Primula vulgaris Huds., Primrose
Account Summary
Native, common. European temperate.
1858; Brenan, Rev S.A.; by Ardunshin Bridge on the Colebrooke River.
Throughout the year.
Growth form and preferred habitats
Primrose is an extremely common and widespread rhizomatous, rosette-forming perennial throughout B & I, typically frequenting woods, scrub, hedgerows, grassy wayside banks and damp moderately acid to alkaline, preferably lime-rich pastures. It is, however, principally absent from four types of soil and habitats: regularly flooded ground; deep, strongly acid peat; shallow, dry ranker soils formed over hard crystalline limestone; and very light strongly acidic soils, particularly where these are likely to dry out in summer (Richards 1989, 1993).
Under the often cloudy, overcast skies of the most western regions of B & I, shade-tolerant and hot sun avoiding perennials like Primrose and Hyacinthoides non-scripta (Bluebell) are not confined to woodland canopy or to north-facing cliffs and slopes as they generally are in drier parts of SE England with a more continental-style of climate. Rather here, in the western edge of the British Isles, these spring-active vernal herbs frequent mesic pastures, hedge banks, wayside embankments and verges that offer similar moderate levels of soil moisture, fertility and reaction, but which are completely unshaded (Whale 1984). In well-lit yet humid grasslands of these types, the wrinkled, evergreen leaf rosettes of P. vulgaris and their familiar luminous, buttery yellow, long-lasting flowers are especially plentiful and conspicuous on the steeper grassy banks, quite irrespective of their aspect. The ecological strategy of established plants was summarised and described as S/CSR by Grime et al. (1988), meaning P. vulgaris has life strategy characteristics that lie intermediate between a stress tolerator and a balance of competitor, stress-tolerator and ruderal species.
Fermanagh occurrence
This familiar perennial is very common and widespread throughout Fermanagh in all kinds of damp grassland and in woods, scrub and other shaded habitats. It is the 19th most frequently recorded vascular plant in the county and has been recorded in 456 tetrads, 86.4% of those in the VC. While almost ubiquitous, P. vulgaris is most noticeably absent from the blanket bog area to the north of Upper Lough Macnean and around Little Dog and Big Dog, where deeper peat and extensive conifer plantations exist.
Herbivory and possible toxicity
On steep sites, Primroses encounter reduced grazing pressure from both stock animals and smaller herbivores, especially rabbits, the animals being discouraged by gradient and gravity. The current author (RSF) has observed that horses leave perfectly accessible Primrose clumps and their leaves and flowers completely alone, even when the accompanying vegetation has become very well-grazed, indeed almost entirely depleted. In coastal Wales, Knight (1998b) noticed that rabbits consumed only the flowers and appeared to find the leaves unpalatable. Slugs and snails are also fond of Primrose, nibbling leaves and flowers, often to destruction.
Flowering reproduction
The large, tubular, pale yellow flowers have their parts in fives and are usually borne on separate, long, hairy stalks (pedicels) arising from the base of the plant. Flowers rarely appear either white or reddish-pink. A rare variant that bears an umbel of flowers on long, hairy pedicels attached to a scape (leafless stem), called forma caulescens (W.D.J. Koch) Schinz & Thell, sometimes occurs singly amongst normal forma vulgaris flowering plants (Sell & Murrell 2014).
Plants usually flower from early March into May or early June and are well known to be of two types in roughly equal numbers, 'pin' (long style) and 'thrum' (short style), clearly differing in the length of the female style and the relative positions of the anthers and stigma. This heteromorphism (or heterostyly) is an apparently simple, but actually rather complex, genetic mechanism designed to achieve a high degree of cross-pollination by means of an insect visitor inserting its elongated proboscis mouthparts (often erroneously referred to as its 'tongue') into the tubular blossoms to reach for nectar secreted at the base of the ovary (Richards 1989). Pin flowers can also occasionally self-pollinate, but thrum flowers never do, the thrum pollen tube failing to penetrate its own style (Richards 1989, 1993). In either case, seed is rarely set in the absence of cross-pollination (Richards 1989).
Many flowers contain sheltering thrips and small beetles, but these rarely carry pollen between flowers. Pollen transfer is carried out by insect visitors with long proboscis mouthparts, such as hive bees, bumblebees, butterflies and moths. Seed is rarely set without cross-pollination. All the flowers on a single plant are of the same type, the heterostyly character being under genetic control (Richards 1989). Experimental emasculation experiments that removed the anthers while still in the bud proved that heterostyly does promote pollen travel between pins and thrums, so that more pin pollen is found on thrum flower stigmas and thrum pollen on pin stigmas, than would be expected by random cross-pollination. Thus Charles Darwin was probably correct that the reciprocal positioning of the anthers and stigma in pin and thrum flowers helps pollen to travel legitimately to the stigmas of the other flower type, where it can successfully carry out cross-fertilisation (Richards 1989).
Seed dispersal
The very commonness of P. vulgaris and its widespread distribution in B & I is rather odd when one recognises that the seedling is slow-growing, making establishment more hazardous, and the species is low-growing, rendering seed dispersal by wind difficult or unlikely. Ripe seeds are dark brown, irregularly shaped and about 1.5 mm in diameter. There is no specialized release mechanism: they simply drop out of the weak-stemmed capsule which typically flops to the ground in summer, only reaching a few centimetres from the parent leaf rosette (Knight 1960). However, the resultant small pile of seeds attracts ants, since the seed-coat has an attached nutritive elaiosome oil-body, rich in fatty acids and similar in type to that of Viola odorata (Sweet Violet). Ants avidly collect and transport the seed and its sticky attached reward towards their nests. Many Primrose seeds will no doubt end up buried in ant nests, but some are simply dropped en route and others have their oil-body bitten off and are discarded outside the nest, some distance from their site of origin (Ridley 1930, pp. 520-1).
Study on the activity of European ants by Sernander (1906) quoted by Ridley (1930) indicated seeds of various types being transported distances from 15 to 70 m and although this did not specifically involve Primrose seeds, it gives some idea of the possible effectiveness of the mechanism. On the other hand, possession of a nutritive seed appendage can increase their depredation and destruction. Crosby (1966) found that seed capsules of P. vulgaris were heavily predated by mice, voles and slugs. Seedlings of the plant are also sometimes found outside the burrows of voles and mice and these mammals may inadvertently assist Primrose dispersal by attempting to store surplus capsules for their own further use (Richards 1989). It would be interesting to know if any further work on this rather involved topic has been completed, since it has implications for other common woodland species including Viola spp.
Despite the observation quoted above that horses avoided grazing P. vulgaris, viable seed has been recovered from the faeces of both horses and cows, indicating that at least the fruit capsules are grazed and seed is internally transported (Ridley 1930, pp. 360-1).
The dispersal pattern of P. vulgaris appears to differ from other British Primula species, plants occurring either as relatively distant individuals or clumped in clones, rather than more randomly distributed. Richards (1989) commented that the sites to which ants and rodents carry the seeds may prove relatively favourable for seedling establishment.
Regeneration from seed
The regeneration strategy of P. vulgaris involves the survival of buried seed, either short-term (1 to 5 years), or long-term (longer than 5 years) (Thompson et al. 1997) and their eventual germination and establishment after some form of disturbance bringing them back to the soil surface in an ecologically suitable environment. Seedlings are seldom found in sites occupied by other plants or where there is an accumulation of leaf litter. Most frequently they are found on ridges, sloping banks, disturbed ground and other bare earth sites, usually close to the parent plant (Knight 1960).
Weakening effect of drought
P. vulgaris is so very common and widespread in these islands, it is really absent only from peaty and/or heavily waterlogged situations and from very light, strongly acidic soils, particularly where these are likely to dry up in summer (Richards 1989, 1993). The latter observation is all the more surprising since the plant does possess a sturdy, often near-vertical rootstock, which might be considered an adaptation allowing the species considerable drought resistance. It is a common observation that even severely wilted leaf rosettes whenever they are rewetted generally revive remarkably quickly and, to the naked eye, they appear completely undamaged. Obviously drought survival depends upon the degree and duration of water depletion and any amount of wilting may physiologically weaken the individual plant, leaving it more vulnerable to competition from neighbours, less able to respond to depredations by vertebrate and invertebrate herbivores and, most likely of all, susceptible to attacks by disease organisms. All Primula species are vulnerable to an aphid-dispersed Cucumber mosaic virus, to a Botrytis root rot and, as gardeners know to their cost, slugs can also do devastating damage to both leaves and flowers overnight.
British and Irish occurrence
P. vulgaris is widespread throughout B & I, still locally abundant in many parts, but in numerous other areas it has declined, becoming local and scarce. The reasons for this are not well documented, but in SE England the decline may be due to a sequence of dry summers (Rackham 1999) and, in all urban areas throughout the land, decline may be due to centuries of collecting for horticulture (Richards 1993).
Conservation
In Britain, Primrose is protected by a law passed in 1975 and in NI protection was given under the Wildlife (NI) Order 1985, in being listed on Schedule 8 Part 2 which allows the flowers to be picked, but the plant must not be uprooted.
European and world occurrence
P. vulgaris is a polymorphic species with three subspecies in Europe (subsp. balearica (flowers white and very fragrant, an endemic, confined to the mountains of Mallorca), subsp. vulgaris and subsp. sibthorpii (flowers usually red or purple, confined to the E part of the Balkan peninsula, Krym (in the Black Sea), Turkey, Iran and locally naturalised in C Europe) (Flora Europaea 3, Tutin et al. 1972)). Richards (1993) recognises a fourth subspecies, subsp. heterochroma (Stapf) Smith & Forrest loc. cit., which has flowers violet, purple, red, pink, white or yellow and occurs on the S shore of the Caspian Sea (Elburz Mountains), Iran and Azerbaijan, in a disjunct area.
The plant that occurs in B & I is subsp. vulgaris, which belongs to the European temperate element and occurs in W, SC & S Europe, extending to Denmark and N Ukraine. It also stretches to adjacent parts of N Africa and Asia (Hultén & Fries 1986, Map 1465).
Hybrids
P. vulgaris forms hybrids with both P. veris (Cowslip) and P. elatior (Oxlip) in the wild in Britain but, as the latter does not occur in Ireland, only the cross with Cowslip is relevant here and it is very rare in Co Fermanagh (see the separate account).
Cultivated forms
Unlike its relatives, the primrose has given rise to a vast range of cultivated variants quite apart from its hybrids (Richards 1993). Cultivated varieties of P. vulgaris include mutant forms with double, semi-double, 'hose-in-hose' (petaloid calyx), 'Jack in the green' (leaf-like calyx) and numerous colour breaks such as gold- and silver-laced petals and a wide range of colours. (Richards 1993; Griffiths 1994). Old plants are susceptible to virus, root-aphis and weevils and clones can therefore be difficult to keep in the garden setting. Plants are most successful when they seed around and successfully self-sow.
Medicinal use and folklore
Since P. vulgaris is a lot more common and widespread in comparison with P. veris, Primrose has been put to much more use in traditional herbal medicine than Cowslip. In England, Primrose leaves have been made into an ointment to heal cuts, bruises and chapped hands or chilblains, or combined with bramble tops to clear up spots and sores on the face. The ointment was made with pork lard and primrose leaves, or else the rootstock was used with beef or mutton suet (Vickery 1995). The ointment has also been smeared on ringworm and the leaves have also been applied (presumably as a poultice) to treat boils (Allen & Hatfield 2004). Primrose was also regarded as a suitable cure for yellow jaundice, the roots being boiled in water and a wine glass of the resultant fluid drunk each morning (Vickery 1995). The plant is also regarded as a relaxant and sedative in some parts of these islands, being used as a tea for a wide range of complaints including muscular rheumatism, paralysis, gout, insomnia, nervous hysteria and headaches. The whole plant has also been used as an expectorant (Grieve 1931).
In folklore, Primroses were often associated with poultry keeping, less than 13 flowers brought into a house on the first occasion of doing so in the year, being unlucky and limiting the fertility and egg hatching ability of hens and geese for the season to the number of flowers collected. Thirteen was the traditional number of a clutch of eggs placed under a 'clucking' hen during the spring to hatch, each yellow primrose therefore being the analogue of a young chick that would eventually emerge from the egg (Vickery 1995). A similar belief on farms in Ireland was that throwing a primrose into the byre door on May Day prevented the fairies from taking away the milk from the cows for the year (Vickery 1995).
Names
The Latin genus name 'Primula' is the feminine of 'primulus' the diminutive of 'primus', meaning 'first' and refers to the idea that this is the first (or one of the first) flowers of spring (Gilbert-Carter 1964). The English common name 'Primrose' refers to the first (prime) rose of spring, again referring to the early flowering of the species.
Threats
Habitat destruction and collecting for horticulture.