Polygala vulgaris L., Common Milkwort
Account Summary
Native, frequent. European temperate.
1882; Stewart, S.A.; Co Fermanagh.
March to January.
Growth form and preferred habitats
A small perennial with a short, tufted, somewhat woody basal rootstock that sends up many branches, P. vulgaris is a rather variable, low-growing, ± hairless species with stems 7-35 cm, ascending to erect but very often sprawling, branched and leafy. The stalk-less, leathery leaves are all alternate on the stem, measure up to 35 mm long (the uppermost the largest), lanceolate-elliptic in shape and have entire margins. The irregular flowers of complex structure are borne in slender racemes, the largest of which contain 10-30 flowers. The flowers also vary greatly in colour, ranging from purplish-blue, lilac, pink to white, but never the clear dark blue that is so typical of P. serpyllifolia (McCallum Webster 1978; Sell & Murrell 2009; Parnell & Curtis 2012).
P. vulgaris is a species of short, dry, sunny, semi-natural, calcareous grassland. Typical habitats include pastures, cliffs and rock outcrops (some with a covering of open scrub), plus limestone pavement, stabilized scree, drier parts of lakeshores, alkaline to neutral fens, wayside verges and, much more rarely, on waste ground. The range of places where it can occur suggest it has some degree of shade tolerance. The requirements of the species are met chiefly on somewhat leached, unproductive, calcareous soils, while in base-rich regions in other parts of B & I the plant tolerates a pH range between 5.0 and 8.0, ie mildly acid to alkaline, avoiding the most acidic soils (Grime et al. 1988, 2007).
Flowering reproduction
Although P. vulgaris often produces numerous radiating prostrate branches from a central woody rootstock, these do not root, so that species reproduction is entirely by seed.
P. vulgaris flowers from May to September, with the main flush occurring in the first three months. The inflorescence is a ± dense, slender, terminal raceme, usually only 10 cm tall, bearing 10-40 bisexual (perfect, hermaphrodite) very irregular (zygomorphic) flowers. The inflorescence elongates considerably when it reaches the fruiting stage. Floral parts vary in number: three of the five sepals are small and green, while the other two are large and petal-like, forming 'wings', although later they may persist around the fruit capsule and turn greenish; petals are three in number, 4-10 mm long, fused to form a tube with three lobes, of which the middle one is fringed at the tip; stamens are eight in number, the filaments fused below for more than half their length into an open tube adnate to the petals, separate above forming two sets of four, the anthers distinct and opening by pores; the ovary is superior, formed of two united carpels and the curving style is 1.0-1.5 times the length of the stigma, which is 2-lobed and spoon-shaped. Nectar is secreted.
Pollination
Not only is the flower structure complex, pollination is also a very intricate mechanism. Insects, mainly bees, are attracted to the flowers by the two large, petaloid sepals and they alight on the median, fimbriated petal that presents itself at the front of the flower as a landing platform. Folds on the upper side of this petal enclose the anthers and the spoon-shaped end of the style. Just behind this 'spoon' is the sticky, hook-like stigma; the anthers are exactly arranged so that when they dehisce the pollen falls into the terminal spoon. When an insect visitor probes for the nectar secreted at the base of the flower, it first touches the pollen in the spoon and then the stigma. However, it is not until the insect's proboscis has become stickily smeared from touching the stigma on the way in that any of the pollen will adhere to it. This means the pollen is only collected as the insect leaves the flower after receiving the nectar reward, this arrangement thus definitely favouring cross-pollination (Hickey & King 1981).
Self-pollination can also occur, however, at the early stages of anthesis (flowering), when the amount of pollen shed into the spoon of the style is so large that some of it may get pushed back onto the sticky stigma as an insect’s proboscis enters the flower. It may also take place in the absence of insect visitors as a fail-safe mechanism, as the stigma is able to bend down and touch against the pollen lying in the spoon (Hutchinson 1945, 1972; Hickey & King 1981).
Fruit and seed
The fruit capsule is 4.0-8.5 mm, ovate and laterally compressed and narrower than the inner sepals which partly conceal it. When ripe, the capsule bursts along its margins to release the two contained 3.0 × 1.0 mm, downy, ovoid seeds (Melderis & Bangerter 1955; Butcher 1961; Sell & Murrell 2009; Parnell & Curtis 2012). Each seed bears a relatively large, 2-lobed elaiosome oil food body (or caruncle), that attracts ants that help disperse them locally, thus minimising seed predation (Hickey & King 1981). The survey of NW Europe soil seed banks failed to discover seed persisting more than a single year (Thompson et al. 1997). Seed germinates in the spring (Grime et al. 1988, 2007).
Variation
P. vulgaris is the most common and ecologically wide-ranging species of the genus Polygala in Europe and, genetically, it is very variable. Five varieties of P. vulgaris are recognised by Sell & Murrell (2009) in their critical Flora of B & I: var. caespitosa Pers. is a grassland plant; var. intermedia Chodat is also a plant of grassland as well as of coastal situations; var. dunensis (Dumort.) Buchenau is a coastal sand-dune plant; var. ballii Nyman ex A. Benn. is a rare endemic form known only from the limestones of Ben Bulbin, Co Sligo (H28); and var. vulgaris is the most widespread variant on grassland, fens and river-banks, often, but not always, on chalk or limestone. All five of these B & I varieties belong to subsp. vulgaris (Sell & Murrell 2009).
Hybrids
Sterile, intermediate hybrids are known to occur extremely rarely in the genus Polygala and only three botanists have contributed all of the British records. There are just two hybrids featured in Stace et al. (2015): P. vulgaris × P. calcarata F.W. Schultz, for which twelve hectads in SE England have records in sites shared by both parent species, and even rarer, P. vulgaris × P. amarella Crantz, where there is a solitary British record from near Wye in E Kent (VC 15). No Polygala hybrid has ever been recorded anywhere in Ireland.
Fermanagh occurrence

In Fermanagh, this is a frequent and locally common, but never abundant, low-growing, often sprawling perennial of short, dry, calcareous grassland. P. vulgaris is recorded in 112 Fermanagh tetrads, representing 21.2% of those in the VC.
The very specific soil requirements and tolerances of P. vulgaris, together with the fact that all the leaves on the plant are alternate, including those on the lowermost portion of the stem, permits the safe distinction of this species from the closely related P. serpyllifolia (Heath Milkwort). Having said that, one other habitat situation where Common Milkwort can occur very locally is on wet acidic heaths where base-rich ground water springs flush the surface. This situation arises rather frequently in one particular area of Fermanagh – that around Monawilkin and the Correl Glen NR on the Western Plateau. In this rather unusual situation, the otherwise quite definite ecological barrier between the two most common Polygala species becomes lowered and here they may grow adjacent to one another.
British and Irish occurrence
Throughout the whole of B & I, P. vulgaris is still a locally frequent and widespread species, although it has decreased as a result of habitat losses during the last half century or more. It really can no longer be described as 'common' in B & I in comparison with previous years (M.J.Y. Foley, in: Preston et al. 2002). Many of the old, traditionally managed, relatively undisturbed, infertile, low-productivity pastures which provided a suitable habitat niche for this and other species of low competitive ability have been destroyed by post-1945 intensification of agriculture involving broad-spectrum herbicides and fertilizer sprays, or 'field improvements' that require drainage and ploughing of pastures and meadows, followed by reseeding. The several previously common forms of species-rich, calcareous grassland vegetation that supported P. vulgaris now only persist where ground is inaccessible for modern agricultural machinery which itself has greatly grown in scale in recent decades as manufacturers have produced larger, heavier and more powerful tractors. Examples of species-rich calcareous grassland vegetation are now rare and are confined to lake islands, or to small parcels of ground hemmed in by cliffs or water – only protected by being either too small, awkward or hazardous, or just too uneconomic for the farmer to work with.
Consequently, as with Linum catarcticum (Fairy Flax or Purging Flax) and other ecologically similar stress-tolerant species (Grime et al. 1988, 2007), P. vulgaris has suffered a decline in the available area of suitable habitat. Populations have been pushed to survive in rocky, steep, shallow or otherwise too difficult terrain for the farmer to manage. Alternative sites for these species also exists in artificial habitats such as derelict quarries and any neglected, under-managed ground that is subject to sufficient disturbance or other growth-limiting factors that reduce competition from taller, more vigorous species. Locally these less than ideal habitats include urban and village waste ground, churchyards and wayside verges of suitable base-status.
European and world occurrence
In phytogeographical terms, P. vulgaris belongs to the European temperate element and is widespread across most of Europe and also in W Asia and N Africa. The species map in Hultén & Fries (1986), Map 1288, shows it well represented throughout the Iberian & Italian peninsulas and eastwards into Greece. It is also present in Corsica, Sardinia and Sicily, but not in any other Mediterranean islands, although it is shown as occurring in the Azores.
Names and uses
The Latin genus name 'Polygala' is the name of an unknown plant taken to be the 'polygala' of Pliny and the 'polugalon' of the Roman medic Dioscorides from a combination of the Greek 'polus' and 'gala', meaning 'much milk', so called because it was supposed to increase the secretion of milk (Gilbert-Carter 1964). There is considerable doubt surrounding the application of the name to plants of the Polygala genus we know today, and whether infusion of the plant that improved milk flow was for human mothers or for cows in the field, since apparently Dioscorides did not make this clear. Herbalists took it to be for nursing mothers and prescribed it accordingly (Grigson 1955 & 1987). Allen & Hatfield (2004) cast considerable doubt on the whole hopeful identification of the Classical Polygala as this genus and any recognition of its milk inducing benefits, regarding the folklore credentials as highly questionable.
Another English common name for Polygala spp. from Waterford in S Ireland is 'Four sisters', an allusion to the four colours – white, pink, blue and purple – of flowers on different plants (Vickery 2019).
Eleven alternative English plant names, including 'Cross-flower', 'Rogation-flower', 'Procession-flower' and 'Gang-flower', are listed by Grigson (1955 & 1987), mostly so-called book names, associated with Rogation week processions that were once a regular feature of Christian church worship, when the plant was picked, made into garlands and carried around the parish when the bounds were beaten and crops blessed. In the procession, the parish Cross was carried and bells were rung. In England, the May blossoming of the plant must have usually been a little late for Rogation.
In Wales, P. vulgaris was named 'Llysiau Crist' ('Christ's herb'), no doubt from the same continental tradition of the Milkwort garlands and the associated junketing before Ascension Day. In Co Donegal, the plant was called 'Fairy Soap' from a local belief that fairies make a lather from the root and leaves (Grigson 1955, 1987).
On Guernsey, P. vulgaris was known as 'Herbe de paralysie' and was allegedly used to prevent or cure paralysis or stroke. The same local name was also applied to Potentilla erecta (Tormentil) (Vickery 1985).
Threats
The expansion of agricultural set-aside and other environment-friendly government funded farm subsidy schemes may allow species such as this to recolonize lost ground. Post-Brexit it remains to be seen what kind of farm support package(s) will be available and whether it will enable plant species like this one to retain and regain ground in suitable habitat.