How to Grow Crocus in Australia

Crocus (Crocus vernus and its Dutch hybrids, and the yellow Crocus x luteus) are small corms in the iris family Iridaceae. They are grown for cup-shaped flowers in white, purple, striped and yellow from late winter into early spring. Planted in autumn, they brighten lawns, rockeries and pots wherever winters turn properly cold. The one thing most gardeners get wrong is expecting them to flower after a mild, frost-free winter.

Three mistakes that matter

1. Expecting flowers after a warm winter. Dutch crocus need a long spell of cold to flower, and a mild winter often gives leaves and nothing more. In warm districts, chill the corms in the fridge first, as under Chilling, and treat them as annuals.
2. Mowing or cutting the leaves too soon. The grassy leaves feed the corm for next year, so cutting them while green weakens the clump. Leave them for about six weeks after flowering, until they yellow, before mowing a crocus lawn.
3. Wet soil while the corms rest. Corms rot in soggy ground, above all when summer sprinklers run over a dormant bed. Plant in free-draining soil, a raised bed or a pot, and water only while the leaves are green.

When to plant

Plant corms in autumn, from March to May, once the soil has cooled after summer; Anzac Day sits in the middle of that window. What decides flowering comes later: a long run of cold winter weeks, which the cool and alpine zone and the cooler temperate districts give reliably.

In warm districts, chill corms first and plant at the cool end of the window, in May.

Site, soil and setup

Crocus want winter sun on their leaves and soil that drains fast, because they grow through the wet months and rest dry in summer.

Plant new corms in fresh soil rather than where bulbs have rotted, because rots and bulb mites can persist there.

Weed status, state by state

No state or territory declares spring crocus a weed, and in gardens they tend to naturalise without turning weedy. Councils can keep their own lists, so check yours before planting next to bushland.

Container growing

Pots suit crocus in every zone where they grow, and a pot can sit in the coldest corner of the garden over winter. Use a pot at least 15 cm across and 20 cm deep (about 3 L), with drainage holes. A pot that size holds up to 15 corms. Fill it with free-draining potting mix and crowd the corms in, close but not touching. All four store varieties stay low, at about 10 cm.

• Watering. Keep the mix just moist while the leaves are green, checking with a finger a few centimetres down. Never leave the pot standing in water.
• Feeding. From the first leaves, water in seaweed solution at 30 mL per 9 L every fortnight. Once flowering ends, switch to liquid potash at the label rate every fortnight until the leaves yellow.
• Position. Full sun in winter, then somewhere dry once the leaves die down.

Planting Bulbs

Crocus start from dormant corms, small and flattened in a papery skin, planted pointed end up.

What the store sells

The Royal Horticultural Society treats 'Yellow Mammoth' as a name for Crocus x luteus 'Golden Yellow', the old yellow Dutch crocus. All four are planted and grown the same way.

Chilling

Corms for the subtropics, the warm coast and any frost-free garden need a false winter before planting. Put them in a paper bag in the fridge crisper at 2 to 7°C for six to eight weeks, then plant straight away. This gives them their best chance of flowering, not a certainty. Keep fruit out of that fridge, because ripening fruit gives off ethylene gas, which harms flower development. Corms for the cool and alpine zone need no chilling.

Planting a bed of corms

1. Prepare the bed as under Site, soil and setup.
2. Set each corm pointed end up, 10 cm deep, or 12 cm deep in a lawn.
3. Space corms 7 to 10 cm apart, in clumps or drifts rather than single rows.
4. For a natural look, toss a handful across the ground and plant each where it lands.
5. Water in well, then water again only if the soil dries out.
6. Mark the spot, so a spade does not find the corms before the shoots appear.

Spring crocus, saffron crocus and autumn crocus

The store's crocus are spring crocus, grown only for their flowers. Saffron crocus (Crocus sativus) flowers in autumn and gives the spice; it has its own saffron guide. Autumn crocus belongs to its own family, the Colchicaceae, and flowers in autumn before its leaves appear.

After flowering: keep, lift or divide

The leaves usually yellow by late spring or early summer, and the corms then rest until autumn. Crowded clumps flower less, so lift and divide them every three to five years in late summer, while they are dormant. Replant the offsets straight away, or store them as under Harvesting Blooms.

Care by growth stage

Cold weeks in winter, moisture while the leaves are green and a dry summer rest decide how well crocus flower. Feed lightly at planting, then give potassium as the leaves finish their work.

Crocus in good garden soil often need little more than this. If growth stalls in poor soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) scratched in as the shoots appear can help.

Companion planting

Crocus pair best with plants that share their cool, wet-winter and dry-summer rhythm.

Grows well with

• Daffodils, which flower alongside crocus and want the same dry summer rest.
• Scilla and hyacinths, other autumn-planted bulbs for the same sunny, free-draining bed.
• Deciduous trees, which stand bare and let in full sun while crocus flower.
• Short, sparse lawn grass, which the Dutch types colonise if mowing waits for their leaves.

Keep apart

• Vegetable beds and saffron plantings, where corms that are not to be eaten could be dug up by mistake.
• Thick, vigorous lawn or groundcover, which crowds the small corms and shades their leaves.

Harvesting Blooms

Crocus flowers open wide in the morning sun and close at night and on cloudy days. Enjoy them where they grow, on sunny days.

• Deadheading is not needed, though spent flowers can be pinched off for tidiness.
• Lift corms from pots once the leaves die down.
• For indoor colour, plant corms in moist potting mix and chill the pot in the fridge for 15 to 17 weeks. Keep the mix moist but not wet, and bring the pot to a cool, bright spot once shoots show.
• Keep forced corms potted until the leaves die down, then plant them out in autumn, because they will not force again.

Store lifted corms in paper bags somewhere cool and dry until autumn, and check them as under Prevention first before replanting.

Common problems

Leaves but no flowers. A warm winter, leaves cut early the spring before, or an overcrowded clump can stop flowering (see Three mistakes). Chill corms in warm districts and divide crowded clumps.

Flowers that stay shut. Crocus open only in sunshine, so a shaded spot keeps them closed. Move clumps into winter sun, such as under deciduous trees.

Weak or late shoots. Corms planted far too deep can exhaust themselves before they reach the surface. Plant at the depths under Planting Bulbs.

Corms gone after planting. Small holes in the soil in the first autumn or winter usually point to mice; see Mice and rats under Pests and diseases. For rotting corms, see Three mistakes.

Pests and diseases

Crocus pests mostly attack the corm, in the soil or in storage.

Mice and rats (Muridae). Rodents dig down to gnaw newly planted corms, most often in the first autumn and winter after planting. Lay wire mesh over new plantings, and keep spare corms in a closed container. Read more

Tulip bulb aphid (Dysaphis tulipae). Recorded in New South Wales, Victoria, Tasmania and Western Australia, it attacks crocus corms in storage and later feeds at the base of growing plants. Spray insecticidal soap on the shoots, at the rate on its label. Read more

Bulb mite (Rhizoglyphus robini). Recorded in Australia, bulb mites infest crocus corms and travel on infested stock. Badly infested corms rot, and their shoots come up stunted and distorted, so bin them and buy firm, clean corms.

Prevention first

• Plant only firm, healthy corms, and bin any that are soft, mouldy or damaged.
• Handle corms gently, because bruised corms let in rots and mites.
• Store lifted corms cool and dry, which also slows bulb mites.
• Check stored corms before planting for aphids and soft patches.

Tips

1. Plant crocus as the top layer in a pot, above daffodils or tulips, for a longer show.
2. Plant a clump beside a path or window you pass in winter, where the first flowers are easy to see.
3. Where corms must be lifted each year, plant them in an old colander or open basket sunk into the bed, so they lift out together.

Due to quarantine restrictions and our shipping policy, we cannot send crocus corms to Western Australia or Tasmania.