Geranium molle L., Dove's-foot Crane's-bill

Account Summary

Growth form and preferred habitats

A small, spreading, or if supported, quite large, 10-50 cm, climbing, softly hairy winter annual or biennial, G. molle is not a common species in Fermanagh, nor indeed in the N & W of Ireland generally, although it is widespread and common throughout most of Britain and some parts of Ireland (see below). It grows in a wide array of open, lowland habitats and is probably most frequently found in dry to droughted, often shallow calcareous or sandy, open, sunny, regularly disturbed wayside or grassland sites (Grime et al. 1988, 2007). It also appears locally on sandy lakeshores. In other regions of these islands, but not in Fermanagh, it is commonly found in arable fields and on sand dunes (arable farming is virtually extinct in Fermanagh). G. molle also regularly crops up in what can be regarded as permanently open sites, eg in rock crevices, screes and on walls (Segal 1969; Rodwell et al. 2000, eg community types OV38 and OV39).

In all these different situations, ecologically it behaves as a stress-tolerant, ruderal weedy species, avoiding competition from taller and more vigorous perennials. It achieves this avoidance by colonising conditions that are too dry, disturbed, or nutrient-impoverished to allow perennials to grow aggressively and thrive (Grime et al. 1988, 2007). It is therefore quite possible that in the N & W of Ireland and, indeed, in similar, but usually somewhat more upland regions of Scotland, the climate is consistently simply too wet and, perhaps, the soils excessively acidic (it prefers a pH above 5.0) to allow G. molle to compete and be as frequent as it is elsewhere in these islands.

Like its even more common, but much more shade-tolerant relative, G. robertianum (Herb Robert), G. molle often overwinters as a small, green rosette of downy, dissected leaves on a short, erect or decumbent stem attached to a quite long, penetrating taproot. Like Herb Robert, the bruised leaves are unpleasantly pungent, the odour somewhat reminiscent of mouse, a feature which, along with their excessive glandular hairiness, appears sufficient to deter the depredations of herbivores.

Variation

There are no subspecies described for G. molle, but four varieties have been distinguished and named in Sell & Murrell (2009). These are var. arenarium N. Terrace, a form that produces a plant lying flat to the ground in a circle, with leaves 0.5-3.0 cm in diameter, flowers 5-6 mm in diameter, and with ribbed mericarp fruits; var. molle, is an erect or ascending plant with leaves 1.5-5.0 cm in diameter, flowers 5-8 mm diameter and mericarps ribbed; var. aequale Bab. is an erect plant with leaves 1-3 cm in diameter, flowers 5-6 mm in diameter and mericarps smooth and without ribs; and var. grandiflorum Vis. is another erect plant with leaves 3-6 cm in diameter, much larger flowers 9-13 mm in diameter and with mericarps ribbed.

Var. molle is the widespread plant, while var. arenarium is an ecotype of sandy soils near the coast and sandy heaths inland, occasionally found elsewhere.

The distribution of var. aequale is unknown while var. grandiflorum occurs in scattered localities across S Britain and in Continental Europe (Sell & Murrell 2009).

Fermanagh occurrence

G. molle has been recorded in 25 tetrads, 4.7% of those in the VC. It is only occasional and thinly scattered in the survey area, but as the tetrad map clearly shows, it is much more frequent in the eastern half of the county, there only being two tetrads with records in all the ground to the W of Lough Erne. Other habitats where there are rare Fermanagh occurrences include disturbed upland pastures, roadside verges, quarries, bridges, urban walls and car parks.

Flowering reproduction

G. molle flowers from April onwards, continuing throughout the summer until September, the timing dependent upon the favourability – or lack of it – of the local environment. In shallow, lighter, drier soils, plants have already completed their flowering and fruiting cycle by the beginning of June, a situation which might sometimes allow more than one generation within a growing season as happens with other successful small weedy annuals such as Senecio vulgaris (Groundsel) and Capsella bursa-pastoris (Shepherd's-purse). Although the current author (RSF) does not know of any detailed population study of G. molle, I certainly would expect that two or three 'cohorts' of seedlings germinating in different periods of the growing season might complete their life-cycle during a single year, as is known to be the case for G. robertianum (Falinska & Piroznikow 1983).

Habitual self-pollination

The paired, mauve or pale pink flowers with their distinctive deeply notched petals, barely longer than the sepals, must originally have evolved to attract insects to carry out cross-pollination. The degree to which this strategy still occurs requires more study to elucidate, but nowadays it appears that flowers of G. molle habitually self-pollinate. The selfing process is described as 'automatic', the small, self-compatible flowers having their anthers and stigmas borne on the receptacle in close proximity and maturing simultaneously. The transition from reliance on an external agency of pollen transport to an automatic selfing breeding system is a common strategy adopted by many small, ephemeral, annuals, many of which live only a few weeks rather than the year which the term 'annual' suggests. They appear to have evolved this very reliable reproductive method to enhance the chances of their survival in unpredictable, open, often harsh physical and chemical environments. There is a balance of advantages and disadvantages to the various strategies of pollination and fertilisation and a continuum of variation exists between the two extreme types of sexual reproductive mechanism. Furthermore, as has also been seen to be the case with Poppies (Papaver spp.) and other weedy plants, a species may only require the occurrence of a very occasional cross-fertilisation to replenish population variation and to maintain its much longer-term genetic options (Proctor et al. 1996, pp. 330-3).

Seed size and natural dispersal

In comparison with many other common, more or less ephemeral weeds, G. molle seed is quite large, weighing on average 0.001539 g. This is five times heavier than seed of Senecio vulgaris and three times that of Stellaria media (Common Chickweed), two species with which Dove's-foot often associates (Salisbury 1942, Table 9; Rodwell et al. 2000, OV5, p. 345)). Apart from the characteristic Crane's-bill jerked, sling-shot mechanical seed release of the Geranium genus, viable seed samples of G. molle have been recovered from the dung of cows and Wood-pigeon, both of which obviously must feed on the plant and transport it (Ridley 1930, pp. 361, 498).

Seed dispersal by man

In addition, in past years, G. molle was widely disseminated through being a frequent and, occasionally, a rather large-scale contaminant of commercial clover seed mixtures (Salisbury 1964). Another means of accidental long distance dispersal by man was in ships' ballast, or in the discarded dung of transported cattle. G. molle features in a long list of European species introduced and recorded in Philadelphia on dumped ballast heaps of this nature, given by Ridley (1930, p. 646).

Seed germination and persistence in soil seed bank

After an experimental sowing made by Roberts & Boddrell (1985) at the end of July, 11% of seed germinated in the first autumn, followed by appreciable numbers in each of the following four years, so a persistent soil seed bank clearly exists. In this particular study seedlings emerged in a consistent pattern, mainly from May to September, the timing largely determined by soil moisture, but with a main flush following a programmed soil disturbance in mid-June simulating cultivation (Roberts & Boddrell 1985).

Possible confusion with G. pusillum: G. molle is rather similar in appearance and ecology to G. pusillum (Small-flowered Crane's-bill – another frightful English common book name), but it has larger, more spreading and more deeply notched petals and hairless, ribbed mericarps (although the actual seeds are smooth and brown) (Butcher 1961; Yeo 1985). The two species are said to be capable of hybridizing (Stace 1975) and undoubtedly they are sometimes confused.

In NI, G. pusillum has been very rarely recorded in Cos Down (H36) and Tyrone (H38), where it is regarded as an introduction, while elsewhere in S & E Ireland and in Britain, where it is a much more frequent and widespread species, Small-flowered Crane's-bill is considered a native (Preston et al. 2002).

British and Irish occurrence

G. molle is native, common and widespread throughout lowland Britain ascending to around 550 m. It becomes less common and more scattered northwards in Scotland (New Atlas). In Ireland, it is also quite common and widespread, although most frequent in the E & S and increasingly scattered westwards, where it again becomes more obviously confined to coastal sites. Being so widely introduced elsewhere in the world, the current author (RSF) feels it worth considering that the patchy Irish distribution of G. molle might represent the outcome of many repeated accidental introductions, stemming from a native range that, as the New Atlas map proves, is much more consolidated in the warmer lowland areas of the southern half of Britain.

European and world occurrence

G. molle is indigenous and widespread in all of S Europe, eastwards to the Balkan Peninsula and northwards to S Sweden. Beyond this it is much more scattered and occasional, but stretches to the W Himalaya and, in Scandinavia, to the N Baltic. It is also present in N Africa and the Atlantic Isles. Beyond this, it has been widely spread as a weed of cultivation in parts of Scandinavia, C Russia, Iceland, The Faeroes, S Africa, N Japan, N & S America, Australia and New Zealand (Hultén & Fries 1986, Map 1269).

Names

The Latin specific epithet 'molle' means 'soft', an easily appreciated reference to the characteristic dense coat of soft hairs on the leaves. The English common names 'Dove's-foot' (16th century), or 'Dove's-foot Crane's-bill' if we absolutely must (!) (20th century) and the older 'Culverfoot' (15th century), derive as direct translations of the medieval Latin herbalist's name 'pes columbae' or 'pes columbinus', dove and culver being alternative names for pigeon. The shape of the leaf is erroneously supposed to resemble a pigeon's foot, but the soft hairiness of the whole plant is reminiscent of the bird's downy feathers. In other European countries, this name referred to G. columbinum, but in B & I, G. molle is the commoner species, so the name was transferred (Dony et al. 1974; Grigson 1974; Watts 2000).

Grigson (1955 & 1987) lists a few alternative English common names, all of which are interesting but decidedly puzzling in their derivation, eg 'Dolly Soldiers', 'Jam Tarts', 'Mother of millions' and 'Starlights'. The latter author tells us that the plant was used like Herb Robert as a vulnerary to staunch bleeding. Nicholas Culpeper (1653), whose herbal ran to over a hundred editions, recommended Dove's-foot for a list of cures almost identical to those attributed to G. robertianum (see the species account on this webpage), and he memorably described it as, "a very gentle, though martial plant".

Threats

None.

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