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Campanula rotundifolia L., Harebell

Account Summary

Native, local, frequent to occasional. Circumpolar boreo-temperate.

1881; Stewart, S.A.; Co Fermanagh.

March to December.

Growth form and preferred habitats

This polycarpic, semi-rosette, wintergreen perennial has a slightly creeping, slender, much branched rootstock or rhizome that produces adventitious buds. C. rotundifolia produces erect, wiry stems 15-50 cm tall, simple or branched, leafy to half-way, often from a decumbent base. Basal leaves are rounded or heart-shaped, crenate, on petioles up to 6.0 cm, some (but not many), may be present at anthesis (flowering time) which is from July to September. The stems are "sparsely leaf up to the inflorescence" (M. Kovanda, in Tutin et al. 1976). Leaves on the decumbent part of stem, if it exists, have petiole stalks and are lanceolate, their margins entire or serrately toothed and apex acute (Clapham et al. 1987). Lower stem leaves are alternate, lanceolate; middle and upper leaves tend to be are narrow, almost linear, margins ± entire, 15-25(35) × 0.7-1.5 (3.0) mm, narrowed to a sessile base (Sell & Murrell 2006; Poland & Clement 2009).

C. rotundifolia competes best on shallow, dry or well-drained soils, as on cliff rock ledges and short, dry, sometimes rocky, unproductive grassland, including sheep-grazed pastures, sandhills, heaths and rocky hill screes and summit areas, as well as open scrub, quarry and other spoil-heaps, railway ballast and wayside verges (Sinker et al. 1985; Grime et al. 1988, 2007). On account of its mountain habitats, it can be found at altitudes of up to 1160 m (in the Breadalbanes in Mid Perthshire (VC 88)). It appears to be limited to infertile, relatively unproductive habitats subject to little in the way of disturbance, being absent from heavily disturbed and fertile environments. It can tolerate a wide range of soil types and pH range, occupying both mildly acidic and calcareous substrates, and lead-spoil heaps where heavy-metal tolerant races are known to occur (T.D. Dines, in: Preston et al. 2002). It increases in frequency and abundance as soil pH rises, and is completely absent from wetlands and strongly acidic conditions. It usually appears as a minor component of grassy and rocky unproductive vegetation occupying the lower levels of the canopy, thus demonstrating an at least moderate degree of shade tolerance (Grime et al. 1988, 2007). It prefers sunny, more exposed conditions, as met with on mountain cliff ledges, and is tolerant of grazing and trampling but not competition from vigorous grasses (Sinker et al. 1985).

The established strategy of Harebell is categorised as S/C-S-R, meaning it is intermediate between a Stress-tolerator and a plant with a more general balance of all three survival growth strategies, Competitor, Stress-tolerator and Ruderal (Grime et al. 1988, 2007; Parnell & Curtis 2012).

The species is not particularly aptly named since the round or oval shade-leaves are confined to the small, insignificant and sometimes difficult to locate basal rosette; many of those leaves are dead by the time the plant is in flower. The much more conspicuous sun-leaves borne on the erect flowering stems, are lanceolate on the lower stem and decidedly linear above.

The plant is extremely variable in size. In the vegetative, non-flowering state it is often very stunted, and although slow-growing, it manages to persist among quite dense, shading, taller turf grasses and herbs or in sufficiently open areas of scrubland. Erect flowering stems may be relatively robust and can reach up to 50 cm in height, curving up from a decumbent base, although they often lean over when they elongate (Webb et al. 1996; Stace 1991).

Flowering reproduction

Flowers, bisexual, pendulous, solitary or in a short raceme of around ten flowers. Individual flowers shortly stalked; calyx teeth five, very slender; corolla bell-shaped, pale to bright blue, 5-30 mm, lobed 1/4-1/3 way to base, the bells 10-20 mm in diameter. The flowers are protandrous, insect pollinated and self-compatible. Nectar is secreted at the base of the ovary, attracting insects such as hoverflies and bees that have a sufficiently long proboscis to reach it. It is, however, partially concealed by the enlarged bases of the stamen filaments.

The pollination mechanism is interesting and is referred to as 'the stylar brush mechanism', in which pollen is not transferred directly from the anthers to the visiting insects in the normal way. In the young flower bud, the five anthers closely surround the hairy tip of the central style onto which they shed their pollen before the flower opens. In the freshly opened flower, the slender filaments of the stamens have already shrivelled and the pollen sticking to the tip of the style is ready to be picked up on the hairy body of a bee, wasp or hoverfly crawling into the corolla bell. After a few days, the branches of the style diverge, exposing the three receptive stigma lobes which take up the position previously occupied by the pollen brush. Before the flower withers, the stigmas curve right back so far that they touch the remaining pollen, so that self-pollination may take place if insect visitors fail to pollinate the flower (Proctor & Yeo 1973; Hickey & King 1981).

Seed is set from August onwards. The sub-globose fruit capsule, 5.0 × 2.5 mm, remains pendulous and bears persistent withered remains of petals and sepals. It opens by three basal pores, the mouths of which are surrounded by valves. In wet weather, these valves swell up and close the pores again, but in dry conditions they are open and the seeds are shaken out and carried away by the wind, each fruit releasing 50 or more small, 0.2 mm, ovate, compressed, yellow seeds. In C. rotundifolia, the dehiscence continues as the seeds fall, so that eventually only the ribs of the capsule remain, allowing all the seeds to escape also at the sides (Ridley 1930, p. 19). Seeds have also been reported from horse droppings, so grazing stock animals may also assist dispersal by transporting the fruit capsules or seed internally in their alimentary canal (Ridley 1930, p. 360). In some habitats, including on walls, seeds have also been reported to be dispersed by ants (Segal 1969).

Seed is persistent in the soil, some estimates reckoning for up to five years (Thompson et al. 1997).

Vegetative reproduction

Plants growing in closed vegetation communities may also regenerate and persist using the creeping, horizontal rhizomes or runners the plant produces at the soil surface or within the bryophyte layer. These horizontal branches, below or above ground, spread out from established individual plants by means of adventitious rooting plantlets, gradually building clonal patches of the species (Grime et al. 1988, 2007).

Variation

This polymorphic species together with infraspecific taxa forms a difficult European complex of differing chromosome numbers, represented in B & I by both tetraploids and hexaploids. The New Flora of the BI (1991, 1997) suggests Irish plants belong to the hexaploid race which resembles the Scandinavian (but diploid) species, C. giesekiana auct., non Vest. This B & I form has recently been renamed subsp. montana (Syme) P.D. Sell (Sell & Murrell 2006); however, none of the Fermanagh C. rotundifolia records have been determined at subspecific level. Clearly more taxonomic work is required on Campanula, and from the current author's (RSF) experience of using Flora Europaea 4 to key out species in the Alps, Pyrenees and the Mediterranean, the same can also be said regarding parts of the continent!

Fermanagh occurrence

C. rotundifolia closely follows the distribution of limestone in Fermanagh and is commonly found around the shores of Lower Lough Erne and on limestone grassland and cliff ledges, including the wooded Cliffs of Magho (otherwise known as Pollaphuca or Poulaphouca) overlooking the Lower Lough. Apart from this latter situation, it avoids both woods and wetlands entirely, and it does not seem to invade disturbed or man-made habitats with us, such as waysides or walls, all its sites being much more natural or semi-natural.

The species has been recorded in 49 Fermanagh tetrads, 9.3% of the VC total. As the tetrad distribution map shows, it is almost entirely confined to the western half of the VC. The most isolated record plotted was found at Inishroosk Td, a mainland peninsula on the eastern shore of Upper Lough Erne (GR H310327) in July 1986 by L.W. Austin and P.J.T. Brain, two members of the EHS Habitat Survey Team.

Irish occurrence

Harebell has been recorded to some degree (at least once) in 30 of the 40 Irish VCs (Cen Cat Fl Ir 2). However, this small perennial is much more local in its occurrence than this might suggest and, indeed, it is only really frequent and locally abundant in parts of the N & W of the island and there are major areas of the S & E of the RoI where it is completely absent (Perring & Walters 1962, 1976; An Irish Flora 1996; New Atlas).

British occurrence

C. rotundifolia is very widespread across most of Britain from the south coast of England to Shetland, although there are surprising areas where it is absent or in major retreat. These areas include the Channel Isles, SW England, S Wales, the area south of the Wash and, in Scotland, up the W coast above Oban (T.D. Dines, in: Preston et al. 2002). It is not easy to explain some of these absences, but the species overall shows little or no evidence of decline from the distribution mapped in the earliest BSBI Atlas (Perring & Walters 1962).

Fossil record

Campanula pollen is not readily identified below genus level in the fossil record, but the seeds of C. rotundifolia are distinguished, although with difficulty and only one scientist (a Miss Bell) is credited with all the Middle Weichselian records in Godwin (1975). Seeds were also found in the Corton interstadial of the Anglian glacial stage and in the early Wolstonian. All C. rotundifolia pollen records in B & I are qualified; however, the fossil record does still indicate that the species was common in B & I during the last glacial stage, and probably was so in earlier ones too. Evidence for persistence through the current Flandrian interglacial (in Ireland, the 'Littletonian') is lacking, although this is likely the case (Godwin 1975).

European and world occurrence

Circumpolar boreo-temperate in phytogeographical terms, C. rotundifolia is a polymorphic species of some taxonomic complexity with differing races and subspecies across the northern boreo-temperate zone where it is almost continuously present. It is often referred to as an 'arctic-alpine' and occurs commonly throughout Scandinavia, even as far north as the North Cape and the Kola Peninsula. Broadly defined, it is widely distributed in Eurasia, although in Europe it is rare and scattered south of the Pyrenees and around the Mediterranean, but is present in both Sardinia and Algeria. Elsewhere, it is completely circumpolar (although with gaps, and therefore discontinuously so) and it is well represented in both Asia and N America (Porsild 1964; Godwin 1975; Hultén & Fries 1986, Map 1757).

Names

The genus name 'Campanula' is a Latin diminutive of 'campana', 'bell', thus translating as 'little bell', from the shape of the corolla (Gilbert-Carter 1964). The Latin specific epithet 'rotundifolia' translates as 'round-leaved'. The English common name 'Harebell' refers to the herbivore Hare, of which there are two species in Ireland, Lepus europaeus (Brown Hare) and L. timidus hibernicus (Mountain (or Irish) Hare) (Hayden & Harrington 2000).

The plant has many other alternative common names, Grigson (1955, 1987) listing an additional 28 of them and Vickery (2019) no less than 35. Thirteen of the names include the 'bell' word element and six refer to 'thimbles', another reference to the corolla shape. It also had fairy links such as 'Fairy Cap', 'Fairy Cup', 'Fairy Bells' and 'Fairy Ringers' and this and 'Old Man's Bell' (a reference to the devil), 'Witch Bells' and 'Witch Thimbles' were all subtle warnings not to pick the flowers for fear of bad luck (Grigson 1955, 1987).

Threats

None.

References

Scannell, M.J.P. and Synnott,D.M. (1987); Grime, J.P., Hodgson, J.G. and Hunt, R. (1988, 2007); Webb,D.A., Parnell,J. and Doogue,D. (1996); Perring, F.H. and Walters, S.M.(eds.) (1962, 1976); Preston et al. 2002; Godwin 1975; Hultén & Fries 1986; Grigson 1955, 1987; Porsild 1964; Hayden & Harrington 2000; Sell & Murrell 2006; Gilbert-Carter 1964; Thompson et al. 1997; Ridley 1930; Proctor & Yeo 1973; Hickey & King 1981; Parnell & Curtis 2012; Sinker et al. 1985; Vickery (2019); Tutin et al. 1976; Segal (1969); New Flora of the British Isles (1991, 1997); Poland & Clement 2009.