Bidens beckii (Water Marigold)

Plant Info
Also known as: Beck's Water Marigold, Beck's Marsh Marigold
Genus:Bidens
Family:Asteraceae (Aster)
Life cycle:perennial
Origin:native
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):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 7+petals

[photo of flower] 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.

[photo of bracts] The 5 to 8 outer bracts are hairless and spreading with several vertical lines, oblong or wider at the tips and are about half the length of the petals.

Leaves and stems: Leaf attachment: opposite Leaf attachment: whorl Leaf type: lobed Leaf type: simple

[photo of emersed leaves] 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.

[photo of submersed leaves] 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.

Notes:

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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More photos

Photos courtesy Peter M. Dziuk taken on Lake Eleven in Kanabec County.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Susan - Itasca County, near Dora Lake
on: 2014-06-26 14:17:40

A few years ago, my husband & I saw it while driving, we stopped to look, and then looked it up in our wildflower book. It says something like "it grows in quiet waters" And indeed they were, it was a small boggy area off in the woods, very lovely to see. Also, saw pink lady slippers nearby, right next to the road. I wonder if they are still there?

Posted by: Nancy - Little Toad Lake, Becker County
on: 2016-08-31 13:14:48

Found this on our lakeshore this morning growing among yellow water lilies. This is the first aquatic aster I've seen -what a treat!

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