Parietaria judaica L., Pellitory-of-the-wall
Account Summary
Very probably introduced and locally very rare. Submediterranean-subatlantic, but also present in C Asia.
1934; Praeger, R.Ll.; old wall in Enniskillen Town.
Growth form and preferred habitats
This easily recognised small to medium sized perennial is common elsewhere in Ireland, especially in the far south and around Dublin and the Wicklow area. A lowland species, it grows mainly on old walls, but occasionally on coastal rocks and shingle beaches. It generally prefers dry, sunny, relatively sheltered situations. Under suitable growing conditions this stress-tolerant species can become both frequent and abundant and clearly demonstrates pronounced competitive ability. It has a short, woody rootstock and is reputed to have long, slender, but tough roots that worm their way deeply into mortar or down into shingle or rock crevices looking for moisture, thus providing the plant with strong anchorage. The reddish stems are annual. They are either erect or prostrate, and bear alternate, downy leaves that taper at both ends. In urban areas of Britain and Ireland the species typically grows in tufts out of cracks in walls or in the mortar between stones or bricks. The numerous silky, stingless hairs on the plant tend to become covered with air-borne dust, usually derived from nearby roadways.
Flowering
From June to September the small, simplified flowers are produced in tight, greenish cymose clusters in the axils of leaves, especially towards the top of the red stem. The perianths of the flowers become reddish in fruit. The flowers are mostly unisexual, but sometimes they are intermingled with a few bisexual ones. The female flowers are terminal and the males lateral (Clapham et al. 1987). In either event, unisexual or not, the flowers are wind-pollinated (Melderis & Bangerter 1955). The fruit is a smooth, shiny, black, ovoid achene (ie a single seeded dry fruit), sometimes referred to as a nut. It is truncate (ie flattened at one end), measures 1.5 × 1.0 mm and is enclosed by the reddish brown persistent calyx segments (Butcher 1961).
Fruit dispersal
As described, the achene or nut fruit has no obvious adaptation enabling or assisting dispersal, except it is small in size and light in weight. Undoubtedly it is to some extent wind dispersed, but as noted above, the plant typically prefers relatively sheltered growth sites. Having said this, Ridley (1930, p. 29) includes Parietaria (as P. officinalis), ranking it last (and therefore possessing the least obvious means of transport) among a long list of species recorded by O.J. Richard in 1888, observed high up on the walls and towers of churches in Poitiers, France. The plants listed were all recorded at heights on the walls of the studied buildings, in sites above any buttresses and porches. One can therefore assume the sites were exposed to wind. P. judaica is commonly recorded in similar elevated sites throughout Britain and Ireland and, again, wind appears the most probable means of seed transport.
The achenes of some Parietaria species appear to be attractive to ants and have been found in their nests. They include P. lusitanica, the fruit of which is reported to have a small swelling at its base acting as an eliasome or food body reward for the ant vector, and P. diffusa (= P. judaica) which does not appear to possess a food body, yet has also appeared in ant nests (Ridley 1930, pp. 520-4). This is not considered a likely dispersal mechanism for P. judaica in most wall or cliff environments.
Fermanagh and N Ireland occurrence and status
Strangely, until 2011 P. judaica was considered virtually absent and about to become declared extinct in Fermanagh, having previously been seen only once, in Enniskillen in 1934 by Praeger (1934c). Then, in June 2011, Robert & Hannah Northridge rediscovered a well-established colony on the walls of Monea Castle, a National Heritage site. Since then it has been found again by the Northridges in a garden at Killyreagh House near Tamlaght in 2014 and 2015.
Paul Hackney in FNEI 3 concluded that P. judaica is almost certainly not native in the NE of Ireland. He decided this on the basis that almost all of its occurrences were on the mortar of old walls, it was unknown on natural rock outcrops, and the single coastal shingle record in Co Down was probably a secondary habitat.
Beesley & Wilde's survey of the flora of urban Belfast located the species in seven 1-km squares around the city. They described the occurrence of the plant as being, "occasional on old walls", although they also recorded it on waste ground in the city, and they regarded its status as introduced and naturalised (Flora of Urban Belfast). Thus Pellitory-of-the-wall is scarce or rare in NI, having recent records in only 15 hectads, most of which are either coastal, around Lough Neagh, or confined to old walls in the larger towns (NI Vascular Plant Database).
Republic of Ireland and British occurrence and status
The New Atlas map shows the species concentrated in the S and E in both Ireland and Great Britain, becoming rarer and more restricted to coastal sites in E Scotland as one travels northwards, indicating a well-marked climatic limitation on its distribution. The species does, however, extend very much further north in Britain than in Ireland in terms of latitude (Preston et al. 2002). It is not obvious why it is so scarce in the N of Ireland and in Fermanagh in particular, but clearly we have a puzzle here which could repay further investigation.
Praeger commented that the species appears "unquestionably native in the Central Plain and the South [of Ireland]" (text in square brackets is my addition to clarify Praeger's view) (Praeger & Megaw 1938). The New Atlas hectad map plots the vast majority of P. judaica records in Britain & Ireland as being native, including all of the Irish records. An Irish Flora (1977, 1996, 2012) and the Cen Cat Fl Ir 2 also fail to discriminate between the status of northern and southern occurrences of P. judaica, treating them all as native.
In relation to the status question and also the species known distribution, it is significant that Pellitory-of-the-wall (previously known as P. officinalis L.), has had a long history of use in herbal medicine for the treatment of urinary complaints. It was certainly cultivated by medieval monks in their physic gardens, and very probably this happened throughout Britain & Ireland, and possibly much further afield, perhaps worldwide (Grieve 1931; Harvey 1981; Darwin 1996). It is therefore unsurprising that it would be transported by man and introduced to regions well beyond its native occurrence. For instance, both P. judaica (commonly) and P. officinalis (two sites only) have been reported as introductions in New Zealand (Webb et al. 1988), and also in N America.
European and world occurrence
P. judaica is native and widespread in most of W Europe the Mediterranean region. It is also recorded in Macaronesia (Madeira and associated islands), very possibly a western outlier where I suggest it might have been introduced as a medicinal plant (Townsend 1968; Press & Short 1994). As the species name suggests, it is also known from SW Asia, including a quite remote eastern outlier at Tian Shan in S China, together with Pakistan, Iran, Iraq, Syria, Palestine, Lebanon, Egypt and NW Africa (Townsend 1968). As noted above, P. judaica is certainly introduced very widely around the globe, including the southern hemisphere.
Medicinal uses
Pellitory-of-the-wall was regarded by herbalists as a most useful remedy for stones in the bladder, gravel, dropsy, stricture and other urinary complaints. It was given as an infusion of the plant (1 ounce to 1 pint of boiling water), and taken in wineglassful doses (Grieve 1931, p. 624). Gerard's Herball listed several other medicinal uses, including cleansing the skin from spots, freckles, wheals and sunburn (Gerard 1633).
Names
The genus name 'Parietaria', is derived from the Latin 'paries', meaning 'a wall' or 'a house-wall', into which this weedy plant often grows (Prior 1879). The specific epithet 'judaica' means 'of Judaea', and the previous and perhaps more familiar epithet, 'diffusa', is Latin meaning 'spreading', or 'loosely spreading' (Gilbert-Carter 1964).
The English common name 'Pellitory-' or 'Paritory-of-the-wall' was so named to distinguish it from the original 'Pellitory', 'Pellitory-of-Spain', the composite Anacyclus pyrethrum of SE Europe. The name 'Pellitory' is derived from 14th century Old French 'peletre' or 'piretre', from the Latin 'pyrethrum', from Greek 'purethron', which comes from 'puretos' meaning 'fever'. In the 14th century Parietaria diffusa (= P. judaica) was known by the Old French name 'Paritarie', from the Latin already detailed above, and similarity of sound combined the two plant names into 'Pellitory', which then had to be distinguished from one another by habitat and geography (Grigson 1974).
Threats
None.