Veronica anagallis-aquatica L., Blue Water-speedwell

Account Summary

Growth form and preferred habitats

This stout, fleshy, short-lived perennial aquatic and semi-aquatic speedwell regularly (probably predominantly) behaves as an annual, although it can sometimes overwinter. It occurs in similar wet ground near water and shallow, still or slow-moving aquatic habitats that V. beccabunga (Brooklime) occupies and sometimes the two species occur together, but it is much less frequent than the latter across the whole of B & I. Unlike Brooklime, V. anagallis-aquatica often occurs ± submerged as well as emergent in shallow water, as well as a terrestrial herb in ± wetland stands.

Again, like Brooklime, V. anagallis-aquatica has rather thick, fleshy, glabrous, hollow stems that in this case shortly creep, root and then ascend (Press & Short 1994). Plants are more erect than Brooklime, more leafy and branched, and grow somewhat taller and more luxuriant, usually between 20 and 60 cm in height, but capable of reaching 100 cm or more under optimal growing conditions, eg in Cyprus and New Zealand (Meikle 1985; Webb et al. 1988). The stem can become very stout, 4-angled and succulent, especially towards the base. The leaves are opposite, the lower ones oval, shortly stalked and scarcely toothed, the upper ones narrowly lanceolate, serrate towards the apex, stalkless and clasping the stem at their base (Butcher 1961). Upper leaves can vary enormously in size, 1.5-17 cm long by 0.8-3.5 cm wide (Meikle 1985). Submerged leaves are very membranous (Webb et al. 1988).

Blue Water-speedwell grows in shallow water or on bare or trampled broken ground by lakes, ponds, rivers, streams and ditches and in marshy grassland, fens, flooded water meadows and clay- and gravel-pits. It is mainly lowland, but does reach 380 m at Malham Tarn in the Yorkshire limestones (VC 62) (A. Horsfall, in: Preston et al. 2002). In flowing water, Blue Water-speedwell may persist as submerged vegetative stands, failing to flower but, when emergent, it flowers freely. Plants on fertile mud or silt by streams and rivers are larger and more vigorous than plants in less favourable, drier, or more infertile terrestrial sites.

V. anagallis-aquatica is probably less shade-tolerant and it appears more confined to lowland sites than V. beccabunga. The latter is able to persist in more shaded, taller vegetation and it often spreads onto damp ground around upland streams and flushes in a way that Blue Water-speedwell rarely does. Despite its quite frequent luxuriant growth, V. anagallis-aquatica is not a strongly competitive species in tall herb vegetation, for instance, lacking the climbing ability of V. scutellata (Marsh Speedwell). The difference in occurrence between V. beccabunga and V. anagallis-aquatica must reflect a greater ecological sensitivity in the latter, which appears to demonstrate less vigour in its vegetative and reproductive capabilities, both of which vary greatly with habitat conditions. The competitive and comparative features and adaptations of these Veronica species are clearly worthy of further detailed study (Preston & Croft 1997). Having said this, the established strategy of V. anagallis-aquatica is categorised as CR, meaning 'Competitive Ruderal' by Grime et al. (1988, 2007), that recognises the species does have a number of ecological traits that enable it to compete and establish successfully under some environmental conditions, including rapid germination and growth.

Also, there is an underlying genetic difference in that V. beccabunga is diploid, while both V. anagallis-aquatica and the closely-related V. catenata are tetraploids (Preston & Croft 1997). V. anagallis-aquatica is distinguished from V. beccabunga by its less fleshy stems and its stalk-less, oblong-lanceolate upper leaves, while it is readily separated from the very closely related V. catenata (Pink Water-speedwell) by its pale blue, rather than pale pink flowers. Separation of V. anagallis-aquatica, V. catenata and their probably quite commonly occurring hybrid, V. × lackschewitzii J.B. Keller is not possible without the presence of flowers and/or fruit (J.H. Burnett, in: Rich & Jermy 1998).

Flowering reproduction

If it is going to flower, V. anagallis-aquatica does so in July and August. The inflorescences are long, lax, slender, erect, leafless racemes borne in pairs in the axils of the upper leaves. The 15-40 (mean of 25) flowers in each raceme, 5-10 mm in diameter, are lilac-blue, pale blue, pinkish-lilac or rarely white, with strongly marked violet lines on the corolla. The flowers are visited by flies that cross-pollinate them, but self-pollination is also easily performed. The fruit capsule, 3-3.5 mm, is pale brown, orbicular (just longer than broad), inflated, slightly notched and hairless. It dehisces into four valves and the numerous seeds, 0.5-0.7 mm, are pale brown, elliptic to globular, flat on one side, convex on the other and smooth (Blamey & Grey-Wilson 1989; J.H. Burnett, in: Rich & Jermy 1998; Sell & Murrell 2007).

Seed dispersal is by wind and flowing water, or in mud transported on animals, including birds (particularly ducks) and on man, enabling colonisation of isolated lakelets, as well as man-made pools and pits (Ridley 1930, p. 547).

There are just two estimates of seed longevity in the survey of NW Europe soil seed banks, one of which regards the species as short-term persistent (ie seed surviving between one and five years), while the other recognises seed as being present, but unable to assign it with respect to its transient or longer-term survival (Thompson et al. 1997).

Vegetative reproduction

Early in their growth, young plants develop stolon-like lateral branches that send out adventitious roots and spread the plant vegetatively to form clonal mats (Preston & Croft 1997). In common with V. beccabunga, portions of colonies of V. anagallis-aquatica can dislodge or branches fragment when flowing water is in flood spate and these can root and establish downstream, spreading the species vegetatively (Haslam 1978). As reproduction is by both seed and vegetative fragmentation, it is not clear which in this case is the more ecologically significant method of increase, although seed is obviously required in the longer term in order for the species to be biologically capable of adaptation to changing growing conditions.

Fermanagh occurrence

V. anagallis-aquatica has been recorded in just 72 tetrads in the VC, 13.6% of the Fermanagh total, as opposed to over 73.9% for V. beccabunga (Brooklime). Six tetrads contain only pre-1976 V. anagallis-aquatica records. The Fermanagh distribution of V. anagallis-aquatica is also peculiar in that it is quite frequently found around Lough Erne, but it is scattered and very local to rare elsewhere in the county.

British and Irish occurrence

Apart from tolerating a greater range of water depth than V. beccabunga, it is not obvious why V. anagallis-aquatica and the closely related V. catenata should be so much less common than Brooklime in a wetland county like Fermanagh where there would appear to be a wide range of suitable sites for all three species. Study of the hectad distribution maps of these three species and the Water-speedwell hybrid in Preston & Croft (1997) and in the New Atlas, however, shows that only V. beccabunga is evenly distributed over the whole of B & I (with the exception of the Scottish Highlands and the far NW, where it is scarce or absent). The other two Water-speedwell species are much more frequent in the climatically most continental portion of Britain that lies south of the familiar line from the Humber to the Severn and they really are only very local elsewhere in both B & I. This suggests a large-scale climatic factor is affecting the relative success of these two aquatic Veronica species. Although the distribution of V. anagallis-aquatica, measured at the hectad level, appears stable, Burnett (1997) is certain that there has been an appreciable decline in abundance of the species in England over a period of around 20-30 years towards the end of the 20th century.

European and world occurrence

V. anagallis-aquatica belongs to the Eurasian southern-temperate phytogeographical element and is a native of the temperate and Mediterranean regions of Europe, adjacent Asia and N Africa, extending from Iceland and central Scandinavia into C Siberia and almost entirely around the Mediterranean. It also discontinuously spreads eastwards from Turkey to N India.

The population in SE Asia is distinguished by some as subsp. divaricata Krösche, which has lax, usually glandular-pubescent racemes and arcuate-ascending pedicels (Hultén & Fries 1986, Map 1650). However, variants like this also occur locally throughout the range of the species and do not therefore merit subspecific distinction (S.M. Walters & D.A. Webb, in: Tutin et al. 1978, p. 248).

The species has also been introduced in N & S America, C & S Africa and New Zealand (Hultén & Fries 1986, Map 1650).

Names

The Latinised specific epithet 'anagallis-aquatica' of this plant previously was just 'anagallis', which at least as a genus name, was a label in Dioscorides, probably derived from two Greek roots meaning 'without' and 'boast', referring to an unpretentious plant (Gilbert-Carter 1964). An alternative derivation is from the Greek 'anagalao', meaning 'to laugh', the genus Anagallis being fabled to have the power to remove sadness (Chicheley Plowden 1972; Hyam & Pankhurst 1995). However, this does nothing to explain how the name 'anagallis-aquatica' evolved and became a label for this aquatic plant, and the current author (RSF) is at a loss as to how to take the quest further.

Threats

None.

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