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Parentucellia viscosa (L.) Caruel, Yellow Bartsia

Account Summary

Native, very rare. Mediterranean-Atlantic.

25 August 1996; Northridge, R.H.; E of Rossmore Point, Lower Lough Erne, Castle Archdale estate.

Growth form and preferred habitats

An attractive, erect, rigid, usually unbranched, grey-green, annual root hemi-parasite with fibrous roots that parasitise grasses and other associated herbs. Up to 50 cm tall, P. viscosa, as its species name indicates, is clothed overall with downy, sticky (viscid), glandular hairs. It has oblong, toothed, stalkless leaves that can be opposite or alternate.

Scarce or rare as a native plant species in both B & I, Yellow Bartsia usually grows in lowland, damp, sunny, rough- or pasture grasslands, often on nutrient-poor, stony, sandy soils close to the sea. Sites are often along tracksides or in pasture grassland that is patchily grazed, ie subject to moderate levels of disturbance that help keep the short turf open, providing suitable vegetation gaps for germination and establishment of P. viscosa on host plants (Garrard & Streeter 1983; Perring & Walters 1989; French 2020). Fixed dune grassland in dryish, dune slacks is one of its characteristic habitats and poor, infertile pasture reclaimed from dampish heathland is another (M.C.F. Proctor, in: Stewart et al. 1994).

Flowering reproduction

Seeds germinate in the spring and, being an annual species, late-flowering, from June or July to October, P. viscosa reproduces entirely by seed. The inflorescence is a terminal spike-like raceme of flowers in the axils of leaf-like bracts. The large, yellow two-lipped flowers, 16-25 mm in length, 11-13 mm in diameter, have a long corolla tube (a little longer than the tubular calyx), the lower lip much longer than the upper hooded one (Perring & Walters 1989). The four stamens are included in the upper corolla lip. Pollination is carried out by Hymenoptera and Diptera (ie bees, butterflies and flies) (Fitter 1987).

The fruit is a hairy, narrow capsule, 7-9 mm, slightly longer than the calyx tube, and contains many small seeds, 0.4 × 0.3 mm, finely striate and brown in colour (Butcher 1961). There is no oil body on the seed, so ant-assisted dispersal does not occur in this species (Sell & Murrell 2007). The current author (RSF) has not been able to find basic information on such topics as seed number (apart from 'many small seeds') per capsule, mean number of flowers per plant, mode of seed release and dispersal, mean level of seed production, duration of survival in the soil seed bank and percentage germination. Clearly work is required to remedy this situation and any observations would be very welcome.

Fermanagh occurrence

P. viscosa is usually associated with damp, open sites on sandy, grassland that typically become flooded in winter, such as occurs for example in fixed coastal dunes or in other low-lying ground near the sea, so its discovery for the first time at Castle Archdale on the shore of Lower Lough Erne made by RHN in 1996 was quite remarkable. A second Fermanagh site emerged in 2001 when RHN and F. Carroll came across three individual plants growing in damp ground at Cross Townland, on the northern outskirts of Enniskillen town. In October 2004, RHN found a third site, again at Castle Archdale, where at least one plant occurred in an old reseeded lawn at the front of the remains of the major house of the estate.

British and Irish occurrence

In Britain, there has been some awareness in recent times that this species is in a phase of expansion from its previous known distribution, the plant being now observed colonising in both northern and eastern directions. Very probably, this is the result of recent introductions from imported wild flower seed mixtures (M.C. F. Proctor, in: Stewart et al. 1994; Webb et al. 1996).

Throughout B & I, the native distribution of P. viscosa is frequent to very local and is largely confined to the S & W of both islands, but with scattered occurrences further north in NW England, S Scotland and N Ireland. In England, it is mainly found from Kent to Cornwall and the Channel Islands, but it extends north to Dunbartonshire in W Scotland. The species is limited to lowland sites and is most often coastal, occasionally occurring in abundance (Garrard & Streeter 1983).

Taken together, this pattern strongly suggests the species is temperature limited, requiring both a mild winter and a following mild spring growing season. The native distribution is roughly bounded by the 5°C mean January isotherm, which fits with this notion of a temperature limit to distribution (M.C.F. Proctor, in: Stewart et al. 1994).

In Ireland, it occurs in SW, NW and Western regions. P. viscosa has its most northerly occurrence in Ireland on the shores of Lough Swilly in E Donegal (H34), but it is much more prevalent and frequent in the SW of Ireland and almost entirely absent from the C & E (BSBI Atlas 2). In the NE of Ireland, Harron (1986) found it around Lough Neagh in five sites over four VCs, and it also occurred at the coast near Ballykelly, Co. Londonderry (H40) (Hackney et al. 1992).

The New Atlas map displays a major species decline in SW Ireland, probably the result of re-seeding of older pastures. Elsewhere in Ireland, the distribution appears to be stable. In Britain and the Isle of Man, the New Atlas hectad map shows introduced plants are increasingly frequent and widely scattered from the S coast of England to near Inverness in Scotland (F.J. Rumsey, in: Preston et al. 2002).

European and world occurrence

P. viscosa belongs to the Mediterranean-Atlantic phytogeographical element and is widespread in S & W Europe, the Mediterranean basin, the Iberian Peninsula and W France. It is also found in Macaronesia, including N Africa and the Azores, and has its northern limit in W Europe near Lough Lomond in Scotland (M.C.F. Proctor, in: Stewart et al. 1994; Sell & Murrell 2007).

Names

The genus name 'Parentucellia' was given in memory of T. Parentucelli who was an important figure in the revival of learning and became Pope Nicholas V (1447-55). He founded the Vatican Library and the Botanic Gardens at Rome (Melderis & Bangerter 1955; Gilbert-Carter 1964). The previous genus name was 'Bartsia' and one of the English common names is 'Viscid Bartsia' (Butcher 1961). The genus name 'Bartsia' was given in memory of a Dutch physician, J. Bartsch (1709-38) (Melderis & Bangerter 1955; Gilbert-Carter 1964). The Latin specific epithet 'viscosa' means 'sticky' or 'viscid', literally 'full of bird-lime' ('viscum') (Gilbert-Carter 1964).

Threats

None.