The Variable Marsh Marigold

Marsh Marigolds are one of the first plants that I like to hunt out on the Somerset Levels every spring. My favourite accessible site is in the middle of a marshy field. This field always floods in winter. Somerset fields are often surrounded by watercourses known as rhynes (see previous blog). There are often also ditches and shallow channels that run through fields called grips. It is just such a site that makes it possible for me to observe Marsh Marigolds closely without toppling headfirst down the slippery slopes of a rhyne.

Variation

My annual, spring marsh pilgrimage has given me the opportunity to observe differences in the flowers from year to year. I noticed that the flowers were much smaller this year than last year. There has certainly been quite a contrast between last year’s early spring and the frostier start to 2021. My reading reveals that noticing variation in Caltha palustris is nothing new.

The variation has led to taxonomists to delimit and present species, subspecies and varieties differently. Taxonomic confusion has reigned down the ages, for example:

• Schott, Nyman and Kotschy (1854) recognised 6 species: C. cornuta, C. latifolia, C. laeta, C. intermedia, C. vulgaris, and C. alpestris. 
• Beck (1886) recognised 5 species with varieties delimited in a different way to the above authors, but again relied on the plant’s follicles for determination.
• Huth (1892) lumped species back together, described transitional species, but nonetheless ended up with 14 varieties.
• Reese (1954) and Turin (in Heywood c.s., Flora Europaea I, 1964) apparently threw in the towel and declared that a satisfactory classification of the varied forms of Caltha palustris was difficult to achieve.

Smit (1973) relates how controversial and dubious divisions continued. Her own research revealed strong fluctuations in plant size. Lowland plants were very large with multiple, large flowers and leaves and thick stems. Upland habitats revealed dwarf plants with few flowers. Upland and lowland plants grown in the same experimental conditions over 3 years reduced the divergence and appeared increasingly similar. It seems that the jizz (overall appearance) is more reliable than measurements in species delimitation.

Smit does not stop with plant size. She observes huge variations in leaf size, leaf margins, sepal colour, number of tepals and carpels. Such variation is seen not only within the same plant community but also on the same plant. As to the follicles that have played such a key determining role down the ages, well, the author concludes that they should be dismissed as too variable to be reliable characteristics.

Names

Not only is the Marsh Marigold highly variable in morphology, it also boasts a whole suite of different common names. Grigson devotes a page and a bit to recording all the UK county variations in The Englishman’s Flora. Somerset volunteers much of that variation without even looking at other counties. Maybe 35 names are a bit over the top even for Somerset?

Botanical Latin name

Thank goodness for Linnaeus and the dependability of a single Latin name per species. Unfortunately, that has not stopped a multitude of other names being created down the ages. World Flora Online lists 6 accepted varieties and a total of 122 synonyms that include subspecies and varieties. Kew’s Plants of the World Online list 100 synonyms. Taxonomists never seem to agree.

The Marsh Marigold goes by the Latin botanical name of Caltha palustris L. The L. designator after any plant name refers to Linnaeus. The genus name Caltha is variously taken to mean yellow flower and later goblet from Ancient Greek. It describes the goblet-like shape of the flower, which is also captured in popular vernacular names like Kingcup. The epithet palustris describes the plant’s predilection for a marshy habitat.

Adaptable Survivor

Caltha palustris is a member of the Ranunculaceae or Buttercup family. It is a primitive, early flower that is believed to have taken advantage after the Ice Age to spread. It has a wide distribution across the world. It handles the cold, erratic, early spring weather well. It is one of the first flowers to provide early nectar for pollinators. A wide range of pollinators seek it out. It is not dependent on any one pollinator or even any one method of pollination. It can even be pollinated by rain. No wonder the Marsh Marigold is such a survivor. Such variability and adaptability should stand it in good stead to confront future extreme weather conditions under climate change too.

Easy to Identify

Despite all the variability and complications noted above, the Marsh Marigold is an easy flower to identify for beginner botanists. There is not really another flower that you could confuse it with and its yellow flowers call out in springtime from its marshy habitat. Why add complications to such a delightful flower?

Gallery of Images

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Marginal Habitat

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Previous Blog

What is a Somerset rhyne?

References and Further Reading

• Avalon Marshes (?): Water and Drainage.
• Easy Wildflowers (2014): Caltha palustris, The Marsh Marigold. 30 December 2014
• Grigson, Geoffrey (1975): The Englishman’s Flora. Helicon. Oxford.
• Hagerup, O. (1950): Rain-pollination. Royal Academy, Copenhagen, Denmark.
• Harris, Stephen (1985-2021): Plant 173. Caltha palustris L (Ranunculaceae) Marsh marigold. Oxford University Plants 400.
• Haslam, Sylvia & Sinker, Charles & Wolseley, Pat (2013): British water plants. FSC Publications. Telford.
• Kew Science (2021): Caltha palustris L. Plants of the World Online.
• Smit, Petra G. (1973): A Revision of Caltha (Ranunculaceae). Blumea 21 (1973) 119-150
• Stace, Clive (2010): New Flora of the British Isles. Third Edition. Cambridge
• Streeter, David et al (2016): Collins Wild Flower Guide. 2nd Edition.
• World Flora Online (WFO) (2021): Caltha palustris L.

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Karen does not seek or receive any commercial interest or advantage from this blog. She is not promoting any business venture. She simply loves to share fascinating facts about plants. These pages illustrate her love of plants, botany, biodiversity, gardens and creative expression. There is always so much to learn about plant diversity. This blog is designed as a showcase for photography, commentary on plants and wildlife, gardens and other places visited, horticulture and related topics. Viewpoints are her own, not those of her employer.

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