Meaning of water marigold in English:
water marigold
noun
1Marsh marigold, Caltha palustris, or any of several other plants of the genus Caltha (now rare).
2A yellow-flowered aquatic bur marigold of North America, Bidens beckii, which is highly sensitive to water pollution and hence used as an indicator species.
Origin
Early 19th century; earliest use found in John Sinclair (1754–1835), agricultural improver, politician, and codifier of ‘useful knowledge’.
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