Gentianella amarella (L.) Börner, Autumn Gentian

Account Summary

Growth form and preferred habitats

A very variable species, G. amarella is sometimes considered a summer annual, ie it germinates in the spring and produces a flowering individual later in the year. However, if insufficient photosynthetic resources are accumulated to permit reproduction in this manner, and in G. amarella this is usually the case, then the plant behaves as a biennial, producing an overwintering underground bud in the first autumn after germination and flowering in the second summer. The aerial leaf rosette dies away completely in the winter, but the plant will re-grow and flower during its second season (Pritchard 1959). G. amarella has calyx lobes all ± equal in size and a corolla that is usually 5-lobed. The plant varies greatly in size, from 3-30 cm tall, stems simple or branched from the base. The flowers are slightly smaller than those of G. campestris (Field Gentian), usually bluish-purple, though occasionally pale blue, pink or white.

G. amarella is a more definite calcicole than G. campestris, being closely associated with dry or well-drained, nutrient-poor, infertile, grazed, short-turf, calcareous or basic pastures, dry banks and sandy or gravelly places, including maritime grey sand dunes and dune slacks, coastal machair and limestone quarries. Sometimes it is also found on similar well-drained basic soils in roadside cuttings, quarries and spoil-heaps (Kelly 1984; R.D. Porley, In: Preston et al. 2002). It is a mostly lowland species, but does occur in NW England at up to 750 m in Westmorland (VC 69) (Pritchard 1959; Sinker et al. 1985; Sell & Murrell 2009; Parnell & Curtis 2012).

Variation

There is considerable genetic variation within G. amarella, eg the flowers can be four- or five-parted, even on the same plant. Petal colour can range from the usual rather dull, dark purple to a much rarer white, pink or pale blue (Clapham et al. 1987; New Flora of the BI 1997). As a result, several local endemic subspecies have been described for B & I (Pritchard 1959).

Measurements of seven plant characters in Irish G. amarella plants made by Pritchard found they formed a homogenous group that lay outside the range of British and European material examined. The Irish plants differed in the size of their corollas and this was correlated with other small but definite differences. All Irish G. amarella plants are now assigned to the endemic subsp. hibernica N.M. Pritch., having slightly longer corollas and narrower and less tapering leaves than subsp. amarelle, to which it most closely lay (New Flora of the BI 1997; Sell & Murrell 2009).

However, Pritchard subsequently reconsidered the Irish material and decided to reassess its taxonomic rank, referring it then to "a race of G. amarella". Examination now confirms that the differences between Irish and British material are relatively small, and the separate subsp. hibernica is not worth retaining (Parnell & Curtis 2012). Stace (2019) continues to key out subsp. hibernica, but does admit it is, "possibly not worth separation from subsp. amarella". There currently are four subspecies recognised in B & I, subsp. amarella, subsp. septentrionalis, subsp. anglia and subsp. occidentalis, of which only the first is known to occur in Ireland (Stace 2019).

Hybrids

Rare hybrids are formed in Britain with three other Gentianella species, G. germanica (Chiltern Gentian), G. anglica and G. uliginosa, but none of these three species occurs in Ireland and naturally the hybrids are also absent (Stace et al. 2015). Two of the three 'species' (G. anglica and G. uliginosa), have been reclassified as subspecies (Stace 2019).

Fermanagh occurrence

The two or three Fermanagh stations for G. amarella are the only ones known in NI and thus RHN and the current author (RSF) believe it should be given the conservation status and protection of the Wildlife (NI) Order, Schedule 8. The sites are on limestone pastures at Screenagh (August 1970, L. Farrell, not refound), at Rahallan Td, S of Belmore Mountain (where patches can vary from a few plants to 400, 16 September 1990 to 4 October 2003, RHN), and on the SE and NE shores of Monawilkin Lough (where it occurs on up to 20 south-facing slopes, with total populations numbering up to thousands, September 1991 to September 2003, RHN).

G. amarella is rarer and more definitely lime-tolerant or calcicole than the closely related G. campestris (Field Gentian). However, both species occur in very similar shallow, leached, heavily grazed, species-rich, heathy limestone grassland situations. The two species overlap considerably in terms of their biology and ecology and sometimes they occur in mixed populations. To date, they have only been found together at five subsites in Fermanagh, around Monawilkin Lough on 13 September 2009. On 28 September 1991, thousands of G. amarella plants were observed on the SE slopes of Monawilkin, while in September 2009 the total number on all slopes around the lake was just 85 plants (RHN & HJN).

At the Rahallan site on Belmore, G. amarella is accompanied by Neotinea maculata (Dense-flowered Orchid), another extremely rare species in NI. Other typical lime-tolerant species which regularly associate with G. amarella include Ophioglossum vulgatum (Adder's-tongue), Arabis hirsuta (Hairy Rock-cress) and several further orchids, for example, Listera ovata (Common Twayblade), Gymnadenia conopsea (Chalk Fragrant-orchid), Plantanthera bifolia (Lesser Butterfly-orchid) and Orchis mascula (Early-purple Orchid).

Flowering reproduction

G. amarella is completely dependent on seed reproduction for increase, dispersal and overwintering survival. The throat of the tubular flowers opens and closes with surprising speed, depending on changes in temperature. Within 20 seconds of clouds rolling away and the sun emerging, the flower may open (Lousley 1969). They are said to be pollinated by bumble-bees, which are sufficiently strong and able to reach beyond the fringe of stiff hairs guarding the mouth of the corolla (Clapham et al. 1987). Soon after fruiting the plants die (Pritchard 1959). Measurements of reproductive capacity made by Salisbury (1942) found the seed output was between 800 and 900 per plant. The seeds are small and, in common with other members of the family, require a mycorrhizal partner in order to germinate.

Field observations show that G. amarella populations are sporadic, varying in numbers and location and this, together with experimental attempts to germinate seed, suggests a long period of seed dormancy exists (Pritchard 1959). An example of population fluctuation in Fermanagh was observed at Rahallen, where in 1996 Ian Rippey found 'a few', while in 2003, after a good warm summer, Robert and Hannah Northridge estimated 2,000 plants at the same site.

As in G. campestris, 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, rabbits and undoubtedly other wild grazing animals, eat the fruiting plants and disperse gentian seed with their dung (Ridley 1930).

The loss of rabbit populations since the 1950s is one feature that has destroyed previously suitable sites that supported Gentianella species on downs and dunes across B & I. This is largely due to the subsequent invasion of herb-rich grass heath by species such as Arrhenatherum elatius (False Oat-grass) and Brachypodium pinnatum (Tor Grass). Tall perennial grasses such as these rapidly oust gentians that are both short in stature and short-lived, and that need to seed every year in order to survive. Gentians are not ecologically flexible, and have suffered local extinctions in many sites as a result (Pritchard 1972).

Toxicity and herbivory

The presence of somewhat toxic bitter glycoside substances in the plant tissues does not greatly deter grazing animals (Ridley 1930). Previous to their decline from myxomatosis, rabbits frequently nibbled young gentian shoots to ground level, which would then react by re-growing into small, very bushy, tufted plants (Lousley 1969).

British and Irish occurrence

G. amarella remains widespread across lowland Britain in suitable basic and calcareous soil conditions. It reaches its highest altitude of 750 m at Knock Fell in Westmorland (VC 69) and is much more coastal in distribution in Wales and Scotland than is the case in England (R.D. Porley, in: Preston et al. 2002). In Ireland, Autumn Gentian is less frequent and more thinly scattered than in most of England, at least. It stretches across country from Co Dublin to Cos Galway and Clare and then northwards from there to Sligo, W Donegal and Fermanagh in a very disjunct manner (New Atlas). The Irish Census Catalogue lists the species as having been recorded at least once from 31 of the 40 VCs (Scannell & Synnott 1987), but, as is also the case in Britain, there have been numerous population extinctions due to changes in land management in the last 50 or more years, so that this no longer accurately summarises the present distribution.

European and world occurrence

The species s.l. is widely distributed in Eurasia and N America and is considered circumpolar boreo-temperate in its phytogeographic distribution. Subsp. amarella occurs across N & C Europe to E Ukraine, the Caucasus and the Yenisei region and W & C Siberia, but is scarce and very disjunct in S Europe and, apart from SE France, completely absent in the Mediterranean region (Hultén & Fries 1986, Map 1505; Clapham et al. 1987).

Uses

Like related members of the Gentianaceae, G. amarella has been substituted in B & I at times for the more famous Yellow Gentian (Gentiana lutea) in herbal medicine as a tonic, to cleanse the blood and kidneys, and for indigestion and colic, jaundice, wounds, sores and rheumatism (Grieve 1931; Grigson 1955, 1987; Darwin 1996).

Names

The 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 species name 'amarella' is the feminine diminutive of the Latin 'amarus', meaning 'bitter' (Gilbert-Carter 1964).

The English common name 'Felwort' originally referred to the important imported medicinal herb, Gentiana lutea, but the name became transferred to the related native herb with similar medicinal properties. The name is derived from the Old English or Anglo-Saxon 'feldwyrt', meaning 'field plant' or 'field-wort'. There may possibly have been a mistaken connection of the Old English or Anglo-Saxon 'feld', with the Latin, 'fel', meaning, 'gall', referring to the bitter taste of the plant (Prior 1879; Grigson 1955, 1987; Grigson 1974). In Shetland, G. amarella has the interesting and unusual name 'Dead Man's Mittens', because the half-open flower buds are likened to livid finger-nails protruding from the turf (Grigson 1955, 1987).

Threats

Rarity is always a threat to long term survival and this species requires statutory protection and active monitoring in NI.

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