Primula (Primrose)

Primula

A large group of related plant species, containing annuals, biennials and perennials. All are grown for their bright and cheerful spring flowers, ranging from border primroses and alpine plants to tender species for indoor displays.

Family: Primulaceae
Botanical Name: Primula
Common Names: Primrose, Polyanthus, Auricula, Cowslip

Foliage: Evergreen to semi-evergreen, rosettes of bright-green simple leaves.

Flowers: Clusters of five-petalled solitary flowers, available in a wide range of colours and forms, depending on variety. Single, double or semi-double forms are available. Yellow coloured forms are particularly fragrant.

Flowering Period: Spring.

Soil: Moist, humus rich fertile soil. Chalk, clay, sand or loam. Any pH.

Conditions: Sun or partial shade. Plant in any aspect, in a sheltered possition.


Habit
: Spreading, clump forming.

Type: Herbaceous or semi-evergreen perennials.

Origin: Western and southern Europe and Northern Hemisphere.

Hardiness: Hardiness ranges from fully hardy to frost tender. Many of the modern hybrids are not as frost hardy as the wild species.

Planting and Growing Primulas

There are several distinct types of primula:

  • Primula variabilis/polyantha: (polyanthus) available in a wide range of colours. Ideal for flower beds, containers or front/back of the border.
  • Primula vulgaris: (primrose) ideal for borders, containers or natural/wildlife gardens.
  • Primula auricula: alpine plants that prefer a sunny position in free draining soil.
  • Primula florindae and veris: (cowslip) moisture-loving plants that prefer deep, fertile, moisture-laden soils.

Most forms are easy to grow apart from auriculas (see growing guide below). Nearly all polyanthus and primroses thrive in partial shade and prefer a fertile humus rich soil. These make very attractive spring bedding plants, in spring containers or as the edging to a shady bed. Candelabra forms prefer dappled shade.

Plant out between autumn and spring in a sheltered position, in any good garden soil, in sun or partial shade. Add plenty of leaf mould and humus at planting time and water well until established. Polyanthus will even do well in heavy clay soils, provided they are not waterlogged in winter.

Many varieties make ideal short term house plants, which can be successfully grown indoors. Once flowering has finished they can be planted out in the garden.

Growing Auriculas

Species auriculas will grow outside but hybrid show auriculas are best grown under glass, in an alpine house or cool greenhouse. Although primula auricula is a hardy species from the alpine regions of Europe, they don't tolerate wet British winters well, so are best grown under glass without heat. Give them maximum light in winter but shade from direct sun. They also prefer plenty of ventilation and a sharp well-drained gritty soil that contains plenty of organic matter.

The best growing medium is clay pots filled with a loam-based potting compost such as John Innes No 2, with a little extra grit or sharp sand to ensure adequate drainage. Feed weekly during the growing season and water well from the base. Keep the compost just moist throughout the winter months.

Taking Care of Primulas

Mulch outdoor grown plants in early spring and water well in summer. Give houseplants a cool light position such as a north or west facing window.

Most primulas bloom in spring, providing a much needed early splash of colour. They dislike hot dry conditions, so tend to hibernate during the summer, only to awake again during the moister conditions of early autumn. For this reason they are often grown as annuals and discarded after flowering, especially if grown in a sunny border.

Pruning Primula

Deadhead to encourage a second flush of flowers and prevent self-seeding.

Pests and Diseases

Susceptible to attack by aphids, caterpillars, weevils, cutworms and slugs.

Susceptible to fungal, viral and bacterial diseases, soft rots, grey mould and leaf spot.

Birds may attack blooms in winter and spring. Deter them with a network of black thread, stretched over the bed between short sticks.

Propagating Primulas

All primulas species except named cultivars should come true from seed. Seeds should be sown as soon as they are ripe, around late spring to early autumn. Do not cover the seeds with compost as they need light to germinate. Cover pots or trays with clear glass (or clear plastic tray covers) to conserve moisture until germination. The temperature should not exceed 15 deg C. Shade seedlings from direct sunlight and keep moist. Prick out seedlings into individual pots or modules when they are large enough to handle and grow them on in a cold frame. Ventilate well in warm weather. Plant out in from early to mid autumn. Water well and protect from slugs and snails.

Named cultivars can either be divided in spring or cuttings taken in the summer.

Popular Varieties of Primula Grown in the UK

Over 500 species of Primula have been discovered, mainly from temperate regions of the Northern Hemisphere. Due to extensive cross breeding and cultivation almost every colour is available, in pastel shades, vivid hues, bicolours and even tricolours, all with a bright yellow center.

Primula Auricula is a perennial alpine species producing delicate fragrant flowers in April-May. Average height 6in (15cm), spread 8in (20cm).

Candelabra Primulas are identifiable from their tall spikes of tiered flowers, which appear from late spring to early summer. They originate from the Himalayas and are the tallest garden primula species. These hardy perennials thrive in any fertile garden soil, that retains moisture in both spring and summer. Ideal for a pond, bog garden or growing alongside streams. They can also be grown in bedding displays if the soil is damp. Average height 2ft (60cm, spread 1ft (30cm). Good varieties include: Primula beesiana with whorls of rose-carmine flowers in June. Primula bulleyana with orange flowers in June-early July. Primula japonica one of the earliest candelabra forms to bloom.

Primula denticulata (drumstick primula) are a group of hardy perennials that prefer dappled shade or a woodland setting. They produce large globular flower heads in March-May, followed by large green leaves. A range of varieties are available with flowers in white, purple or lilac. Average height and spread to 1ft (30cm).

Primula florindae (giant Himalayan cowslip) has large pendent, bell-shaped, yellow flowers in dense clusters on reddish stalks, in June-July. One of few species to grow in shallow water. Flowers available in shades of yellow, orange, pink and brown. Height 3ft (90cm), spread 2ft (60cm).

Primula Polyanthus are hybrids of the native primrose and cowslip. They are bigger and brighter than the common primrose, with rosettes of bright green leaves and flowers in a wide range of colours, from March to May. Height and spread up to 1ft (30cm).

Primula Sikkimensis (Himalayas, Burma, Yunnan) are a group of hardy perennial primulas with clusters of showy yellow bell-shaped flowers, on stout stems in May-June. Height 2ft (60cm), spread 1.5ft (45cm).

Primula veris (cowslip) is a moisture loving hardy perennial with deep yellow, fragrant flowers in April-May. Height and spread 6-8in (15-20cm).

Primula vialii are a small group of primulas with distinctive flower spires of red tipped lilac-pink on thick stems over compact deeply-veined, lance-shaped leaves.

Primula vulgaris (common primrose) is group of hardy perennials that provide clusters of ovate, green leaves topped with bright flowers from March to May. Available in a wide range of colours. Height to 6in (15cm), spread to 8in (20cm).