Gentianella campestris (L.) Börner, Field Gentian

Account Summary

Growth form and preferred habitats

This little, erect, branching annual or biennial gentian is nothing like as conspicuous as Gentiana verna (Spring Gentian), or other members of the family found in the European mountains possessing unforgettable brilliant blue corollas. The flowers in this instance are a rather dark bluish-purple, the tube with a long bluish fringe at the mouth, the corolla then dividing into four, occasionally five, ± spreading petal lobes. The calyx is undoubtedly the most distinguishing feature of this particular species, having four lobes, the two outer ones being much wider, enveloping the other pair.

When not in flower, Field Gentian is very inconspicuous and difficult to locate and, consequently, must often be overlooked. G. campestris flowers from early July to late September and appears rarely and very sparingly in short, grazed turf in dry, rocky, heathy unimproved grassland in a variety of terrain, from lowland pastures to cliffs, screes, to mountain (or rather hilltop) pastures. It frequents mildly acidic to neutral, infertile soils in a variety of open habitats, often over leached limestone, or elsewhere on fixed maritime sand dunes. It is generally a lowland species in B & I, but does reach an altitude of 915 m at Cairnwell, NE Scotland (VCs 89 & 92) (R.D. Porley, in: Preston et al. 2002; Smith & Lockwood 2011; Stroh et al. 2019). It prefers constantly moist, well-drained soils and full sunlight and it is slightly salt-tolerant (Hill et al. 2004).

Locally in Fermanagh, these dry, rocky grassland habitats are confined to the limestone areas of the county where the shallow soils are heavily leached, nutrient-depleted and become neutral or mildly acidic, so that a species-rich pasture of low productivity develops and persists. G. campestris is often found on the shallowest soils around rock outcrops on cliffs, screes and limestone pavement. Typical associated species include Antennaria dioica (Mountain Everlasting), Briza media (Quaking-grass), Campanula rotundifolia (Harebell), Danthonia decumbens (Heath-grass), Galium verum (Lady's Bedstraw), Linum catharticum (Fairy Flax) and Thymus polytrichus (Wild Thyme).

Flowering reproduction

Regeneration is entirely by seed and the species is monocarpic. Germination takes place in the spring, dormancy being overcome by cold stratification overwinter (Milberg 1994). The low-growing, erect flowers are visited by long-tongued humble-bees and butterflies, the only insects in B & I that are able to reach into the fringed corolla tube to find the nectar legitimately, although as in the genus Gentiana, robber bumble-bees may bite and bore holes through the calyx and corolla tubes and steal the food reward. The flowers also self-pollinate very readily and full seed set often results (Clapham et al. 1962; Lennartsson et al. 2000). Measurements made of reproductive capacity by Salisbury (1942) found G. campestris plants produced an average of just 5.5 capsules, with an average seed content of 60, giving a calculated mean output of 325 ± 23 seeds per flowering plant. Subsequent study found fruits contained between 40 and 120 ovules, supporting Salisbury's findings (K. Walker, in: Stroh et al. 2019).

Seed has proved nigh impossible to germinate experimentally, which probably indicates a long period of seed dormancy, a feature that is also the case in G. amarella (Autumn Gentian) (Pritchard 1959). Dispersal of the small, lightweight seed from the fruit capsule is most probably achieved by wind, especially during the winter when the surrounding vegetation dies down somewhat.

Horses, cattle and undoubtedly other wild grazing animals, eat the fruiting plants and disperse gentian seed with their dung, despite the fact that all Gentian species contain bitter glycoside substances akin to tannins. As a result of these, the species had herbal medicinal uses in the past (Ridley 1930; Grieve 1931).

There is no evidence for G. campestris having long-term survival of buried seed. The soil seed bank survey of NW Europe did not mention G. campestris, but of 18 reports for eight related Gentiana and Gentianella species, only one told of seed surviving longer than 3 years (ie short-term persistent) for Gentianella germanica (Chiltern Gentian) (Thompson et al. 1997). The seed must therefore normally be transient, surviving for one year or less.

The observation that in Britain undergrazing represents a greater threat to G. campestris populations than overgrazing, suggests the species cannot survive or 'out-live' unfavourable growing conditions when they occur, since it has no buried seed reserves available to revive and re-establish the population should favourable conditions return. Undergrazing or neglect of grassland quickly leads to invasion and overgrowth by shrubs, vigorous herbs and coarse grass species (Walker et al. 2017; K. Walker, in: Stroh et al. 2019).

Fermanagh occurrence

In Fermanagh, there are records of small populations of G. campestris from just nine post-1975 tetrads, plus one tetrad with a 1970 date at Oweyglass upland. As the tetrad distribution map clearly demonstrates, its Fermanagh sites fall into two distinct districts, around the Monawilkin-Knockmore-Legland area and S of Lower Lough Macnean in the limestone uplands around the Crossmurrin NR and the Gortmaconnell Rock area.

Irish occurrence

In NI, G. campestris to some extent mimics (without actually belonging to) the group of so-called Irish 'Mountain plants', a listing similar to and based upon Watson's 'Highland Type' (Watson 1859). This grouping was very loosely defined by Watson as, "plants chiefly seen about the mountains" (Praeger & Megaw 1938). The definition does NOT carry the inference that 'mountain plants' are confined to upland sites, and in Ireland (especially as one travels westwards), many of these mountain species also occur in utterly different growing conditions. For instance, some of them grow right down to sea-level in coastal, often sandy habitats, including Dryas octopetala (Mountain Avens) and Gentiana verna (Spring Gentian) in the Burren and Connemara (H9 & H17) (Moore & More 1866; Colgan & Scully 1898; Praeger 1934; Webb & Scannell 1983).

In parallel with this so-called 'mountain group' of Irish plants, G. campestris occurs and, indeed, is much more frequent and prevalent in coastal sites in the N & W of Ireland, while also being found down the E coast as far south as Wexford (H12). However, G. campestris is also found growing at high elevation in the Wicklow hills (H20) (Perring & Walters 1962, 1976; Hackney et al. 1992).

G. campestris populations have been in steady decline in NI over the last 60 years or more, and NIEA has listed it as a priority species of conservation concern. In NI, the number of hectads with records of any date total 36, but only 13 squares have post-1986 observations (NI Vascular Plant Database, accessed 2010).

British occurrence

Previously widespread in Britain, G. campestris is now rare and localised in S England and S Wales, but still relatively frequent in the Pennines, Scottish mountains and around the Scottish coast and islands (Smith & Lockwood 2011). However, the species has suffered a severe decline across its whole European range since about 1930 and some lowland regions have lost the majority of their populations in the last 50 years (K. Walker, in: Stroh et al. 2019). This has also been the experience in B & I.

In England and Wales, the decline of the species is very marked, especially in SE England (Walker 2007). It is now extremely rare in southern England, except in the New Forest (VC 11), where populations are stable or possibly expanding. Cumbria (VCs 69 & 70) remains the last major English stronghold – although even here it has disappeared from over half of the hectads for which there are post-1930 records (Halliday 1997; Preston et al. 2002).

Possible explanations for species decline

G. campestris and the closely related Autumn Gentian (G. amarella) both require an open, short turf habitat. The demise of much of the rabbit population following myxomatosis in the 1950s undoubtedly affected the extent of open grassland habitats suitable for both these Gentianella species (Pritchard 1959). This detrimental situation has not yet been reversed by the development of alternative grazing practices. Surveys and monitoring of surviving populations by government conservation bodies and subsequent listing in Red Data Book terms as 'Vulnerable' or 'Endangered' species of concern (Cheffings & Farrell 2005), together with listing of sites of special scientific interest, should certainly have helped alleviate environmental pressures to some extent. However, active management measures, including reintroduction programs and the careful addition of monitored low-intensity, autumn to spring grazing by sheep and rabbits, may also be required in the long term to replace or restore extinct or near-extinct populations (Smith & Lockwood 2011).

The widespread decline of G. campestris and G. amarella populations in B & I is probably associated with the loss of hay-meadows (including their conversion to silage) and, in less steep or hilly areas, agricultural pasture 'improvement' measures, involving ploughing, reseeding and the regular application of fertiliser (often as slurry). Together with the widespread use of herbicides, farmland management practices such as these have increased grass production and threatened the survival of these two interesting Gentianella species.

Populations of G. campestris are still being lost in Britain due to overgrazing in the uplands and the neglect or mis-management of lowland pastures. Cessation or a marked reduction in grazing or mowing of grassland, especially in more fertile mesic sites, can quickly result in local extinction of G. campestris (Stroh et al. 2019).

European occurrence

A European endemic species, G. campestris has a boreo-temperate phytogeographic distribution, but is declining in presence throughout its range (Preston & Hill 1997; Smith & Lockwood 2011). It is widespread across N Europe, including Iceland and extends southwards to the Alps and more rarely to the Pyrenees, Picos de Europa and Apennines (Hultén & Fries 1986, Map 1504; Smith & Lockwood 2011).

Uses

In herbal medicine, G. campestris fulfilled a similar role to Centaurium erythraea (Common Century) in acting as a replacement for the continental Gentiana lutea (Yellow Gentian) root. As such, it was used (especially in the north of England and in Scotland, where it was more frequent) as a tonic and for treating gravel, digestive complaints, and as a cure for jaundice (Allen & Hatfield 2004). In the Scottish Highlands, Field Gentian was used to treat a rickets-like disease in cattle that enforced crouching. Nowadays, this is recognised as a phosphorus deficiency (Vickery 2019).

Names

The genus name, 'Gentianella', is a diminutive of 'Gentian', which is a name in Pliny of a plant called after Gentius, a 2nd century Illyrian king, who is reputed to have discovered the medicinal use of Gentiana lutea (Yellow Gentian) (Gilbert-Carter 1964; Hyam & Pankhurst 1995). The specific Latin epithet 'campestris' means 'of the pasture' or 'from flat land' (Gledhill 1985).

Threats

Despite conservation listing and management measures over at least a decade, G. campestris populations remain small and declining. Most likely this is due to changes in land management and intensification of farming involving reseeding of old pastures, overgrazing of upland pastures and the use of fertiliser which encourages growth of stronger competitors. Atmospheric pollution and climate change may also be significant, but little information of these factors exists yet (K. Walker, in: Stroh et al. 2019).

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