Crepis biennis L., Rough Hawk's-beard

Account Summary

Growth form and preferred habitats

C. biennis is a wintergreen annual or biennial, stems and leaves usually covered with short, stiff, scabrid, white hairs – hence the common name, 'Rough Hawk's-beard'. However, it is important to realise that occasionally plants can be almost hairless. Typically, it grows up to 120 cm tall, which helps differentiate it from another related alien, C. vesicaria (Beaked Hawk's-beard), which small, poorly grown specimens of C. biennis very closely resemble (Silverside 1990). The resemblance between these two species in the past led to long-standing identification difficulties, records of C. biennis having frequently arisen through confusion with C. vesicaria (Watson 1883). Fruiting plants are readily distinguished, however, since achenes of C. biennis lack the long beak of those characteristic of C. vesicaria. The presence of white, silky hairs on the inner surface of the inner involucral bracts around the flowerhead further distinguishes C. biennis from aberrant forms of C. capillaris (Smooth Hawk's-beard). The outer involucral bracts are ± spreading and the bases of the stem leaves, while ± clasping the stem, lack the reflexed points found in both C. vesicaria and C. capillaris (Webb et al. 1996; Silverside 1990).

C. biennis usually occurs very locally in rough, dry grass by roadsides and waste places, or in moist, sunny meadows on moderately acid to neutral soils. It can sometimes occur in considerable quantity, especially where it most commonly occurs on chalk and limestone in the southern part of Britain, below a line between the Severn and The Wash (Sinker et al. 1985; Silverside 1990). The habitat and general appearance of the species is very similar to that of Sonchus arvensis (Perennial Sowthistle), but C. biennis flowers a little bit earlier in the year, in June and July (as opposed to July to September) and it has somewhat smaller flowerheads (S. arvensis heads are 3.5-4.0 cm in diameter).

Flowering reproduction

Rough Hawk's-beard flowers in June and July, producing corymbs of flowerheads 2.0-3.5 cm in diameter terminating the main stem and branches. The golden yellow flowers are pollinated by bees and hoverflies, but it may also produce seed asexually by apomixis, as commonly occurs in the related genera Hieracium and Taraxacum (Clapham et al. 1962, 1987).

Irish occurrence

Crepis biennis has long been recognised by most, but not all, Irish botanists as an established alien, first recorded in Ireland in the Baldoyle and Portmarnock area N of Dublin (Mackay 1825). Most probably, it was unintentionally introduced with agricultural seed or with soil on the roots of imported plant material (Botanist in Ireland, paragraph 72). Webb's Flora 6th edition (Webb 1977) unequivocally labelled it an alien introduction, and Webb & Scannell's (1983) Flora of the Burren & Connemara also described C. biennis as an alien, as did Bunker (1950) in his Flora of County Wicklow. However, for some unknown reason (perhaps a typographical oversight), the 2nd edition of the Census Catalogue of the Flora of Ireland failed to follow Webb's lead (Scannell & Synnott (1987). In her excellent Catalogue of Alien plants in Ireland, Reynolds (2002) noted the Cen Cat Fl Ir 2 failure to indicate alien status for C. biennis, but while listing sources back to Cybele Hibernica (1898) that did consider it alien, she did not treat it so, neglecting to supply further details of the species in her very relevant book. Nevertheless, in her subsequent Flora of County Limerick (Reynolds 2013) C. biennis was accepted as being an alien species.

In the latter decades of the 19th century, C. biennis began to spread northwards along railway embankments and roadside verges, a movement undoubtedly enhanced as speedier methods of mechanical transport developed across B & I. The species was first recorded in NE Ireland in 1880 by S.A. Stewart, but in the FNEI 2, Praeger was still reporting the plant as very local and it was not until 1939 that he first found the plant in Fermanagh (Praeger 1939).

In Ireland overall, this species is somewhat more a plant of the east of the country, eg FNEI 3 describes it as, "locally abundant". It is believed to be still increasing along roadsides in Cos Down (H38) and Antrim (H39).

Fermanagh occurrence

The Fermanagh Flora Database now contains records from 31 tetrads (5.9%) and, as the local distribution map indicates, they lie mainly in the S of the VC. C. biennis also appears to be spreading along roadsides, especially along the Enniskillen to Belturbet road. Interestingly, only one recent site in Fermanagh is in a meadow (just to the S of Clonatty Bridge, 1991, RHN).

British occurrence

In Britain, C. biennis is a rather local plant species of rough grassland on chalk and limestone. It is regarded by some botanists as 'probably native' on chalk soils in SE England (eg Clapham et al. 1987), although the argument and evidence to support this contention has not been uncovered by the current author (RSF). C. biennis has been known in England since 1688 when the competent and well-travelled botanist, James Newton, reported it to John Ray (Clarke 1900; Pearman 2017). However, this early record of itself does not provide evidence of native status, since the plant could still have arisen as a neophyte introduction. Beyond the limited, but quite large area of southern England already mentioned and mapped in the New Atlas, C. biennis occurs as a frequent to scarce introduction in Britain, stretching northwards to C Scotland (Silverside 1990; Stace 1997). It has very probably been spread with agricultural grass seed mixtures and occasionally it manages to persist locally in pastures, field margins, roadside verges, dry banks and waste ground. In N & W Britain at least, C. biennis more often behaves as a casual species, appearing and disappearing in sporadic, transient populations around the country.

European occurrence

A European temperate species, C. biennis is found across most of Europe, except on the N, S and E margins of the continent. It stretches from the centre of Spain eastwards into W Russia and northwards in the Baltic region. To the south, it has been recorded in Sardinia and well down into S Italy on the western side of the peninsula, the N Balkans and W Turkey. Since it is frequently introduced with grass-seed, it is doubtfully native in many regions, especially towards the north of its mapped distribution (Tutin et al. 1976; Hultén & Fries 1986, Map 1929).

Threats

None.

References

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