Veronica filiformis Sm., Slender Speedwell
Account Summary
Introduction, neophyte, frequent and widespread.
1949; MCM & D; Aghalane Bridge, Woodford River.
Throughout the year.
Growth form and reproduction
A small, downy, prostrate creeping, but rampant mat- or carpet-forming perennial, most commonly found as an aggressive invasive weed of garden lawns, where it can quickly become a problem. Although it flowers freely from April to June, the solitary, attractive, pale lilac-blue flowers, formed on long, thread-like stalks (pedicels 6-8 times longer than leaves) in the axils of ordinary leaves are self-sterile and do not (or only extremely rarely) form capsules and seeds in B & I (Perring & Walters 1989; Ellis 1993). Salisbury (1962) suggested that the sterility probably arose because all the plants in Britain belong to the same source or mating strain and thus constitute a single self-incompatible clone. In this connection, it is important to bear in mind that few self-incompatibility systems are absolute (Stace & Crawley 2015).
It is not known for certain whether more than one mating strain exists in B & I, but the fact remains, seedlings of V. filiformis have never been seen in B & I (Bangerter & Kent 1957). However, the slender, wiry, creeping stems or runners, up to 50 cm long, spread rapidly and readily root at their nodes. When it invades lawns, V. filiformis becomes a very close and firm creeper and is as hard to remove as the native V. serpyllifolia (Thyme-leaved Speedwell). Stem fragments are also extremely successful at regenerating the plant from mown clippings, some of which may also disperse considerable distances in strong winds (Ellis 1993). Vegetative material of the species is probably also transported in contaminated soil, turves used for laying new lawns and in garden plant pots. It could also be a contaminant on contractors' lawn mowers, strimmers and other machinery (Stace & Crawley 2015).
Introduction, spread and preferred habitats
The species was introduced to B & I from Turkey and the Caucasus as a small decorative subject for rock gardens in the early 19th century, perhaps as early as 1800, but certainly by 1808. In its native area, V. filiformis is a rare plant with a very restricted range that grows in woods, fields and pastures. Even in its native habitat and environment, the species forms few seeds (Bangerter & Kent 1957). It was first reported as having escaped from garden confines in England in the neighbourhood of Colchester in 1838, and the second report was 89 years later by the River Ayr in Scotland in 1927 (Bangerter & Kent 1962). In the following 25 years, it spread slowly at first and then, post-1950, quite rapidly across B & I. Unlike other field speedwell species, its ability to colonise is not confined to open and bare ground. It now is an abundantly naturalised adventive, forming patches on grassy waysides, stream-side meadows and pastures throughout most of the British Isles. It also remains a serious park and garden weed and major lawn pest (Bangerter & Kent 1957; Ellis 1993; Stace & Crawley 2015).
Fermanagh occurrence
As the tetrad map indicates, V. filiformis is frequent and widespread across Fermanagh, having been recorded in 129 tetrads, 24.4% of those in the VC. It is found typically in pastures, roadside verges, disturbed ground, quarries and on riverbanks and lakeshores, but it most commonly occurs as a weed of lawns.
Irish occurrence
V. filiformis was first reported as a garden escape in Ireland from Ballina, W Mayo (H27) around 1933, secondly at Wicklow (H20) in 1935 and thirdly on a grassy bank between Sligo town and Ben Bulben mountain (H28). In 1938, it was found at Greencastle, E Donegal (H34) and in 1946 on sand dunes at Strandhill, Co Sligo (H28) (Bangerter & Kent 1957). By 1957, records had been made from 39 sites and by 1961 this had increased to around 100 (Bangerter & Kent 1957, 1962). It is now, as in Britain, a widespread and common, lowland garden escape, naturalised in lawns and other managed grassland, suburban and other grassy verges and waste ground. It also appears less frequently in more natural habitats, particularly on the banks of streams and rivers (Reynolds 2002).
The New Atlas hectad map indicates a very much more complete coverage of the VCs in the north of the island, but it also shows a greater presence (or more persistent recording effort) around the cities of Dublin and Cork, while the species appears less prevalent in the far west of the Republic, especially in Co Clare (H9), E & W Mayo (H26 & H27) and S Kerry (H1) (A. Horsfall, in: Preston et al. 2002). It will be interesting to compare how the species has been recorded in the forthcoming BSBI Altas 2020 to be published in 2023.
British occurrence
The maps of Slender Speedwell distribution published by Bangerter & Kent in 1957 and 1962 showed the species' presence extending from the Channel Isles to the far N of Scotland, a range almost as wide as that found today (A. Horsfall, in: Preston et al. 2002). However, in the second half of the 20th century, the distribution became very greatly consolidated and extended across the sea to Orkney and Shetland.
V. filiformis has become an extremely common, widespread and locally abundant invasive perennial across the whole of lowland Britain in a wide range of habitats from garden lawns and gravel paths to churchyards, to artificial and semi-natural sites, including roadsides, paths, rubbish heaps, grassy banks (especially near houses), plus along streamsides. It is probably most abundant in S & W England, but in parts of S & SW of England in the late 1940s it was described as being dominant over native vegetation in some sites (Bangerter & Kent 1957).
It has been mooted that anecdotal evidence indicates a decline in the species presence has been noticed since around 1995 (Stace & Crawley 2015), although the Change in the British Flora 1987-2004 survey suggested it is still increasing (Braithwaite et al. 2006).
European and world occurrence
During the 20th century, V. filiformis spread to many areas of N & W Europe and also to both E & W regions of N America and New Zealand, where it was first recorded in 1981 (Hultén & Fries 1986, Map 1661; Webb et al. 1988).
Names
The Latin specific epithet 'filiformis' means 'threat-like', from 'filum', 'thread', and 'forma', 'shape', an obvious reference to the slender, wiry, spreading stems (Gilbert-Carter 1964).
V. filiformis has been given a number of English common names including 'Slender Speedwell', 'Creeping Speedwell', 'Threadstalk Speedwell', 'Round-leaved Speedwell', 'Caucasian Speedwell' and 'Whetzel Weed'.
Threats
An invasive weed of mown or heavily grazed grasslands, in Fermanagh V. filiformis is now also actively colonising semi-natural grasslands beside riverbanks and lakeshores and it has arrived in the NR of Hanging Rock.