Geranium dissectum L., Cut-leaved Crane's-bill

Account Summary

Growth form and preferred habitats

This species is distinctive and, when flowering, quite unmistakable; it is 10-60 cm tall, straggling, tap-rooted, with sub-rounded to kidney-shaped (reniform) leaves, lobed almost to the base and small flowers with bright purple petals 4.5-6.0 mm, notched at the tip (Sell & Murrell 2009; Parnell & Curtis 2012). A usually overwintering biennial or annual of disturbed lowland, it is found in sunny to semi-shaded sites, on moderately moist, fertile, calcareous to weakly acidic soils. The 1987-2004 Change in the British Flora monitoring survey found that it can survive competition and increase and thrive in arable crops, even if field nitrogen levels are high (Braithwaite et al. 2006). The same survey found evidence of a slight expansion of its range in the north, the areas involved suggesting that set-aside ground may have been partially responsible for the increase. G. dissectum is decidedly weedy in its ecology, its established strategy being categorised as R/CR by Grime et al. (1988, 2007), meaning it is intermediate between Ruderal and Competitive Ruderal. The Change survey gives good examples of this in action across Britain (Braithwaite et al. 2006).

Typical habitats of G. dissectum include grasslands (frequently in rather disturbed areas, like around gateways), hedgebanks, wayside grass, stony waste ground and in old quarries, but it is also frequent as a weed of arable cultivation, including winter wheat fields and garden situations. It continues to be introduced with temporary grass leys or clover crops as a seed impurity. A study of the weed flora of southern England between 1960 and 1997 suggested that Cut-leaved Crane's-bill was increasing in frequency (Marshall et al. 2003). In grassland grazed by horses, Cut-leaved Crane’s-bill is often associated with latrine areas (Gibson 1997). The grasslands it occupies in Fermanagh include riverbanks, lakeshores and parkland.

Flowering reproduction

From May to August, the plant produces tightly clustered cymose inflorescences of usually deep pink or bright purplish flowers, each with petals slightly notched and shorter than the hairy sepals. The rather small flowers mature in pairs, but even so they generally appear on the plant only a few at a time so that the species is quite inconspicuous and far from 'garden worthy'. Although the flower is reported to be protogynous (Hutchinson 1972), and is also said to attract at least saw-flies (Proctor & Yeo 1973, p. 134), in common with other weedy, small-flowered species in the genus, it is habitually self-pollinated and regularly sets seed (Garrard & Streeter 1983; Proctor et al. 1996, p. 332). When the fruits ripen, each of the five seeds is ejected explosively and thrown in a sling-like manner for a considerable distance (up to 6 m) out of its mericarp container, leaving the familiar and characteristic candelabra-like appearance of the discharged crane's-bill fruit (Yeo 1985, p. 33).

The seed is relatively large, oval, its surface pitted and it is heavy in comparison with many other agricultural weeds, weighing 0.002-0.003 g (Salisbury 1964). The seed production per plant is very variable, often ranging from 50-200 (Guyot et al.1962), but a large plant may produce 10,000 to 20,000 seeds (Salisbury 1964). Germination of seed shed in the summer begins in July and extends in an intermittent manner throughout the autumn into November in mild years. By the end of the year, between 18-59% of seeds have germinated and appreciable numbers of seeds continue to germinate intermittently during the following year, mainly from May-September, peaking in mid-June. They continue to germinate over the following four or more years. The timing of emergence within this period is largely determined by soil moisture and to a lesser extent by cultivation disturbance in early summer (Salisbury 1964, Fig. 28 & p. 320; Roberts & Boddrell 1985).

Fermanagh occurrence

G. dissectum is widely but rather thinly scattered throughout the whole VC, being represented in 84 tetrads, 15.9% of those in the VC. Nine of these tetrads contain only pre-1975 records, which suggests a definite decline in suitable habitats, or perhaps cleaner sown seed mixtures.

British and Irish occurrence

G. dissectum is widespread and common throughout the whole of B & I, except in a few areas of C & W Ireland and C & N Scotland, where it becomes scarce or absent. The ability of the species to compete and thrive in nutrient-rich disturbed habitats makes it likely that it is increasing its range northwards and becoming more abundant in many areas of B & I (S.J. Leach, in: Preston et al. 2002).

At the hectad scale in the New Atlas maps, G. dissectum appears as common and ubiquitous as G. robertianum (Herb-Robert) in NI. However, this certainly is not the case; Cut-leaved Crane's-bill is very much more occasional or even casual in many of its cultivated or more transitory wayside and waste ground habitats than is G. robertianum. The comparative post-1975 statistics for Fermanagh are: G. robertianum 1156 records in 450 tetrads while for G. dissectum the figures are 104 records in just 70 tetrads.

British status revised

Before the 20th century seed cleaning techniques were developed, G. dissectum frequently was a large-scale seed contaminant of clover mixtures, particularly affecting seed of Trifolium incarnatum (Crimson Clover), which was extensively cultivated in S England towards the middle of the 19th century. Up to 50% of the seed sown as clover could actually be Cut-leaved Crane's-bill. However, more normal contamination levels would have been closer to 5% (Salisbury 1964, pp. 136, 167).

The weedy behaviour and persistent seed bank of G. dissectum, together with the fact that the only fossil evidence of the species presence in B & I from the current Flandrian interglacial (= Littletonian in Ireland) is from two archaeological sites of the Roman period (100-400 AD) (Godwin 1975) has resulted in a recent revision of the plant's status. The New Atlas is the first floristic publication to regard G. dissectum as an archaeophyte throughout B & I, ie an ancient or pre-1500 AD introduction. In the light of this recent modification, The current author (RSF) regards it a little surprising that the same change of status was not applied to G. molle (Dove's-foot Crane's-bill) and possibly also to G. lucidum (Shining Crane's-bill), two further Crane's-bills of very similar biology, ecology and fossil history to G. dissectum.

European and world occurrence

Cut-leaved Crane's-bill is believed to have originated in Europe and W Asia and it is widespread in S, W & C Europe, along the Mediterranean coast of NW Africa and in Macaronesia. In a discontinuous manner, it extends eastwards in southerly latitudes only reaching the Caspian Sea. Northwards the species stretches up the Atlantic and Baltic coasts of Scandinavia and crosses the Arctic Circle, but probably only with the assistance of man. It is very widely dispersed across the globe as a naturalised introduction in regions including Iceland, the W Himalaya, N & S America, the Cape Province of S Africa, New Guinea, Australia and New Zealand (Hultén & Fries 1986, Map 1272). It was first recorded in New Zealand in 1940, but recently has become a prominent weed of arable land, especially in N and E South Island (Webb et al. 1988).

Names

The Latin specific epithet 'dissectum' means 'deeply cut', referring very aptly to the upper leaves (Gilbert-Carter 1964). The most frequent English common name is simply a translation of the Latin species name, but there are two alternatives, 'Jagged Crane's-bill' (Watts 2000), which is not accurate and deserves to be ignored and a much more interesting name 'Pink Needle' (Britten & Holland 1886), which they suggest Lyte (1578, p. 48) applied to this species. Prior (1879), however, followed William Turner's Herball (1551-68) and referred this name to Erodium moschatum (Musk Stork’s-bill) and E. cicutarium (Common Stork’s-bill) (see also Grigson's account of these two species in his Englishman's Flora (1955 & 1987)). Prior suggested the derivation was due to the long tapering fruit awn resembling the needle used in pinking, ie for making eyelet holes like pinks, in muslin (Prior 1879, p. 185). 'Pink Needle' is a name sometimes also given to Scandix pecten-veneris (Shepherd's Needle).

Threats

None.

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