; ponds, lakes, slow moving water|
|Bloom season:||July - September|
|Plant height:||4 to 6 inches above water|
|Wetland Indicator Status:||GP: OBL MW: OBL NCNE: OBL|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Flowers are solitary at the tip of an emergent stalk, the emerged portion rising up to 6 inches above the surface of the water. Flowers are 1 to 1½ inch across with (usually) 8 yellow rays (petals) that may be notched or toothed at the tip. The center disk is less than ½ inch wide, made up of 10 to 30 tiny yellow disk flowers.
Leaves and stems:
Leaves are opposite, occasionally whorled in 3s, and present both above and below the surface. Emergent leaves are simple and stalkless, lance to egg-shaped, ¾ to 1½ inches long with smooth edges or sharply toothed to varying degrees especially around the tip end.
Submerged leaves are finely divided into many thread-like segments (filiform), round to fan-shaped in outline, 1 to 2 inches in length. Intermediate leaf forms, transitioning between submerged and emerged leaves, are sharply toothed, lobed or cleft. Submerged stems can be up to 8 feet long with little branching, the emergent portion is rarely more than 6 inches long.
While most of the beggars-ticks (Bidens) have a strong affinity for wet places, B. beckii has abandoned the land for a life amongst the lilypads, and is the only aquatic member of the Aster family in Minnesota. Preferring shallow waters of lakes, ponds and slow moving river channels, mixed in amongst other emergent vegetation, it is likely not often noticed by the typical lake recreationist. Bidens beckii is known as Megalodonta beckii in many references.
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Photos courtesy Peter M. Dziuk taken on Lake Eleven in Kanabec County.
Have you seen this plant in Minnesota, or have any other comments about it?