Pedicularis palustris L., Marsh Lousewort
Account Summary
Native, frequent. European boreo-temperate, very probably an introduction in eastern N America.
1881; Stewart, S.A.; Co Fermanagh.
March to December.
Growth form and preferred habitats
This species is a stiff, erect leafy annual or biennial hemi-parasite of somewhat pyramidal form that attaches itself, xylem to xylem, to the roots of grasses, sedges and other herbs and extracts water and mineral solutes from its host. As is the case with the related Rhinanthus minor (Yellow-rattle), there is no evidence of the parasite benefitting from acquisition of phloem-borne photosynthates from its host (Westbury 2004). P. palustris has stems that grow up to 60 or 70 cm, but usually less than this; it branches freely and produces deeply cut, bipinnate leaves 30-50 mm long, all of which characters distinguish it from the closely related P. sylvatica (Lousewort), which is a shorter perennial with fewer, prostrate branches and leaves that are only 15-20 mm long (Webb et al. 1996). The stem leaves can be partly opposite and partly alternate. P. palustris also has a calyx that is pubescent and the upper lip of the dull red corolla has four teeth. In comparison, the calyx of P. sylvatica is glabrous and the upper lip of the corolla has just two teeth (Garrard & Streeter 1983).
These two red-flowered Lousewort species are partial- or hemi-parasites, possessing chlorophyll and displaying both autotrophic and heterotrophic nutrition. The current author's (RSF's) account of Rhinanthus minor on this website provides more details of the benefits and consequences of partial parasitism on species and vegetation. The poverty of the pasture caused by the partial parasitism of this and other related species has led to the charge against these plants of producing lice in sheep grazing them and hence the English common name 'Lousewort' (Melderis & Bangerter 1955).
Marsh Lousewort is also known as Red Rattle since the leaves and stems of the plant are very often a bright red or dark purple colour, indicating a phosphate or a nitrogen mineral deficiency. It is a good indicator of situations where there is mobile ground water (ie lateral and/or vertical water movement) and a moderate to poor supply of mineral nutrients, making the name 'Marsh Lousewort very appropriate (Sinker et al. 1985). P. palustris tolerates a wide range of wet soil conditions, from acid to neutral, or less commonly calcareous base-rich, over clay or peat, but it most usually frequents rather acid soils and can do so at altitudes up to 860 m. It is a plant of valley bogs, wet heaths, wet meadows, fens, stream sides and hillside flushes, in fact almost anywhere acidic with a variable water table (Garrard & Streeter 1983; Sinker et al. 1985). The thing it most definitely does not tolerate, is shade.
Flowering reproduction
P. palustris produces large, tubular, bisexual flowers 25-30 mm long, in short, terminal leafy racemes from May to September. The flowers are shortly stalked (nearly sessile) in the axils of the upper leaves, but they eventually form, especially when in fruit, a ± dense, if rather short, truncated, spike-like appearance. The calyx lobes are much shorter than the inflated and reticulate tube. The calyx is large with two broad, irregularly toothed lobes that are hairy outside. The 2-lipped, laterally flattened corolla is tubular and longer than the calyx, deep purple-red or reddish-pink in colour, the upper lip, narrowly hood-like and with two very small teeth on each side of the hood. Following Proctor & Yeo (1973) description, but not word for word, "The corolla hood encloses the four stamens with the stigma just protruding between them from the underside near the tip. The lower lip of the corolla has two large side lobes and a smaller middle lobe, forming a flat, but obliquely angled landing platform for insect visitors. The two pairs of stamens face one another in the confines of the corolla hood and the pressure of the sides of the hood keeps them pressed together, preventing the released pollen from escaping." (Proctor & Yeo 1973; Garrard & Streeter 1983).
Pollination mechanism
Based on Proctor & Yeo's description of the mechanism, the "visiting bee or bumble bee grasps the base of the obliquely slanting lower lip of the corolla with its forelegs and the corolla tube just below the lip with its middle legs. Holding onto the flower, it then inserts its head into the widest part of the entrance to the hood, touching the club-like stigma that protrudes obliquely downwards from between the anthers; in the process, pollen is transferred from a previous flower visit."
As the insect probes for the deeply hidden nectar secreted at the fleshy base of the ovary within the tubular corolla and calyx, "it prises apart the sides of the corolla hood, at the same time drawing forward the upper part of the hood and releasing the pressure on the stamens, allowing released pollen to fall from between them and rain down onto its head". (Hutchinson 1972; Proctor & Yeo 1973).
Fruit and seed
The fruit capsule is 15-17 mm, ovoid, compressed and curved, longer than the calyx. The seeds are few, large, 2.5 × 1.6 mm, oblong, coarsely reticulate and brown in colour (Butcher 1961). They lie in the bottom part of the capsule, which when dry rattles with them when it is shaken (Sell & Murrell 2007). Salisbury (1942) examined only a few plants but found the number of capsules per plant ranged from 27 to 400, with a mean of 165 capsules. The contents of 30 capsules ranged from 6 to 20 seeds with a mean of 12. He calculated from this that the mean seed output would be around 1,980 per plant.
As might be expected, seed dispersal involves wind and water: wind to shake the rather tall stems, sufficiently strong, not just to rattle the capsules, but to eject the large seed, which weigh an average of 1.48 gm (Salisbury 1942). Since P. palustris plants either stand in water in marshy ground, or are growing near water, a proportion of the seeds may often land in water, where they can float for from one to six months (H.B. Guppy, quoted in Ridley 1930). [No date given for Guppy, but Ridley lists a total of six references by this author. The six references are rather briefly, and probably inadequately, listed for our purposes.] The seeds possess an air-cell structure in the seed coat that enables floatation (F.K. Ravn 1894, quoted in Ridley 1930).
Seeds germinate in the spring and early summer (Fitter 1987).
o the European
Godwin (1975) lists the fossil finds of P. palustris seeds recorded from two English sites dating from the Middle Weichselian ice age, and additional records, "from zones I & III of the Late Weichselian in Kent and the Isle of Man and from zone IV of the Flandrian [the current warm interglacial period] in Northumberland. Finally, there is a Roman record from Newstead." He goes on to comment, "The fossil record strongly indicates periglacial survival in Britain", ie the species was present during the glacial stage, living near the ice ('peri' means 'around') (Godwin 1975).
Fermanagh occurrence
In Fermanagh, P. palustris has been recorded in 98 tetrads (18.6% of the VC total) and 86 of them have post-1975 records. Typical habitats are marshy ground ranging from wet meadows to fens, to flushes on bogs and stream-sides. As the tetrad distribution map shows, Marsh Lousewort is widespread throughout Fermanagh, on lakeshores, especially around both sections of Lough Erne, on the Western Plateau and in the extreme SE of the county.
P. palustris occurs frequently in the Lough Erne water meadows where it has to be able to tolerate both light grazing pressure and trampling by cattle. It grows vigorously forming distinct bushy plants in short, more or less flooded grazed grassland, but it also manages to persist and grow tall and spindly (up to 100 cm), even amid relatively tall tussock grass and sedge vegetation in wet ground.
British and Irish occurrence
Although P. palustris remains widely distributed throughout B & I, it has become very rare in C & SE England, but common in the N & W. There have been major population losses on both islands stretching over since the 1960s and 1970s, largely due to drainage for agriculture and for urban or agricultural development (F.J. Rumsey, in: Preston et al. 2002). Some losses are probably also the consequence of neglected, wet lowland alluvial areas becoming overgrown by scrub (Brewis et al. 1996). In parts of S England, eg along the Thames valley, P. palustris has become a rarity of ancient wet meadows on nutrient-rich soils and is now on the verge of local extinction, or has actually become extinct (Crawley 2005).
European and world occurrence
Belongs to the European boreo-temperate phytogeographical element and is mainly restricted to Europe. It extends throughout temperate middle latitude Europe southwards to the Pyrenees, N Italy, S Bulgaria, S Urals and the Caucasus. The plant in B & I is subsp. palustris, and a northern subspecies, subsp. borealis (Zett.) Hyl. replaces it in N Europe. A related species extends the distribution eastwards into C Asia and Siberia (P. karoi Freyn). P. palustris has been recorded in eastern N America, but it is very probably an alien introduction there (Hultén & Fries 1986, Map 1694; Sell & Murrell 2007).
Uses
Previously, Pedicularis sylvatica (Lousewort), P. palustris and Rhinanthus minor (Yellow-rattle), being closely allied to the Euphrasia spp., Eyebrights, were used in herbal medicine, but as remedies they have now fallen into disuse. In the late 18th century, the Rev. Dr John Walker visited the island of Jura in the Hebrides and discovered a large number of inhabitants were crippled for life by a disease allegedly caused by a reddish worm, about an inch (2.5 cm) in length, which lodged under the skin of the knees or the ankles, causing intense pain. The affliction was known by the Gaelic name of 'Fillan', and cases were recorded from elsewhere in the Hebrides and Western Highlands by other early authors. The only known local cure was to take the root of what Walker (an experienced botanist and scientist) later identified was P. palustris, pound it and mix it with the marrow of beef bones or goat tallow. This was applied on a hot poultice to the part of the body affected (Allen & Hatfield 2004). The root was used externally against lice and internally to treat infestations of worms (Walker 1764, 1771).
It is now known that P. palustris contains a glycoside called 'aucubin' which is an effective insecticide (Darwin 1996), supporting the above story.
Names
The genus name, 'Pedicularis' is derived from the Latin 'pediculus' , 'a louse' (Johnson & Smith 1946) and the species get their 'Lousewort' common name from the old belief (or myth) that, "it filleth sheep and other cattle, that feed in meadows where this groweth, full of lice" (Gerard 1597). 'Red Rattle' refers to the ripe seed rattling inside the base of the capsule and, also, the colour of the flowers (Prior 1879). The Latin specific epithet 'palustris' means 'of swampy places'.
In addition to 'Marsh Lousewort' and 'Red Rattle' Grigson (1966, 1987) lists ten more English common names several of which are shared with Rhinanthus minor, eg 'Cock's Comb' (from a superseded specific epithet of the latter, 'Crista galli'). Other interesting names for P. palustris include 'Cow's wort' and 'Deadmen's bellows', to the latter Grigson adds "(ie pillies, male members)", a reference the current author (RSF) does not comprehend. Three names make mention of nectar as 'Honey-cap', 'Honeysuckle' and 'Wild Honeysuckle'. There is also 'Suckies', from sucking the honey. A pair of the names listed refer to the wet ground habitat, 'Moss-crop' (ie 'moor') and 'Moss-flower'. There is, of course, the notion of seeds rattling in the dry capsule, 'Rattleweed', 'Rattle-baskets' and 'Rattle-pods' as well as 'Red Rattle' (Grigson 1955, 1987; Vickery 2019).
Grigson (1955, 1987) explains that in Germany, P. palustris and P. sylvatica were both referred to as 'Läusekraut', our 'Lousewort' being a direct translation, "bycause the cattell that pasture where plenty of this grasse groweth become full of lice" (Lyte 1578). The plants were supposed to give the cows the fluke-worms of liver-rot. Other plants that were reputed to give the animals the rot included Drosera rotundifolia (Round-leaved Sundew), Pinguicula vulgaris (Common Butterwort) and Hydrocotyle vulgaris (Marsh Pennywort), all plants of similar constantly damp or wet ground habitats. "The herbe is not onely unprofitable, but also hurtfull, and an infirmitie of the medowes.", according to Gerard (1597, 1633).
Threats
None in Fermanagh, at any rate, but subject to habitat loss through drainage and management neglect of wet ground in many areas elsewhere.