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Convolvulus arvensis L., Field Bindweed

Account Summary

Native, rare. Eurosiberian southern-temperate, but widely naturalised and now circumpolar.

1872; Brenan, Rev. S.A.; Co Fermanagh.

March to October.

Growth form and preferred habitats

Convolvulus has small bracteoles, borne some distance below the calyx, which readily distinguishes it from all Calystegia species. The funnel-shaped flowers of Convolvulus arvensis are much smaller than those of any Calystegia species we have in Ireland (only 15-40 mm in diameter) and their colour varies from white to deep rose-pink, or striped with both colours. Leaves are glabrous, alternate, stalked and arrow-shaped (ie hastate) (An Irish Flora 1996; New Flora of the BI 1997).

Like the several Calystegia species in B & I, C. arvensis is a deeply-penetrating, slender, extensively-branching, rhizomatous, perennial of warm, light, fertile, less acidic soils (pH greater than 4.5), which dies down completely in the autumn. Stems are numerous and are either procumbent, or erect and twining on support provided by adjacent plant stems or slender inanimate structures, usually reaching a height of around 60 cm. It never twines around anything of bulky dimensions, such as for instance, gateposts (Grieve 1931, p. 220). Twining is anti-clockwise, the stem taking about two hours per revolution, and often strangling its support. C. arvensis is most abundant when colonising recently disturbed sites, particularly in cultivated ground and, since arable agriculture has almost completely ceased in Fermanagh, locally this now really means plots and plants in gardens (Melderis & Bangerter 1955; Grime et al. 1988, 2007).

The typical habitat of Field Bindweed is lowland, disturbed waste or cultivated ground and it is frequently found along less disturbed, more-or-less unmanaged linear habitats, such as hedgerows and along lakeshores, roads and railways, a pattern which can just be detected in its scarce or rare Fermanagh occurrences. It demonstrates a strong preference for fertile soils and is absent from very infertile ones (Grime et al. 1988, 2007).

Roots and rhizome can penetrate very deeply (down to 9 m), twining like the aerial stems around the roots of other garden plants and making eradication of the species very difficult or impossible. The underground parts can spread extremely rapidly in cultivated soil, infecting almost 30 m2 in a single season (Salisbury 1964). Since it roots so deeply, C. arvensis is absent from wet ground and it readily survives drought when growing on cliffs and rock outcrops. It is sufficiently rare in Britain above c 200 m that a temperature limitation is suspected (Grime et al. 1988, 2007).

The plant can regrow from the tiniest fragment of root or rhizome left in the soil, making it, as many gardeners know, almost impossible to eradicate and very difficult to control. The established strategy of the species is categorised as Competitive-ruderal. It is absent from regularly grazed or mown ground and also from situations providing heavy shade (Grime et al. 1988, 2007).

Variation

A very variable species, no fewer than eleven forma have been described in C. arvensis, based largely on colour variants of the corolla, anthers and filaments (Sell & Murrell 2009). Corolla colour appears to be constant when plants are grown from seed (Proctor et al. 1996). In Europe, ecotypes based on leaf shape and flower colour have been recognised (Weaver & Riley 1982).

Fermanagh occurrence

There are records from a total of ten tetrads in the Fermanagh Flora Database, eight of which are of post-1975 date. The sites are thinly scattered in the lowlands and they range from roadside hedgerows, to waste ground and gardens.

Flowering reproduction

C. arvensis is a polycarpic perennial, the decorative, funnel-shaped flowers of which are produced in axillary cymes of 1-4 flowers from June to September. Each blossom last just a single day, the corolla unfolding around 7 a.m. and closing about 10 p.m. or earlier in bad weather. The faint vanilla-like perfume of the flower attracts bees and a variety of flies including hoverflies which collect a nectar reward when transferring pollen. Nectar is secreted at the base of the ovary, but can only be reached through five narrow passages between the broad bases of the stamens. This is referred to as a 'revolver flower', since the insect is delayed inside the funnel-shaped corolla, visiting the separate 'chambers', to reach all of the nectar reward (Proctor et al. 1996). It is believed that self-pollination may also take place.

Irrespective of the pollination mechanism, seed set, which takes place from August to October, is probably restricted in B & I by low temperatures, only happening in hot summers (Thurston 1960). The fruit capsule is small, about 6 mm in diameter, ovoid and contains between 1-4 relatively large, 3.5 mm, minutely pitted seeds. The seeds can survive burial for at least six years and may indeed be as long-lived as those of Calystegia sepium subsp. sepium (Salisbury 1964), a view supported by evidence presented in the soil seed bank survey of NW Europe (Thompson et al. 1997).

Seed dispersal

Seed of C. arvensis can float for about twelve hours and can therefore be water dispersed along streams or in rainwater runoff. Alternatively, they may be eaten by birds and carried in their crops (Ridley 1930). Nowadays, man probably is another major agent of dispersal however, with seed and small fragments of root or rhizome being all that is necessary to transport the species in soil, on the roots of other plants, or in mud on boots or on vehicles.

Species management

The plant is very difficult to control, even with modern herbicide sprays, since the hairless leaves and stems are rather waxy and difficult to wet. The plants also show ecotypic resistance to 2,4-D herbicide. While the tops may be killed by the chemical spray, portions of the underground system usually manage to survive. The best level of control (actual eradication is almost impossible) is achieved by spraying just prior to the plant flowering (Muzik 1970).

British and Irish occurrence

In Britain, there is fossil pollen evidence from the Flandrian zone V proving C. arvensis is native. Later fossil records from zone VIII show the species present in Anglo-Saxon and Norman levels amongst other weeds of arable ground (Godwin 1975). Field Bindweed, which probably originated in the Mediterranean region, is very common in Britain throughout the southern lowlands, but it becomes much less frequent and more coastal N of a line between Hartlepool and Heysham.

In Ireland, C. arvensis is very widespread and scattered and while it has been recorded in every Irish VC (Cen Cat Fl Ir 2), there is a greater prevalence of it near coasts and it is noticeably more frequent in the eastern half of the island (New Atlas).

European and world occurrence

Thought to have originated in the Mediterranean region, C. arvensis is widespread in temperate Eurasia, including N Africa, the Azores and Macronesia, but it is absent in more northerly boreal parts. In phytogeographical terms, it is described as Eurosiberian southern-temperate. A very variable species, C. arvensis has spread widely as a weed of arable cultivation to C & S Africa, Ethiopia, S Arabia, N & S America, Japan, S Australia and New Zealand, so that its distribution is now discontinuously Circumpolar (Hultén & Fries 1986, Map 1538).

Names

The genus name 'Convolvulus' is from the Latin 'convolvo', to entwine or roll around and it first appeared in Pliny (Gilbert-Carter 1964; Stearn 1992). The Latin specific epithet 'arvensis' means 'of ploughed fields', or 'of cultivated fields' ('arvum' (solum) translates as 'arable land') (Gilbert-Carter 1964; Gledhill 1985).

There are a large number of local English common names – around 30 in Grigson (1955, 1987), many shared with Calystegia sepium (Hedge Bindweed), for example, 'Bellbind' and 'Old Man's Nightcap' (the old man being the Devil). Due to its twining habit, the plant has acquired names such as 'Bearbind', 'Bedbind', 'Wheatwind', 'Withwind', 'Cornbine' or 'Cornbind' and 'Ropebind', but the current author likes 'Devil's Guts' and 'Hellweed' best, since they conjure up the gardeners' deep-seated hatred of this pernicious, extremely persistent weed.

Threats

None.