Primula vulgaris, a popular sign of the advent of spring in the British Isles, is native to Europe, western Asia and parts of North Africa. Primroses are found in patches of grassland, woodland glades and along field and woodland margins and roadside verges. The name 'primrose' ('first rose'), derived from Old French and Medieval Latin, is an allusion to the plant's appearance in early spring.
The primrose should not to be confused with Primula veris (common cowslip). When grown together the differences between the two species are obvious. The cowslip has deep-yellow flowers, borne on tall, erect flower stalks. In contrast, the primrose typically has pale yellow flowers on short flower stalks. Flower colour in primroses can be highly variable, with colours ranging from yellow through cream to pink, which is one reason they are so attractive to gardeners. One of the pink-flowered sorts, Primula vulgaris ssp. sibthorpii, is found in the eastern Mediterranean; it commemorates the Oxford academic, John Sibthorp, who collected plants in the region at the end of the eighteenth century.
Radially symmetrical, hermaphrodite primrose flowers produce capsular fruits that open by valves to release small, black seeds. Individual primrose plants produce one of two types of flower: pin flowers with long styles; and thrum flowers with short styles. Effective fertilization only happens between pin and thrum flowers, and vice versa. That is, individual plants cannot produce seed through selfing; cross-fertilisation must happen.
Primula vulgaris was growing in the Oxford Botanic Garden in 1648. The Catalogue includes blue, white, yellow and purple sorts, plus white doubles, whilst herbarium specimens also show a diverse array of other floral mutants in cultivation. At this time, primroses were considered effective remedies for muscular rheumatism, paralysis and gout; Pliny regarded them as a virtual panacea.
The primrose, which became fashionable during the Elizabethan era, has enjoyed frequent waves of popularity among gardeners. Plant breeders have selected new cultivars, although many of these are sterile; they can only be propagated by division. Despite many original cultivars have been lost some are being bred once again and re-introduced, such as Primula 'Gold Lace' (as part of winter garden displays). During the eighteenth century, primroses started to be crossed with other Primula species to produce complex hybrids, which we now call polyanthus. There seems to be no limit to the polychrome palette of polyanthus, which are used as cheerful bedding during the winter months.
Endels P et al. 2002. Temporal changes (1986-1999) in populations of primrose (Primula vulgaris Huds.) in an agricultural landscape and implications for conservation. Biological Conservation 105: 11-25.
Gilmartin PM 2015. On the origins of observations of heterostyly in Primula. New Phytologist 208: 39-51.
Jacquemyn H et al. 2009. Biological Flora of the British Isles: Primula vulgaris Huds. (P. acaulis (L.) Hill). Journal of Ecology 97: 812-833.