Menyanthes trifoliata L., Bogbean
Account Summary
Native, common and widespread. Circumpolar boreo-temperate.
1882; Stewart, S.A.; Co Fermanagh.
April to November.
Growth form and preferred habitats
An emergent aquatic or semi-aquatic glabrous perennial with a creeping rhizome, Menyanthes trifoliata used to be considered a member of the Gentian Family, but it has now been transferred to the Menyanthaceae, a small family of five genera and 40 species, all of which are aquatic (Preston & Croft 1997). Whatever its relationships or taxonomy, M. trifoliata has to be one of the most strikingly beautiful wild flowers in the flora of B & I.
It is a significant member of numerous marsh, fen and bog plant communities on the shallow margins of lakes, pools and ditches, where, depending on depth, it occasionally forms either single-species stands around the edge of open water in lakes and tarns, or floating mats in deeper water further offshore. In poor- to medium-nutrient fen-meadow conditions, or in slow-flowing drains of similar nutrient status, it is more usually associated with a wide range of other common emergent shoreline species such as Carex rostrata (Bottle Sedge), Equisetum fluviatile (Water Horsetail), Galium palustre (Marsh-bedstraw), and Potentilla palustris (Marsh Cinquefoil).
M. trifoliata also commonly occurs in shallow, acidic, nutrient-starved pools on raised or blanket bogs, or in cut-over versions of these, where it is frequently accompanied by species such as Eriophorum angustifolium (Common Cottongrass) and Potamogeton polygonifolius (Bog Pondweed). Few plants can compete with the vigorous growth of Bogbean on deep, oxygen-deficient (anaerobic), organic mud or peat. It can also be found on the wettest areas of moorland flushes, which being fed with ground water are of slightly richer nutrient status and where also root aeration is very much better than in the surrounding ground (Hewett 1964; Preston & Croft 1997).
Fermanagh occurrence

Bogbean is a very common, widespread and locally abundant species in Fermanagh as the tetrad map emphasises, having been recorded in 242 tetrads, 45.8% of those in the VC. It is particularly common, indeed omnipresent, around the shallows of Upper Lough Erne and other inter-drumlin lakes. It is also frequent in pools and flushes on raised and blanket bogs, except at the highest levels.
Flowering reproduction
The deciduous, fleshy, trifoliate, bean-like leaves are overtopped by a thick, short raceme of up to 29 flowers on a leafless stalk or peduncle from May to July (Hewett 1964). The corolla tube, broadly campanulate, c 15 mm diameter, has five deep recurved lobes, the petals being rose pink on their outer surface, pure white on the inner, 'much fribriate', which is the technical botanical shorthand describing the incredibly beautiful, deeply-cut, lace-like fringing, which makes the flower so remarkable it really becomes unforgettable (Clapham et al. 1962; Hewett 1964). The early British herbalist, John Gerard described the flower very poetically in language of Shakespeare's time as, "... towards the top of the stalks standeth a bush of feather like flowers of a white colour, dashed over slightly with a wash of light carnation" (Gerard 1597).
It is difficult to imagine why the Bogbean petals are so deeply fringed, or indeed why any flower should be so decorated (eg Dianthus superbus (Fringed Pink) or Gentiana ciliata (Fringed Gentian)). One possibility is the fringe may deter small crawling insects, too small to effect pollination (Melderis & Bangerter 1955). Or does it perhaps play some part in a water-pollination mechanism (ie hydrophily), as in other aquatics such as Najas spp., Callitriche hamulata (Intermediate Water-starwort) and Ceratophyllum spp. (Faegri & van der Pijl 1971)? The fringe might somehow enable rain-pollination, where the flower fills with water to a certain level and pollen grains float on the surface until they eventually reach the stigma (Hagerup 1950).
These latter suggestions are ruled out by the fact that M. trifoliata flowers are self-incompatible (Hewett 1964) and, furthermore, they exist in two forms, 'pin' and 'thrum', ie they are dimorphic heterostylous, like Primrose (Primula vulgaris) and Cowslip (P. veris), having styles and filaments of two different lengths, a very positive out-breeding mechanism (Nic Lughadha & Parnell 1989; Proctor et al. 1996; Richards 1997a).
The flowers secrete nectar at the base of the globular ovary and attract a variety of small insects that act as pollinators (Garrard & Streeter 1983). In an Irish study, on average, 17 ovules were produced per flower and, on average, six seeds developed, although seed production was found to be very uneven. Thirty-five percent of sampled capsules contained no ripe seed whatsoever (Nic Lughadha & Parnell 1989).
Seed dispersal
While fruit set may well be rare and the number of seed produced few (Hewett 1964; Nic Lughadha & Parnell 1989), seed dispersal, even as an occasional event, is of vital importance to the long-term survival of the species. Water-borne dispersal is bound to be significant and, as expected, Bogbean seed is hard coated and extremely buoyant, the seed-coat integument containing, "aeriferous tissue with intercellular spaces" (Ravn 1894), so the seeds can often float for up to two months and remain viable, or rarely longer than this (Sculthorpe 1967). According to Hewett (1964), however, many seeds are still buoyant and remain viable when kept in water for up to 15 months. The current author (RSF) finds the latter claim rather incredible, and would like to see the detailed data on which it is based before fully accepting it.
Aerial seed travel after capsule dehiscence is a very short distance. Nic Lughadha & Parnell (1989) measured distances in the field that ranged from 4 to 49 cm, with a mean of only 16.3 cm.
Since M. trifoliata is regularly recorded in isolated lakes and tarns, the plant must be capable of some additional form of jump-dispersal. Birds, particularly Mallard ducks, have been implicated in observations reported by Ridley (1930) and, as some of these birds migrate, seeds in their crop might be transported, especially those with a resistant testa like that of Bogbean.
Experimental studies on seed dispersal by fish involving M. trifoliata are also described by Ridley (1930). The fish mentioned include Roach and Perch. Ridley even moots the remote possibility of fish with seed in their gut being taken and transported by birds, chiefly ducks, including Mallard. This might seem a tad ridiculous as a mechanism, but there is plenty of evidence from island biogeography that proves long-distance or jump-dispersal does occur in Nature (Carlquist 1974) and generally it is a process involving the highly improbable to overcome the otherwise impossible!
Vegetative reproduction
Probably like other common and successful rhizomatous species, eg Calystegia sepium subsp. sepium (Hedge Bindweed) and Tussilago farfara (Colt's-foot), Bogbean seed production is of secondary importance to vegetative reproduction, except in terms of long-distance transport and long-term species evolutionary survival. Vigorous rhizome spread is a highly successful means of transport for a species living in a less-than-ideal nutrient environment. Indeed, vegetative reproduction tends to become of paramount importance in every environment where survival is severely tested, such as arctic, alpine and desert conditions. Bogs and acidic waters fed by runoff from siliceous, nutrient-poor rocks, also provide such a testing environment and clearly M. trifoliata must be well-adapted to cope with the problem of competition for scarce resources.
Fossil record
The British fossil record of M. trifoliata is remarkable for its extensiveness and completeness (Godwin 1975). The seeds are regarded as the most easily recognised Quaternary plant fossils, but pollen and rhizome fragments are also found. It occurs in both full-glacial and early post-glacial deposits (Hewett 1964).
Bogbean appears on a list of 34 ancient aquatic plants native in the British Isles, all represented in late-glacial sediments, some of them possibly periglacial survivors (ie species considered to have been present in the near vicinity of major ice sheets during the glacial phase(s)) (Sculthorpe 1967). Confirmation of the periglacial presence of M. trifoliata in Ireland comes from a study of a site at Derryvree, near Maguiresbridge, Co Fermanagh, where a fossil seed of the species was recovered in a Middle Midlandian full glacial deposit radio-carbon dated to 30,500 BP. This deposit contained a flora and fauna of open tundra, and a periglacial climate prevailed when it was laid down (Colhoun et al. 1972).
Of the ancient aquatic species listed by Sculthorpe (1967), only two do not currently appear in Fermanagh, Scheuchzeria palustris (Rannoch-rush) (extinct at its previous solitary site in Co Offaly (H18)) and Subularia aquatica (Awlwort), an extremely rare plant in Ireland with post-1970 records from just four hectad squares (Preston & Croft 1997).
British and Irish occurrence
M. trifoliata is a common, locally abundant plant in B & I, most prevalent in the N & W of both major islands, although it has suffered centuries of depredation in the S & E due to drainage and development, so that in those parts of the country it has become scarce or absent (New Atlas).
Possessing such a beautiful flower, it is not surprising that M. trifoliata is regularly cultivated in water gardens. In turn, this can lead to plant material either escaping, or the excess being irresponsibly dumped in the wild. Burton (1983) believed that some occurrences of Bogbean in the London area originated in this manner and the same could very easily occur elsewhere. In Middlesex (VC 21), where Bogbean was previously local, it has become rare, and Kent (1975) believed that on numerous occasions it had been deliberately planted in semi-wild situations.
European and world occurrence
M. trifoliata belongs to the circumpolar boreo-temperate phytogeographical element. The main area of distribution lies in the northern boreal region, between 40°N and the Arctic Circle. The southern limit of the range lies between C Portugal and Spain, S France, Corsica, N Italy, Greece, the Caucasus into temperate Siberia and on to Japan. It has also been recorded in N Morocco. In N America, the southern limit of the distribution runs from California in the west to Maryland in the east. It grows N of the Arctic Circle in W Greenland, Iceland, Norway, Siberia and Alaska (Hewett 1964; Hultén & Fries 1986, Map 1510).
Uses
Apart from its decorative use in water gardens, Bogbean contains a small quantity of volatile oil and a bitter glucoside called 'Menyanthin' that makes it very unpalatable. It is possibly this feature that has made it one of the most prized herbs available to folk use and herbal medicine (Allen & Hatfield 2006). M. trifoliata has been used in herbal folk medicine as an astringent tonic and for a variety of ailments including digestive problems, rheumatism, constipation, arthritis, scurvy, asthma, persistent coughs, pulmonary tuberculosis, fevers, jaundice and kidney trouble. A decoction of the root has also been used to relieve pain of stomach ulcers and the leaves were used as a poultice for boils and skin troubles (Grieve 1931; Vickery 1995; Allen & Hatfield 2006).
In other uses, the leaves, being bitter, have been used in the past in N England as a substitute for hops in beer-making and hence the local name 'Bog Hop' (Grigson 1955, 1987). The rhizome has also been dried and powdered for use as a substitute for bread flour by Esquimaux, and also in N Eurasia (Mabberley 1997).
Names
The genus name, 'Menyanthes' originated with the Greek herbalist, Theophrastus, who appears to have given it to the related aquatic, Fringed Water-lily (currently Nymphoides peltata). The word elements of the name are, 'mene' in Greek meaning 'moon' or 'month', and 'anthos', 'a flower' (Johnson & Smith 1946; Gledhill 1985). The suggestion, applied to M. trifoliata, is that the flowering period lasts one month, but in reality, the flowering phase continues for three months of the summer.
The English common name 'Bogbean' is a late 18th century modification of 'Buckbean', the 16th century name translated by Henry Lyte (1578) from the Flemish 'Bocksboonen' in the herbal of Rembert Dodoens (1554). Lyte took this to mean 'Goat's beans', the leaves resembling young leaves of the Broad Bean (Grigson 1974). 'Buckbean' was eventually transformed to 'Bogbean', presumably to better fit the typical habitat and become more comprehensible.
Threats
None.