Fallopia convolvulus (L.) Á. Löve, Black-bindweed

Account Summary

Growth form and preferred habitats

Black-bindweed is a tiny-flowered, summer annual possessing a taproot, an efficient nutrient-gathering fibrous root system, and a sprawling, rapidly increasing, smothering, vine-like stem that develops a twining climbing habit when tall supporting plants are available.

It is a pioneer colonist of disturbed, open, lowland, unshaded bare ground. Previously an annual weed of arable cultivation, it now appears mainly as a garden weed or as scattered individual plants on roadsides, rubbish tips and in disturbed waste ground or on rubble in building sites (Lousley & Kent 1981; J.R. Akeroyd, in: Preston et al. 2002).

Reproduction

As an annual, F. convolvulus reproduces entirely by seed. It flowers from July to October, producing cymose clusters of greenish-white flowers, many congested at the top of the stem and individual cymes of up to 8 flowers borne in leaf axils lower down. The flowers are bisexual and are insect- or self-pollinated, sometimes cleistogamous (ie fertilised while still in bud). Seeds are prolifically produced and are long persistent in the soil seed bank (Grime et al. 1988).

Fermanagh occurrence

There are records of F. convolvulus in the Fermanagh Flora Database from a total of 20 tetrads, but only 14 of them have post-1975 finds. The pattern of Fermanagh records provides slight circumstantial evidence of a species decline, but it forms part of a wider trend within N England and Scotland whereby F. convolvulus has gradually disappeared from marginal areas where cultivation has been abandoned (J.R. Akeroyd, in: Preston et al. 2002).

In Ireland, the change from a mixed arable and pastoral pattern of farming towards almost exclusively pastoral agriculture began immediately after the potato famines of the 1840s and the associated human de-population. Apart from brief reversions during both world wars, this process has continued to the present day and arable cultivation has almost reached extinction in Fermanagh. Consequent to this, Black-bindweed is rare in Fermanagh but is most frequently found on suitable open ground around the quarries in the Derrylin area. Since it possesses a long-persistent seed bank, the species also crops up sporadically on heaps of disturbed topsoil in other parts of the VC, eg around building sites.

Irish occurrence

The Cen Cat Fl Ir 2 lists Black-bindweed as having been recorded in every Irish VC, but while still widespread, it has been in decline for a long period, perhaps for 180 years. Nowadays, Fermanagh is near the north-westerly inland Irish limit of this weedy annual, and indeed in Donegal (H34, H35) it appears largely coastal (BSBI Atlas 2; New Atlas).

British occurrence

Although elsewhere within its overall distribution F. convolvulus occurs very much further north (for instance at 70N in Greenland), within Britain and Ireland the species shows a definite thinning towards both N & W throughout these islands.

Species status

Previously accepted as a native species without question by most British and Irish authorities (eg Stace 1997), Webb (1985) listed F. convolvulus along with 40 other species as being, in his opinion, probably or almost certainly introduced by man. It is odd that the introduced status of this common weed should only recently have been recognised and acknowledged (Preston et al. 2002; Preston et al. 2004). F. convolvulus has been very closely associated with human agricultural activities since recorded history began, and its seeds or achenes are a notorious, almost cosmopolitan crop seed contaminant, especially of cereals. In many parts of the world, it is regarded as the number one weed of a wide variety of arable crops (Holm et al. 1977). It is odd that Sell & Murrell (2018) revert to regarding F. convolvulus a native species.

Fossil record

While there are fossil records of F. convolvulus from earlier interglacial periods, in the current warm period there are no pre-Neolithic fossils which would indicate its presence before farming got underway (Godwin 1975). The discovery of large accumulations of seed in some archaeological digs strongly suggests that the seed was an important source of food or fodder (Hume et al. 1983).

European and world occurrence

F. convolvulus is common and widespread across the whole of Europe, although the distribution thins towards the south as it approaches the Mediterranean coast (Jalas & Suominen 1979, Map 420). Black-bindweed spreads widely with agriculture as an arable crop seed contaminant, and it is now virtually cosmopolitan. In many parts of the world, it is regarded as the number one weed of a wide variety of arable crops, and in other areas including Argentina, Canada and the United States it is in the top three cereal weeds. It has increased in seriousness due to its prolific seed production, deep dormancy and long seed persistence in soil, its habit of germinating throughout the growing season, and its resistance to herbicides. As other weeds more susceptible to herbicides are removed from the field, competition is effectively reduced, allowing F. convolvulus to flourish (Holm et al. 1977).

Names

The genus name 'Fallopia' was given in honour of Gabriele Fallopi (1523-1562), the Italian anatomist, after whom the Fallopian tube was also named. The Latin specific epithet 'convolvulus' is derived from 'convolvo' meaning 'roll around' or 'interweave' (Gilbert-Carter 1964). Synonyms include Polygonum convolvulus L., Bilderdykia convolvulus (L.) Dumort, Fagopyrum convolvulus (L.) H. Gross, Fagopyrum carinatum Moench, Helxine convolvulus (L.) Raf., Reynoutria convolvulus (L.) Shinners and Tiniaria convolvulus (L.) Webb & Moq. Other English common names include Bearbind, Bindcorn, Climbing Bindweed, Climbing Buckwheat, Cornbind, Corn Bindweed, Devil's Tether and Wild Buckwheat.

Threats

The continuing decline in arable agriculture limits the availability of open sites suitable for this species.

Rumex acetosella L., Sheep's Sorrel

Native, very frequent and widely scattered throughout. Eurosiberian wide-temperate, but widely naturalised around the world and now circumpolar.

1881; Stewart, S.A.; Co Fermanagh.

Throughout the year.

Growth form and preferred habitats

This often small but rapidly growing, 4-30 cm tall, creeping, clump and patch-forming rhizomatous perennial is a characteristic early, but rather persistent, coloniser of unshaded, open or disturbed ground, both lowland and upland. It is typically found on infertile acidic, relatively dry, sandy, stony and peaty soils, including those on overgrazed pastures, heaths, bogs and grassy moorland. The lanceolate, hastate (spear-shaped) leaves with their small, spreading basal lobes are very distinctive and their strong, acid taste confirms identification.

It is an occasional to frequent weed in urban situations, on roadsides and in waste ground, sand-pits and quarries. Nowadays, it is also very often found growing in the peaty composts used in garden centre plant pots. Being low-growing, it is a poor competitor with taller herbs and grasses and therefore it is confined to very infertile, disturbed, or physically limited conditions for growth. Sheep's Sorrel is also an early coloniser of freshly available bare soil and of vacant rock crevices. The plant is especially linked with recently burnt ground in peaty areas, eg on cleared ground in forestry plantations, around cut-over areas of bogs and in fired areas of heathland. R. acetosella also survives in narrow rock crevices on cliffs and outcrops, in situations where competition is much reduced or absent.

Variation

R. acetosella is a polymorphic and very widespread circumpolar species within which there is an intricate and taxonomically not fully worked out range of variation (Hultén & Fries 1986). The chromosome base number is x=7 and three levels of ploidy are known to occur (2x, 4x and 6x). However, study shows there appears to be only minor correspondence between ploidy level and either morphology (including size characters and leaf shape) or distribution. Taxonomic distinctions are based on morphologically defined variants, and several ploidy levels may co-exist within each described taxon (Jonsell et al. 2000).

Stace (2010) recognises two subspecies in B & I, although their distribution is not yet adequately researched. The more widespread form is named subsp. acetosella (R. tenuifolius (Wallr.) Á. Löve), which very likely covers both islands. A small form of this plant, with narrow, linear leaves that is ± confined to very dry coastal sands previously described as R. tenuifolius (Wallr.) Á. Löve, is treated as a mere variety by Stace (2010), namely var. tenuifolius Wallr. The less widespread of two subspecies he recognises is subsp. pyrenaicus (Pourr.) Akeroyd (subsp. angiocarpus auct. non (Murb.) Murb., R. angiocarpus auct. non Murb.). This form probably is mainly located in the S of Britain and appears to be absent in the N, although the distribution and ecology of the two subspecies very likely overlap as they do in continental Europe.

In their recent, critical consideration, Sell & Murrell (2018) relocate R. acetosella to a genus on its own, naming it Acetosella vulgaris (Meisn.) Fourr. They also recognise three subspecies within it: subsp. vulgaris, subsp. tenuifolia (Wallr.) P.D. Sell and subsp. pyrenaica (Pourr. ex Lapeyr.) P.D. Sell. Subsp. pyrenaica is distinguished by having its inner perianth segments fused to the achene, while subsp. tenuifolia, as its name suggests, has narrow basal leaf lobes, usually 5–15 times as long as wide, usually curved forwards, separating it from subsp. vulgaris (basal leaf lobes wider, usually 2-7 times as long as wide and usually patent, directed backward, or occasionally absent (Sell & Murrell 2018, pp. 512-3).

Fermanagh occurrence

In Fermanagh, R. acetosella has been recorded in 147 tetrads, 27.8% of those in the VC. Apart from the previously mentioned habitat types, it is also very common in many rocky upland areas, including in the area on the thin peaty soils developed over limestone on the Knockmore cliffs and the stabilised scree above Doagh Lough, as well as on the acidic rocks and slopes of Cuilcagh, the highest mountain. Having said that, Sheep's Sorrel is very definitely a calcifuge species; seedlings grow very poorly and the plant cannot compete for long in lime-rich growing conditions. Frequency and abundance measures elsewhere show R. acetosella strongly prefers acidic soils within the pH range 3.5-5.5 (Grime et al. 1988).

Although most frequent and abundant in disturbed, bare, peaty soils, Sheep's Sorrel can also be long persistent in short-turf, acidic, unproductive grassland, even when this type of ground is heavily grazed by sheep. The reason for this is at least partially accounted for by the sharp, bitter-tasting oxalates present in its tissues which deter some types of browser.

Toxicity

As the English common name (Sheep's Sorrel) suggests, livestock will graze on the plant, but since it is small in size they seldom consume large quantities. The species contains bitter-tasting oxalates that help deter browsers, and sometimes they also provide sufficiently high concentrations of nitrates that can cause poisoning. A third potential toxin is tentatively identified and called rumicin (Cooper & Johnson 1998).

Phenology and vegetative colony production

After seed germination in spring, the young plant develops a stout, deeply penetrating taproot early in its growth. This quickly gives rise to a spreading network of branching horizontal underground stems and shallowly running fibrous roots. Adventitious shoots are prolifically developed from the more shallow parts of the root system, which together with the rhizomatous growth, allows the individual plant clone to rapidly colonise and carpet the available open ground (Salisbury 1942, 1964).

Clonal colony development is very readily observed whenever R. acetosella first invades loose, sandy, bare or burnt soils to form a living carpet. A study in Canada found that a clone there could easily cover an area of 4 m² after just two growing seasons (Vezina et al. 1986).

Sexual reproduction

R. acetosella is a dioecious perennial with unisexual flowers on separate male and female plants. Plants flower from May to September and are wind-pollinated. Perhaps on account of its clonal growth and separate sexes, fruit production is sometimes poor. However, most plants produce some seed, and plants in favourable sites and seasons generate an abundance of it.

Seed dispersal

The seed or achene (a single-seeded dry fruit) is extremely lightweight, even in comparison with those of other species of open habitats. The seeds are often released surrounded by the persistent perianth and, despite the often small stature of the plant, they are dispersed readily enough by wind (Salisbury 1942). The fact that R. acetosella grows on cliffs and in rock crevices is further evidence of its excellent powers of dispersal, although in addition to carriage by wind this might be achieved through animal ingestion and internal transport. Regarding the latter dispersal mechanism, Ridley (1930) reported viable seed being excreted by birds, pigs, horses, cattle and goats.

Seed survival

The survey of soil seed banks of NW Europe uncovered no less than 52 estimates for this species, of which eleven recorded buried survival for at least five years (Thompson et al. 1997).

Fossil record

Fruit and pollen of R. acetosella s.l. are common in B & I throughout the interglacial and glacial fossil record from the Cromer Forest Bed series onwards. R. acetosella was prevalent (along with R. acetosa (Common Sorrel)) in all zones of the Late Weichselian, but it diminished greatly in zone IV of the Flandrian, probably in response to a closing of the herbaceous vegetation cover as the forest canopy developed. It does not reappear in the fossil record until there is evidence of deforestation brought about by human interference in the Bronze Age (Godwin 1975).

Fossil nutlets of R. acetosella agg. have been found in a full-glacial freshwater deposit of Middle Midlandian age, radio-carbon dated to 30,500 BP, discovered at Derryvree, near Maguiresbridge, Co Fermanagh (Colhoun et al. 1972). The flora and fauna of the deposit indicated that open tundra vegetation and a periglacial climate prevailed at the time when it was laid down.

British and Irish occurrence

R. acetosella s.l. is almost ubiquitous throughout these islands from the coast to the uplands. However, the two or three subspecies that have been taxonomically described in recent years are not yet sufficiently recorded to reveal the true pattern and extent of their occurrence (Preston et al. 2002). Subspecies or variety tenuifolia is described by Lousley & Kent (1981) as locally abundant on dry, humus-deficient, sandy soils and occurring commonly near the S and E coasts of England and Scotland from Dorset to Sutherland. It is also said to be present on inland heaths in Surrey (VC 17), Berkshire (VC 22) and the Breckland (VCs 25-28), with widespread scattered localities elsewhere, although the distribution is imperfectly known. This remains the case.

European and world occurrence

R. acetosella s.l. is common and widely distributed as a native species throughout Europe from the Mediterranean to the far N of Scandinavia (Jalas & Suominen 1979; Map 427). Having said this, from Europe it has been very widely dispersed as a weed in association with human movement and activities and has been introduced to N America and indeed almost worldwide (Hultén & Fries 1986, Map 658). R. acetosella s.l. is now boreal circumpolar and has also spread into the southern hemisphere, including most temperate and some tropical areas (Jonsell et al. 2000).

Names

The genus name 'Rumex' is an old Latin name for Sorrel from Pliny derived from the Latin 'rumo' to suck, from the Roman habit of sucking Sorrel leaves to allay thirst (Johnson & Smith 1946). The Latin specific epithet 'acetosella' is derived from 'acetum' meaning vinegar, from the acid taste of the plant. 'Acetosa' and 'Acetosella' were both pre-Linnaean names for Sorrel and any other plant with acid-tasting leaves (Gilbert-Carter 1964; Stearn 1992).

The English common name 'Sheep's Sorrel' or just 'Sheep Sorrel' is from the 14th century French 'surelle' or 'sorele', a diminutive from the Low German 'suur' meaning 'sour' or 'acid', a reference to the acidity of the leaves. As such it might be translated as either 'little acid plant' or 'little sour plant', both of which are appropriate (Prior 1879; Grigson 1974).

Threats

None.

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