Lesser Celandine

''Ficaria verna'' (formerly ''Ranunculus ficaria'' ), commonly known as lesser celandine or pilewort, is a low-growing, hairless perennial flowering plant in the buttercup family Ranunculaceae native to Europe and Western Asia. It has fleshy dark green, heart-shaped leaves and distinctive flowers with bright yellow, glossy petals.Functional optics of glossy buttercup flowers
Journal of the Royal Society Interface 14:20160933Buttercups focus light to heat their flowers and attract insects
New Scientist 25 February 2017 It is now introduced in North America, where it is known by the common name fig buttercup and considered an invasive species. The plant is poisonous if ingested raw and potentially fatal to grazing animals and livestock such as horses, cattle, and sheep. For these reasons, several US states have banned the plant or listed it as a noxious weed. It prefers bare, damp ground and is considered by horticulturalists in the United Kingdom as a persistent garden weed; nevertheless, many specialist plantsmen, nursery owners and discerning gardeners in the UK and Europe collect selected cultivars of the plant, including bronze-leaved and double-flowered ones. Emerging in late winter with flowers appearing late February through May in the UK, its appearance across the landscape is regarded by many as a harbinger of spring.

Description

Lesser celandine is a hairless perennial plant to about 25 cm high, growing in clumps of 4-10 short stems, on which the leaves are spirally-arranged or all basal. The leaf stalks have sheathing bases, no stipules, a groove along their upper surface, and two hollows within. The leaves are cordate, 1-4 cm across, dark-green above with a distinctive variegated or mottled pattern, and pale green below. Purple-leaved varieties are common. The margins of the leaves are sometimes entire (rounded) but more often angled or weakly lobed, with hydathodes at the tips. There are two types of roots: dense clusters of thick, pale-coloured elongated tubers surrounded by patches of short, fibrous roots. Some clumps give rise to long stolons to 10 cm or more, allowing vegetative spread to produce extensive carpets of plants.

It produces large actinomorphic (radially symmetrical) flowers, up to 3 (or even 5) cm diameter, on long stalks arising individually from the leaf axils or in loose cymes at the top of the stem. There are no bracts. The flowers have a whorl of 3 sepaloid tepals and 7 to 12 glossy yellow petaloid tepals, which are sometimes tinged purple or grey on the back. Double flowered varieties also occur. The stamens and carpels are numerous, and the fruit is a single-seeded, shortly hairy achene with a very short style. In several subspecies, tubers are formed in the leaf axils after flowering. It blooms between March and May in the UK.

Distribution

''Ficaria verna'' ''sensu lato'' is native to central Europe, north Africa and the Caucasus. It is not native in North America.

Life cycle

Lesser celandine grows on land that is seasonally wet or flooded, especially in sandy soils, but is not found in permanently waterlogged sites. In both shaded woodlands and open areas, ''Ficaria verna'' begins growth in the winter when temperatures are low and days are short. The plants mostly propagate and spread vegetatively, although some subspecies are capable of producing up to 73 seeds per flower. Germination of seeds begins in the spring, and continues into summer. Seedlings remain small for their first year, producing only one or two leaves until the second year.

Growth and reproduction is poor in dry or acidic conditions, though the plants can handle drought well once dormant. By emerging before the forest canopy leafs out, ''Ficaria verna'' is able to take advantage of the higher levels of sunlight reaching the forest floor during late winter and early spring. By late spring, second year plants quickly age as daylight hours lengthen and temperatures rise. By the end of May, foliage has died back and plants enter a six month dormancy phase.

If disturbed, separation of the plant's numerous basal tubers is an efficient means of vegetative propagation. The plants are easily spread if the prolific tubers are unearthed and scattered by digging activities of some animals and humans. Erosion and flood events are particularly effective means of spread, as the plants are very successful at colonizing low-lying floodplains once deposited.

''Ficaria verna'' exists in both diploid (2n=16) and tetraploid (2n=32) forms which are very similar in appearance. However, the tetraploid types prefer more shady locations and can develop up to 24 bulbils at the base of the stalk. Subspecies ''F. verna ''ssp''. verna,'' and ''F. verna ''ssp''. ficariiformis'' are tetraploid and capable of colonizing new areas much faster because they produce bulbils in their leaf axils in addition to root tubers. Subspecies ''F. verna calthifolia'' and ''F. verna verna'' are diploid and hybrids between subspecies often create sterile triploid forms.

Ecology as an invasive species

In many parts of the Eastern and Northwestern United States and Canada, lesser celandine is cited as an invasive species. It poses a threat to native wildflowers, especially those ephemeral flowers with a spring-flowering lifecycle. Since ''Ficaria verna'' emerges well before most native species, it has a developmental advantage which allows it to establish and dominate natural areas rapidly. It is mainly a problem in forested floodplains, where it forms extensive mats, but can occur on upland sites as well. Once established, native plants are displaced and ground is left barren and susceptible to erosion, from June to February, during the plant's six-month dormancy phase.

In the United States, where lesser celandine is considered a plant pest to gardens, lawns, and natural areas, many governmental agencies have attempted to slow the spread of this species with limited success. As of 2014, the species was reported to be invasive and established in 25 states. USDA APHIS considers ''Ficaria verna'' to be a high risk weed which could spread across 79 percent of the United States, anticipating possible impacts to threatened and endangered riparian species. The U.S. National Park Service's Plant Conservation Alliance recommends avoiding planting lesser celandine, and instead planting native ephemeral wildflowers such as ''Asarum canadense'', bloodroot, the native twinleaf (''Jeffersonia diphylla''), and various species of ''Trillium'' as alternatives.

As a garden plant

Christopher Lloyd is one of several horticulturists who have recommended one of the double-flowered Flore Pleno Group for planting at the base of a hedge next to a lawn. ''The Daily Telegraph'' has even given advice on how to plant them, provided by the Royal Horticultural Society. Double-flowered plants were noted as long ago as 1625 when one was found by John Ray. The RHS specialist quarterly publication ''The Plantsman

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