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Lathraea squamaria L., Toothwort

Account Summary

Native, occasional to uncommon, local. European temperate.

1866-72; Smith, T.O.; White Park, Ardunshin.

March to June.

Growth form and preferred habitats/hosts

Toothwort is a monoecious, bisexual, total parasite, a white or pale grey, scaly, fleshy 'ghost' of a plant. A rhizomatous perennial lacking any green chlorophyll pigment, it obtains all of its nutrition by its branched, creeping, rather stout rhizome attacking and robbing the roots of woody plants, primarily Corylus avellana (Hazel) and Acer pseudoplatanus (Sycamore), but also on Cherry Laurel (Prunus laurocerasus), Portugal Laurel (P. lusitanica) and other members of the Rosaceae, plus Ulmus glabra (Wych Elm) (although presumably limited now by the elm decline of the 1970s), Alnus glutinosa (Alder) and Sambucus nigra (Elder). Much less frequently it can also occur on Rhododendron spp. (Rhododendron), Salix spp. (Willow), Populus spp. (Poplar), Fagus sylvatica (Beech), Tilia spp. (Lime) and on conifers including Picea spp. (Spruce) and Chamaecyparis lawsoniana (Lawson's Cypress) (Colgan & Scully 1898; Hackney et al., 1992; Sell & Murrell 2009). Note that this list of hosts is a compilation of numerous sources researched by the current author (RSF) and does not imply that L. squamaria has been found associated with all of them in Fermanagh.

Toothwort generally skulks at the base of host trees in the dark shade of woodland thickets, but occasionally is more apparent by the sides of paths in damp woods (see also below). It is essentially a lowland plant, although it reaches 350 m at Alston in Cumberland (VC 70) (M.J.Y. Foley, in: Preston et al. 2002).

Fermanagh occurrence

L. squamaria has been recorded in 33 Fermanagh tetrads, 6.3% of those in the VC. It is an occasional and very local species and its Fermanagh habitats are typical of the species, being in moist woods, scrub, hedgerows, streamsides and riverbanks, mainly in limestone districts but it does also appear on richer, more fertile humus soils (Clapham et al. 1962, 1987; Sinker et al. 1985). As the local tetrad map indicates, it is thinly and widely scattered across Fermanagh, but is most frequent in the SW of the county from Florencecourt to Belcoo. 

Flowering reproduction

The plant flowers in early spring before the leaves expand on the host tree(s) on whose roots it grows. The perfect (hermaphrodite) two-lipped flowers, 15 mm long and 6 mm in diameter are produced in crowded, one-sided, spike-like raceme on a stem 10-20 cm tall, tend to be a dirty mauve or pink stained grey-white in colour, and are not particularly tooth-like in appearance (see below). Nectar is abundant; the flowers are pollinated by bumble-bees in April and May and the plant has completed its reproduction and disappeared below ground by the middle of July (Garrard & Streeter 1983). The flowers are at first insect pollinated, but if this fails to occur, then a tendency towards wind pollination develops (Hutchinson 1972).

The fruit capsule, 8-10 mm, is ovoid, acuminate at its apex. The seeds are very small, 1-2 mm, subglobose, reticulate, black and numerous (Butcher 1961; Sell & Murrell 2009). They have an attached oil- or food-body (elaiosome) of the Viola odorata (Sweet Violet) type, which rewards and encourages ants to come and help disperse the seeds (Ridley 1930).

Irish occurrence

In the past, Toothwort has been recorded in 33 or 34 of the Irish VCs, but in some areas of the island it is either very rare or extinct. The 1976 edition of the BSBI Atlas included many pre-1930 records, especially in the S & W of Ireland (Perring & Walters 1976; Scannell & Synnott 1987; Webb et al., 1996). However, the New Atlas hectad map, based on recording in the period 1987-1999, indicates the species is widely but thinly scattered across most of the island, with a greater presence in some northern counties, especially Fermanagh (H33), Armagh (H37) and Antrim (H39) (Preston et al. 2002).

British occurrence

In Britain, L. squamaria is also widespread, scattered and decidedly local in England and Wales, chiefly on moist, fairly base-rich or chalky soils. In England, where there has been unexplained decline, it is regarded as a rather good indicator of ancient (pre-1600) woodland, appearing in eleven out of 15 species lists collated by K.J. Kirby in 2005, tabulated and presented in Proctor (2013). However, it cannot be said that the presence of any particular rare species on its own indicates that the woodland is ancient (Proctor (2013)!

In Scotland, L. squamaria is rather thinly scattered south of a line between Glasgow and Edinburgh, becoming much scarcer northwards. The species reaches its most northerly Scottish outlier in East Ross (VC 106) (McCallum Webster 1978; New Atlas).

European and world occurrence

L. squamaria is mainly restricted to mid-latitudes in Europe. In the Iberian Peninsula, it does not extend much further south than Bilbao and Barcelona and it is absent from all the Mediterranean isles with the exception of Sicily. To the north, it reaches S Norway and S Sweden. Eastwards, it extends to C Russia and it also has some outliers in the Himalayan region (Hultén & Fries 1986, Map 1705). The distribution of Toothwort mirrors that of its most common host, Corylus avellana, at least to some extent (Hultén & Fries 1986, Map 627).

Names and uses

The genus name 'Lathraea' is from the Greek 'lathraios' meaning 'hidden' or 'secret', probably referring to the shady sites it generally occupies and its brief seasonal appearance. The Latin specific epithet 'squamaria' is from 'squama' meaning 'a scale', referring to the scaly appearance of the underground rhizome and the aerial flowering branches (Melderis & Bangerter 1955; Gilbert-Carter 1964).

The English common name 'Toothwort' is thought to come from the old herbal 'Doctrine of Signatures', whereby the scale-leaves on the underground stem and the base of the plant resemble teeth (Prior 1879; Grigson 1974). Even more aptly, the ivory-white, shiny fruit capsule is much more tooth-like and thus the plant might have been considered useful, if it were not so scarce, to alleviate tooth ailments (Grigson 1955, 1987). Rather surprisingly, despite its suggestive appearance, Toothwort never seems to have caught on as a significant herbal remedy and it is seldom mentioned in herbals. Gerard (1597, 1633) found that country women called it 'Lungwort' and used it against coughs and "all other imperfections of the lungs". However, even he was very sceptical of this report.

Grigson (1955, 1987) lists one other interesting name, 'Corpse-flower', from Yorkshire. This is not listed in Britten & Holland (1886), but Watts (2000) does include it, suggesting that the name derives from the lack of chlorophyll and the whitish appearance of the fleshy aerial stems. In N America, Monotropa uniflora (Yellow Bird's-nest) is sometimes called 'Corpse Plant' for the same reason (Watts 2000).

There is no reference to Toothwort at all in the Modern Herbal of Grieve (1931) and, very probably, this reflects the relative scarcity of the plant and its brief, early season appearance, both of which help keep it out of easy reach of herbalists (Mabey 1996). Herbalists might also be put off by the fact that the fleshy tissues of the plant turn black on drying (Clapham et al. 1962, 1987).

Threats

None locally.

References

Clapham, A.R., Tutin, T.G. and Warburg, E.F. (1962 & 1987); Perring, F.H. and Walters, S.M.(eds.) (1976); Scannell, M.J.P. and Synnott,D.M. (1987); Ridley, H.N. (1930); Webb,D.A., Parnell, J. and Doogue, D. (1996); Hackney, P.( Ed.) and Beesley, S., Harron, J. and Lambert, D. (1992); Colgan & Scully 1898; Prior, R.C.A. (1879); Grieve, M. (1931); Grigson, G. (1974); Grigson, G. (1955, 1987); Gerard (1597, 1633); Britten & Holland (1886); Watts (2000); Melderis & Bangerter 1955; Gilbert-Carter 1964; Hultén & Fries 1986; McCallum Webster 1978; New Atlas; Proctor (2013); Garrard & Streeter 1983; Sell & Murrell 2009; Mabey 1996; Hutchinson 1972; Butcher 1961; Sinker et al. 1985;