Crepis capillaris (L.) Wallr., Smooth Hawk's-beard

Account Summary

Growth form and preferred habitats

C. capillaris is a very variable, semi-rosette winter or summer-annual therophyte that relies entirely on seed for its reproduction and for its overwintering survival. However, under less favourable growing conditions, it takes longer for the plant individual to achieve the threshold flowering size and the plant then behaves as a biennial, overwintering as a leaf rosette with flowering delayed until its second year of growth. Grime et al. (1988, 2007) noted that some populations in the Nottingham area also contained polycarpic perennial individuals (ie long-lived forms capable of repeat flowering and fruiting in successive years).

As the common name 'Smooth Hawk's-beard' suggests, C. capillaris is an almost hairless plant. It generally produces several more or less wiry stems arising from the basal leaf rosette, but it can develop a solitary more robust stem and produce larger than average flowerheads, densely clothed with blackish glandular hairs. This latter form of the plant is referred to as var. glandulosa (Silverside 1990).

The long, narrow, sharply lobed, pinnatifid leaves and the small flowerheads (1-1.5 cm in diameter) make it quite easy to identify, although the basal rosette and lower stem-leaves are, in fact, very variable in form. In outline, they are linear-oblong to lanceolate and shaped like a lyre (ie with a much larger terminal lobe), or else they are pinnate with the lobes pointing backwards, or they may simply be toothed. Leaf variability extends to their surfaces, which may be smooth or sparsely hairy on one or both surfaces.

C. capillaris is a common plant of dry or damp soils in a wide variety of mainly lowland habitats that contain patches of bare soil, or which are subject to either sufficient disturbance or recurring drought conditions to keep them open to seed-borne colonising species (Grime et al. 1988, 2007). In Fermanagh, it is chiefly found on warm, sunny, open roadside verges, but it also occurs in meadows, waste ground, on walls and in quarries. C. capillaris is essentially an early-colonising ruderal, with a degree of stress tolerance that includes adaptation to infertile, unproductive growing conditions and transient populations involving rapid germination and expansion, and equally rapid turnover when the habitat changes. Although it can survive moderate grazing and trampling, it is considered a poor competitor in closed-turf vegetation, except occasionally on sandy soils or on lawns (Sinker et al. 1985; Grime et al. 1988, 2007). C. capillaris is absent from wetland, woodlands and from strongly acid soils with a pH below 4.5.

The established strategy of C. capillaris is categorised as R/SR, meaning it is intermediate between a straightforward Ruderal and a Stress-tolerant Ruderal (Grime et al. 1988, 2007).

Flowering reproduction

C. capillaris flowers in June and July – although some plants, including some damaged earlier in the season, may produce a second flush of flowering in August and September. The small flowerheads, only 1.0-1.5 cm in diameter, each contain around 40 strap-shaped (ligulate), yellow florets. An average plant bears ten heads which are insect pollinated (usually by bees and flies) and are self-incompatible. Seed is set later than most other winter annuals, from July onwards. It is wind-dispersed and has only a limited capacity for persistence at or near the soil surface (Grime et al. 1988, 2007; Roberts 1986) thus suggesting it probably does not form a significant seed bank. The survey of soil seed banks in NW Europe contains a total of ten estimates of seed longevity. As usual, the estimates vary, the count in this case being, transient (ie up to one year) five; short-term persistent (ie less than five years) one; more than five years, one; present in soil, but survival undetermined, three (Thompson et al. 1997).

Typically the seed germinates in the autumn after its production and dispersal. The seedling produces a taproot and overwinters as a rosette of leaves.

Interestingly the species has only six chromosomes in the diploid, one of the lowest counts for any common plant in B & I, a property possibly enabling it to evolve more rapidly than other plants (Stebbins 1974).

Fermanagh occurrence

In Fermanagh, C. capillaris is only frequent in the lowlands, but has been recorded in 110 tetrads, 20.8% of the VC total. Only 98 tetrads, however, have post-1975 records. As Hackney et al. (1992) determined for the FNEI 3, almost certainly all the Fermanagh plants should be regarded as var. glandulosa, but varieties have not been distinguished during the field recording for The Flora of County Fermanagh.

British & Irish occurrence

Common and widespread throughout most of B & I (although not in Fermanagh), this wintergreen annual or biennial is by far the most common and widespread Crepis species, occurring in every VC in B & I. The New Atlas hectad distribution map shows that its presence thins noticeably towards the N & W in Britain, becoming rare or scarce in N Scotland, undoubtedly a reflection of soil acidity and higher altitude in these regions. In Ireland, the distribution at the hectad level of discrimination shows C. capillaris also declining towards the W of the island for similar reasons (altitude and acidity) (Preston et al. 2002). Interestingly, the equivalent map in the Atlas 2020 displays a more total hectad presence of C. capillaris across the whole of both B & I, with the notable exception of the highest altitudes in the Scottish Highlands. The increased coverage displayed in this comparison undoubtedly reflects the very intensive recording effort made by BSBI members in the 2020 flora survey in both B & I. The Change maps associated with the several BSBI surveys indicate there have been both gains and losses in populations across the N of Britain, especially on higher ground and a similar picture emerges from the data in midland and western parts of Ireland (F.H. Perring and K.J. Walker, in: BSBI Online Plant Atlas 2020, https://plantatlas2020.org/atlas/2cd4p9h.rx, accessed 5 July 2023).

Fossil history

Fossil evidence of C. capillaris did not appear in Britain until late in the current Flandrian interglacial, stage VIIb, which equates with the Late Bronze Age (at a site at Minnis Bay). However, Godwin (1975) points out that another fossil record exists from the previous Weichselian glacial period. It thus appears very possible, or indeed probable, that the species really represents another archaeophyte weed, probably accidently or incidentally introduced by man and his activities, even if this pre-dates agriculture.

European and world occurrence

The species is fairly common and widespread in W, C and S Europe, including in disjunct southern parts of Scandinavia and very rare and scattered eastwards into W Russia. To the south, it becomes scarce and perhaps adventive on the northern shore of the Mediterranean, although it does reach S Greece (Fitter 1978; Hultén & Fries 1986, Map 1930). It is an introduced weed in N & S America, S Australia and New Zealand and probably likewise in the Azores and the Canary Isles (Hultén & Fries 1986, Map 1930).

Names

The name 'Crepis' is derived from the Greek 'krepis', which was applied by the ancient Greek 'Father of medicine', Theophrastus, to the present day Picris echioides (Bristly Oxtongue) (Gilbert-Carter 1964). More work is required on the subject of identifying modern plant species from ancient Greek and Latin texts, a fact to which John Raven drew attention in his 1976 Gray Lectures in Cambridge (Raven 2000). It is important to be wary of over-simplification of the problems of such long-distance, long-duration plant identifications. The Latin specific epithet 'capillaris' is Latin for 'fine as hair', but it is not clear to what aspect of the species this refers.

The common name 'Hawk's-beard' was invented, according to Prior (1879), by S.F. Gray, "and assigned, without any reason given, to the genus Crepis L.". One could speculate that since Crepis is so close to Hieracium, common name 'Hawkweed', that Gray chose to create a similar common name, based on the ancient legend or belief described by Pliny, whereby, "hawks tear the plant apart and wet their eyes with the juice, so dispelling dimness of sight, when it comes on them" (Grigson 1974).

Threats

None.

References

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