Caltha natans (Floating Marsh Marigold)

Plant Info
Also known as:
Genus:Caltha
Family:Ranunculaceae (Buttercup)
Life cycle:perennial
Origin:native
Status:
  • State Endangered
Habitat:part shade, sun; shallow slow-moving water; streams, sheltered bays, pools, swamps, ditches, beaver ponds, muddy shores
Bloom season:June - August
Plant height:2 to 10 inches
Wetland Indicator Status:GP: none MW: none 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: 5-petals Cluster type: raceme

[photo of flower] Flowers are stalked, single or in loose clusters of 2 to 6 at the tip of the stem and arising from some leaf nodes. Flowers are about 3/8 inch across, have 5 white to pinkish petal-like sepals, and yellow stamens surrounding a dense cluster of 20 to 40 green pistils in the center.

Leaves and stems: Leaf attachment: alternate Leaf type: simple

[photo of leaves] Leaves are alternate, 1 to 2 inches long, as wide as or wider than long, kidney to heart-shaped, rounded at the tip, hairless, and long-stalked. Edges are toothless to variably scalloped and may be wavy. Stems are slender, hairless, prostrate, root at the nodes and can reach lengths of 1 to 3 feet. In shallow water, stems and leaves are mostly floating, the flower clusters rising just a few inches above the water's surface. Landlocked plants are creeping.

Fruit: Fruit type: capsule/pod

[photo of developing fruit] The cluster of pistils becomes a hemispheric head of capsules, known as follicles, each 1/8 to ¼ inch long, oblong with a curved beak at the tip and containing tiny brown seeds.

Notes:

Floating Marsh Marigold is a circumboreal species, native to Eurasia and North America, but rare south of the Canadian border. In Minnesota, it is known from a handful of populations in St. Louis and Koochiching counties, and only known from a single county in each of Michigan and Wisconsin, often in beaver ponds. According to the DNR, like many aquatic species it suffers from habitat loss and degradation and was listed as Endangered in 1996.

It is unlikely to be confused with any other species; the combination of long-stalked kidney to heart-shaped leaves, stems that are creeping or floating and rooting at the nodes, and 5-petaled white flowers single or in loose clusters of 2 to 6 should be distinctive.

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More photos

Photos by John Thayer taken in St. Louis County.

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