Primula Culture and Production

The name Primula or primrose is derived from the word primary or first, referring to the early growth and flowering in spring (Liberty Hyde Bailey Hortorium, 1976). More than 400 species of primula exist in the family Primulaceae (Griffiths, 1994). Other important horticultural genera in this family, besides primula, include pimpernel (Anagallis), rock jasmine (Androsace), persian violet, alpine violet or sowbread (Cyclamen), shooting star or american cowslip (Dodecatheon) and loosestrife (Lysimachia). The genus Primula consists of relatively shortlived perennial herbs with leaves arranged in basal rosettes. The flowers are usually five lobed and solitary in axils or arranged in stalked racemes, umbels or whorls (Griffiths, 1994; Liberty Hyde Bailey Hortorium, 1976). Primula originates from the northern hemisphere, China, Europe and the Mediterranean (Griffiths, 1994; Liberty Hyde Bailey Hortorium, 1976; Ward, 1997). Several primula species are produced and used as bedding plants or flowering potted plants (Table 1). The most important species in production include english primrose or acaulis primula (Primula vulgaris synonym P. acaulis) (Blom et al., 1987; Coombes, 1985; Griffiths, 1994), polyanthus, polyantha primrose or hybrid primrose (P. ×polyantha), fairy primrose or baby primrose (P. malacoides), german primrose or poison primrose (P. obconica) and cowslip (P. veris). Chinese primrose (P. sinensis) is also produced in limited numbers and some interest exists in producing drumstick primrose (P. denticulata) as a container plant. Primula is widely produced in Europe as a flowering potted plant for the late winter and early spring market. In the United States, the growing conditions in the Pacific Northwest are particularly well suited for producing primula. In addition to flowering potted plants, primula is used together with other plants in potted arrangements, color bowls and hanging baskets or as a potted plant for outdoor planting in areas with moderate summer temperatures (Goldsberry, 1980). In recent years, sales in the United States have been primarily of bedding plants in areas with mild winters or early spring elsewhere. For garden and bedding uses, english primrose and polyanthus are considered hardy to zone five (Dole and Wilkins, 1999) while fairy primrose, german primrose and chinese primrose cannot withstand frost (Table 1) (Brickell and Zuk, 1996; Karlsson, 1997). Many commercial interests and gardeners are involved in breeding, propagating and growing the numerous primula species and hybrids. Species that are more appropriate for garden plantings include garden auricula (P. ×pubescens, a cross between P. auricula and P. hirsuta), cowslip, julian primrose (P. juliae), siebold primrose (P. sieboldii), and redleaf primrose (P. rosea) (Dole and Wilkins, 1999).