Crocus

Light and exposure

Crocus wants sun, or at least good light. Its cup shaped flowers open wide the moment the sun touches them and close again in the evening, on a cloudy day, or even when a passing cloud blocks the light. Plant it in full sun if you want flowers wide open rather than shyly half closed.

It also does well under deciduous trees and shrubs, a rose, an apple tree, a maple, since it flowers and finishes its cycle before the canopy closes overhead and casts shade. It is one of the few bulbs that makes full use of the light under trees that would be far too shady for almost anything else once summer arrives.

Watering

Once the corms are in the ground in autumn, watering only helps if the soil is genuinely dry at planting time, to get rooting started before the first cold snap. After that, Belgian rain through winter and spring is more than enough, crocus never needs watering while it flowers.

The real risk is not too little water but too much. Once the leaves have died back, the corm goes into summer dormancy and hates sitting in soggy soil. If you grow crocus in pots or containers, let the compost dry out fully through the summer, watering it needlessly at that stage rots the corms faster than any pest would.

Soil and repotting

Crocus is not fussy, ordinary garden soil suits it fine, even poor or stony ground, as long as it drains well. It is equally happy in chalky or neutral soil.

What it cannot stand is standing water. In heavy clay soil, which turns up in patches around the Pays de Herve, loosen the ground well and work coarse sand or fine gravel into the bottom of the planting hole so the corms are not sitting in damp soil through their summer rest.

Temperature and humidity

Crocus is fully hardy in our climate. It shrugs off frost well below minus ten degrees and needs no winter protection at all, no fleece, no thick mulch. In fact it is the cold of winter that triggers flowering once dormancy ends.

This need for cold is exactly why crocus is always planted in autumn and never in spring, it needs several months of cold soil to prepare for flowering. A mild winter with no real cold spell often gives a more scattered, less impressive flowering than a proper cold one.

Pruning and upkeep

There is no real pruning to speak of. The one essential step, and the most often ignored, is letting the foliage die back completely on its own after flowering, over six to eight weeks. It is during this time that the leaves rebuild the corm’s reserves for next year’s flowers.

Never tie the leaves up and never cut them back early, even if they start to look a bit untidy among the other spring plantings. You can deadhead the spent flowers if you prefer a tidier look, but it is not necessary, crocus barely self seeds in a maintained garden.

Pests and diseases

Crocus is one of the healthiest bulbs in the garden, with almost no serious disease here. The one fungal issue worth watching is corm rot in soil that stays too wet over summer, easily avoided with decent drainage.

The real enemy of crocus in Belgium is rodents. Field mice, voles and sometimes squirrels are very fond of freshly planted corms and can empty an entire bed in a few autumn nights. A layer of fine mesh laid in the bottom of the planting hole, or planting in a wire basket, solves the problem. Sparrows and other small birds also sometimes peck at the yellow petals in spring, an unsightly but harmless nuisance.

Propagation

Crocus multiplies entirely on its own, with no help needed. Each corm produces small offset corms around it every year, and the clump naturally grows year after year into dense, generous colonies.

If a clump gets too crowded and flowers less well, dig it up and divide the corms in late spring, once the foliage has fully died back, then replant straight away or store them dry until autumn. Growing from seed is also possible but takes three to four years before the first flower, a method for patient gardeners or amateur botanists.

Month-by-month care calendar

Green Hub tips

• Scatter crocus corms loosely across the lawn rather than planting them in straight rows for a natural look, and always wait until the foliage has turned fully yellow before the first spring mow.
• Protect freshly planted corms with a layer of fine buried mesh if field mice or voles are a problem in your garden, they can strip an entire planting overnight.
• Never confuse autumn crocus or saffron with meadow saffron. The latter looks similar from a distance but is a highly toxic plant that does not belong to the same genus at all.
• Always plant in dense groups of at least twenty corms rather than scattering single corms, the visual effect at the end of winter is not even comparable.