Plant Guide: Crocus

There are more than 80 species of crocus, which mainly flower in winter and spring, although a small number flower in autumn. Crocuses are among the earliest spring flowers, and their blooms sometimes push up through snow. In some species the flowers appear a few weeks before the leaves. Most crocuses are native to the countries around the Mediterranean, where they usually grow at high altitude. Further east, they occur as far as Afghanistan.

Appearance Crocuses have short, fairly sparse, grass-like foliage. The attractive, cup-shaped flowers sit on short stems, 6–12 cm long. Most are blue, purple, white, yellow or creamy-white, but some species have pink flowers. In many species the petals have darker streaks or markings.

Use Although you can pick them, these small bulbs look their best in the garden. They are usually planted in large numbers in beds, especially at the front of borders. You can let them naturalise in grass or under deciduous trees. Crocuses are very well suited to rock gardens and look lovely in pots in early spring, especially in window boxes. Some species flower only briefly, but by planting a range of different species you can enjoy these cheerful flowers almost continuously from late autumn until late spring.

POPULAR TYPES

Spring Some of the most popular spring-flowering species are C. biflorus, C. chrysanthus, C. flavus, C. minimus, C. tommasinianus and C. vernus. Cultivars of several of these are available, with those of C. chrysanthus being especially popular, although every species has its own devotees. C. ancyrensis flowers particularly early, as soon as January–February.

Autumn Autumn-flowering species include C. kotschyanus, C. niveus, C. laevigatus, C. longiflorus, C. nudiflorus, C. sativus (the saffron crocus), C. serotinus (also known as C. salzmannii) and C. speciosus. Crocus sativus is known as the source of the world's most expensive spice. The saffron crocus, native to the temperate regions of Eurasia and widespread across the Mediterranean, needs a very particular climate to flower and is an extremely labour-intensive crop. Saffron comes solely from the stigmas of the flower, and 154,000 flowers are needed to produce a single kilogram.

GROWING CONDITIONS

Position Preferably a light, sunny spot that will also tolerate light shade.

Location Suited to rock gardens, raised beds, the front of borders, and naturalising in grass. Needs well-draining soil, ideally rich in humus.

GROWING

Planting Plant new corms about 5 cm deep and 5–10 cm apart. Species that flower in spring are planted in autumn — from September to November — while autumn-flowering species should be planted in July and August. The corms of some species can become fairly large over time; lift them and, if necessary, space them a bit further apart.

Feeding Apply some fertiliser after flowering, especially on poor soil. Watering is only needed during very dry spells; however, plants that flower in autumn should be kept moist through summer after planting.

Problems When crocuses are planted in a suitable spot and in the right soil, they cause few problems. Birds can occasionally damage the flowers. Sparrows in particular seem to be drawn to the shape or colour of the flower and can peck them to shreds. If this happens, you'll need to stretch netting over the plants.

FLOWERING

Season Flowering time depends on the species; some varieties flower from late winter into early spring, others a little later. Autumn-flowering species do so between September and early December, and their flowering sometimes overlaps with the earliest winter bloomers if these are growing against a warm wall.

Cutting Crocuses do not make good cut flowers, although they will last a few days in a vase.

AFTER FLOWERING

Care It is absolutely essential to leave the crocus foliage in place until it has turned completely yellow, since the corm needs to gather enough food to flower the following season. Every three to four years you can lift and divide the small corms, or you can simply wait for them to work their own way up to the surface.

AT A GLANCE

A low-growing bulb, highly valued for its early spring flowers in a range of colours. An excellent container plant.

Note: the table in the book uses symbols to distinguish spring- and autumn-flowering types, which have been converted to text labels above.

Recommended varieties:

• Crocus chrysanthus: 'Cream Beauty', 'Ladykiller', 'Snow Bunting'
• Crocus tommasinianus: 'Ruby Giant'
• Crocus vernus: 'Little Dorrit', 'Queen of the Blues', 'Vanguard'