Plant of the Week – February 8th 2021 – Ficaria verna (Lesser Celandine)

Ficaria verna Huds. Lesser Celandine, Pilewort.

The lesser celandine is a cheery plant in spring, with bright yellow buttercup-like flowers. Like the buttercups, it is a member of the Ranunculaceae. But buttercups have five petals and five sepals whereas the lesser celandine has nine or ten petals and only three sepals. Despite the similarity in their common names, it is not related to the greater celandine (Chelidonium majus), which belongs to a different family, the Papaveraceae.

It is said to have been William Wordsworth’s favourite flower. He wrote three poems with many verses about this species. Including

‘…..
There is a flower that shall be mine,
‘T is the little Celandine. ..’

Fig. 1 Ficaria verna Huds., syn. Ranunculus ficaria L. showing flowers with three sepals, underground tubers and achenes,  Fig. from book ‘Deutschlands Flora in Abbildungen’ 1796. Johann Georg Sturm (Painter: Jacob Sturm), Public domain, via Wikimedia Commons. https://upload.wikimedia.org/wikipedia/commons/1/1f/Ranunculus_ficaria_Sturm59.jpg

Four subspecies (subsp. fertilis, verna, ficariiformis and chrysocephala) occur in the UK. Subspecies fertilis and verna are both common and are native. The other two subspecies are rare and thought to be garden escapes, although Stace (2019) raises the possibility that ficariiformis may be native to SW England and the Channel Islands.

Fig. 2 Above: Three flowers at different stages of development. The undersides of the petals are tinged green. Left: in flower at Roslin Glen, Midlothian. © Chris Jeffree

F. verna is coming into leaf in our garden, and we lifted a small clump a few days ago (see Fig. 3). The main plant possesses numerous underground tubers and is surrounded by smaller off-spring with fewer tubers. These tubers can be detached very easily and show how the plant may easily be spread.

Fig. 3 Left. An uprooted plant in early February (left), surrounded by offspring (right). All with numerous tubers. © Chris Jeffree

Fig. 4. Left: bulbils in leaf axils of F. verna subsp. verna (Krzysztof Ziarnek, Kenraiz, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons). Right: Bulbils in leaf axils, and root tubers © Chris Jeffree

Some of the distinguishing features of the two native sub-species are listed in Table 1. In the field, after flowering, the presence or absence of axillary bulbils (Fig. 4) is said to be a good guide to their identification, but otherwise they are not easy to distinguish in the wild. An article in Nature in 1961 (Heywood and Walker), argued that floral characters were not reliable. As bulbil production is seasonal, this limits the opportunities for discriminating between the sub-species unless you have a good microscope and the aptitude for determining chromosome numbers or chloroplast counting. Sterile triploids (hybrids between these subspecies) with very small flowers are reported to be quite common.

The bulbil-producing tetraploid (subsp. verna) appears to be less fertile than the diploid as few mature achenes are produced and much of its pollen is not viable (Taylor and Markham. 1978). Marsden-Jones (1935) observed that reproduction in the tetraploid was almost completely vegetative.

Table 1 Distinguishing features of Ficaria verna subspecies fertilis and verna (Taylor and Markham 1958, Stace 2019)
 Ficaria verna subsp. fertilisFicaria verna subsp. verna
Ploidy (chromosome number)Diploid (2n=16)Tetraploid (2n=32)
Chloroplasts per stomatal guard cell13 – 1724 – 28
Aerial tubers (bulbils) in the axils of cauline leaves after floweringNonePresent
Position of cauline leaves on flowering stemsMostly in the lower 1/3 of the pedicelMostly in the upper 1/3 of the pedicel
Achene developmentMostly matureFew mature
Petal length x width (mm)10-20 x 2 -96 – 11 x 2 – 5
Leavesentireshallowly lobed
Habituprightspreading

Both these subspecies are widely distributed through Britain and Ireland (see Fig. 4 below)(though subsp. verna is less abundant, particularly in western areas) and their distributions and habitats are very similar – they both favour damp meadows and stream-sides, shady woodland edges and hedgerows). However, Stace (2019) reports that locally their occurrences are often mutually exclusive. Taylor and Markham (1958) comment that the diploid (ie. subsp fertilis) tends to be associated with old, undisturbed, deciduous woodlands and permanent pastures, whereas the tetraploid (subsp. verna) is particularly associated with disturbed ground, frequently as a garden weed. Braithwaite (2020) reviews evidence suggesting that subsp. verna is an introduction associated with the 19th century expansion of the horticultural trade. It would be interesting to explore the genetic similarities or differences between these subspecies.

Fig. 4 Distributions of Ficaria verna subsp. fertilis and verna in Britain and Ireland © Botanical Society of Britain and Ireland

R. ficaria flowers before trees come into leaf and dies back after flowering, lying dormant through summer drought until the following spring. Jeffree (1960) analysed phenological reports of the Royal Meteorological Society. The mean date of first flowering for 20 years of records from 1929 – 1948 was day 59 (i.e. 28th February). However, scrutinising data from different meteorological districts showed that earliest flowering occurred in the Republic of Ireland (day 40 – 8th February), while latest flowering occurred in Eastern Scotland (day 83 – March 24th) (compared with Western and Northern Scotland with day 68 and 76 –  March 9th and 17th respectively). Given the changes in climate since these data were collected, I wonder when this plant will be in flower near you.

Like other members of the Ranunculaceae the upper surface of the petals are conspicuous with a combination of glossy and matte areas (Fig. 5), caused by a combination of structural and pigmentation factors. A very smooth, pigment-filled upper epidermis is separated from the mesophyll below by intercellular air spaces. The epidermis acts as a thin-film reflector yielding the gloss, and also serves as a filter for light backscattered by the strongly scattering starch and mesophyll layers beneath, which yields the matte-yellow colour. The gloss attracts insect pollinators and reflects sunlight to the centre of the flower, heating the reproductive organs (van der Kooi et al. 2017). Such structures in flowers provide an inspiration for 3D printing of solar concentrators (Momeni and Ni, 2018).

Fig. 4. Glossy and matte areas of petals of Ficaria verna © Chris Jeffree

Uses
Studies of plant remains from the Isle of Colonsay (Inner Hebrides) dating from the Mesolithic period (7900 – 7600 BP) (Mithen et al., 2001) found charred fragments of enormous numbers (30 – 40000) of hazelnut shells (Corylus avellana) alongside roasting ovens. With them were substantial quantities of charred bulbils and tubers of F. verna. Evidence suggests that they were intentionally exploited at that time, and similar observations have been made at sites in Germany and Denmark (Kloos et al., 2016).

Other reports (e.g. Grieve, 1931) describe the boiled leaves as being eaten as a vegetable, and tubers being dried and ground into flour. There is also some mention of young tubers and leaves being eaten in salads for scurvy. However, beware of such uses as all members of the Ranunculaceae contain the glucoside ranunculin, which turns into the irritant toxin protoanemonin when the plant is wounded.  Ethnobotanical literature refers to lesser celandine’s use in the treatment of piles (recognised by its common name ‘pilewort’) following the doctrine of signatures that herbs resembling parts of the body may be used to treat ailments of that part. However, trying this treatment may not be a good idea as Yilmaz et al. (2015) report a case of acute liver toxicity from this treatment.

Invasiveness
Ficaria verna has been introduced to North America, where it has become invasive in woodlands. It has the dubious appellation of being ‘weed of the week’ on the US Forest Service website https://www.invasive.org/weedcd/pdfs/wow/lesser-celandine.pdf.

References

Braithwaite, ME 2020 The history and distribution of the bulbil-bearing Ficaria verna subsp. verna (Ranunculaceae) in Britain. British & Irish Botany 2(3), 215-222.

Grieve, M. 1931 A Modern Herbal | Celandine, Lesser (botanical.com)

Heywood, V & Walker, S. (1961) Morphological Separation of Cytological Races in Ranunculus ficaria L.. Nature 189, 604. https://doi.org/10.1038/189604a0

Jeffree EP. 1960. Some long-term means from the Phenological Reports (1891 – 1948) of the Royal Meteorological Society. Quarterly Journal of the Royal Meteorological Society, 86, 95-103.

Klooss S, Fischer E, Out W & Kirleis W. (2016) Charred root tubers of lesser celandine (Ficaria verna Huds.) in plant macro remain assemblages from Northern, Central and Western Europe. Quaternary International 404 A, 25-42,
ISSN 1040-6182, https://doi.org/10.1016/j.quaint.2015.10.014.

Marsden‐Jones, EM. (1935), Ranunculus ficaria Linn.: life‐history and pollination. Journal of the Linnean Society of London, Botany, 50, 39-55. https://doi.org/10.1111/j.1095-8339.1935.tb01501.x

Mithen, S., Finlay, N., Carruthers, W., Carter, S. & Ashmore, P. (2001) Plant Use in the Mesolithic: Evidence from Staosnaig, Isle of Colonsay, Scotland Journal of Archaeological Science 28, 223–234. doi:10.1006/jasc.1999.0536

Momeni, F & Ni J (2018) Nature-inspired smart solar concentrators by 4D printing. Renewable Energy, (122) 35-44, ISSN 0960-1481,https://doi.org/10.1016/j.renene.2018.01.062.

Stace, CA. (2019). New Flora of the British Isles (4th ed.). Middlewood Green, Suffolk: C & M Floristics. ISBN 978-1-5272-2630-2

Taylor, K. & Markham, B. (1978). Ranunculus ficaria L. (Ficaria verna Huds.; F. Ranunculoides Moench). Biological Flora of the British Isles. Journal of Ecology, 66(3), 1011-1031. doi:10.2307/2259310

van der Kooi CJ, Elzenga JTM, Dijksterhuis J & Stavenga DG. 2017 Functional optics of glossy buttercup flowers. J. R. Soc. Interface 14: 20160933. http://dx.doi.org/10.1098/rsif.2016.0933

Yilmaz, Bulent, Yilmaz, Baris, Aktas, B, Unlu, O & Roach, EC (2015) Lesser celandine (pilewort) induced acute toxic liver injury: The first case report worldwide. World Journal Of Hepatology 7(2), 285-288. DOI: 10.4254/wjh.v7.i2.285

Julia Wilson

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