In summer our thoughts turn for refuge to cooling streams and pond edges, and to memories of a spring blaze of marsh marigold and moving water. Early to bloom, and in lush leaf through summer, marsh marigolds (Caltha palustris) are a cold-hardy and water-loving perennial. They are also a native alternative to their diminutive lookalike, the highly invasive lesser celandine (Ficaria verna). Differentiating between the two plants is helpful to curb the spread of one, and to encourage the cultivation of the other.
Photography by Marie Viljoen.
Both marsh marigolds and lesser celandine have buttercup-perfect, iridescent yellow flowers that signal their kinship: they belong to the Ranunculus family. But in North America lesser celandine, a transplant from Europe (it is also occurs natively in North Africa and West Asia), has mastered the insidious creep, smothering regional swathes of riverside and forest floor, altering habitats as it spreads its low but impenetrable canopy. Lesser celandine’s invasive status is mostly associated with the Northeast, but it is moving into the Midwest and occurs in the Pacific Northwest, too. In places where it grows beside moving water, flooding carries parts of the plant downstream, where they take root.
Marsh marigold’s species name palustris means “of marshes.” Varieties of marsh marigold have an unusually wide native distribution, described as circumboreal: The plants occur across the northern part of the planet (boreal means north), in North America, Europe, and Asia. The plant’s flowers are larger and more showy than lesser celandine’s. In terms of function, marsh marigold can stabilize stream banks, forming mounded, clumping colonies over time. The flowers’ pollen and nectar are a rich food source for native pollinators, and small mammals and ducks eat the seeds.
Lesser celandine removal sidebar: The removal of lesser celandine is not easy. If you have a few clumps, remove them at once. By the time a carpet has formed, the task is daunting, and complicated. Methodical mechanical removal, by hand, is best (although difficult), and vigilance is essential. Personally, I cannot recommend glyphosate (usually sold as Roundup).
Why not use glyphosate? There is its implication in the evolution of so-called super-weeds, for one thing. And while the Environmental Protection Agency (EPA) considers glyphosate “not likely to be carcinogenic to humans,” the International Agency for Research on Cancer (IARC) does classify glyphosate as “probably carcinogenic to humans.” Quite the contradiction.
For your own rabbit hole research consider that the studies that the IARC relied on seem more in keeping with real-world situations and exposure than those employed on by the EPA. Glyphosate has been banned by California, and in 2020. New York banned the use of glyphosate on state property. Its use is especially problematic near water, or when associated with water tables (everything lands up in the water table). Glyphosate has been showing up in stream and air samples since 2011, and its knock-on effects on life forms other than the target-plant (from soil microbes to aquatic invertebrates) are being studied.
