How to Grow Sparaxis in Australia

Sparaxis (Sparaxis tricolor), the harlequin flower, grows from a corm (a swollen underground stem that stores food) and belongs to the iris family, Iridaceae. From the Cape of South Africa, it carries wiry spikes of spring flowers in red, orange, pink, purple, white and yellow. Each has a yellow throat edged in black. It suits Australian gardens with wet winters and dry summers, where a clump comes back for years. The usual mistake is watering it through its summer rest. The bigger risk is letting it spread into bushland, where it is a recognised weed.

Three mistakes that matter

1. Watering through summer. Sparaxis rests as a dry corm from early summer to autumn, and wet soil in that rest rots it. Leave the bed unwatered once the leaves yellow, or lift the corms where summers are wet.
2. Cutting the leaves while they are green. After flowering, the leaves feed the corm that makes next spring's flowers. Leave them until they yellow and wither, which can take six to eight weeks, then pull them away.
3. Leaving clumps to crowd for years. Each corm forms cormlets (small new corms) beside it, and a packed clump flowers less each spring. Lift and divide once flowering declines, after the leaves wither.

When to plant

Plant corms in autumn, from March to May, once the summer heat has broken and the first autumn rain is due. In most southern gardens that means planting by about Anzac Day. Corms sprout in autumn, grow leaves through winter and flower in spring.

Planting can run into early June, though late corms often flower later. Keep waiting corms in their bag in a cool, dark place until the window opens, rather than planting into baking summer soil.

Site, soil and setup

Sun and drainage decide how well sparaxis flowers. It grows on sandy or loamy soil, and copes with clay only where water never lies around the corms.

A clump stays put for years, so rotation does not apply; replant divided corms into freshly composted soil.

Weed status by state

Sparaxis has run wild across southern Australia from old gardens. The white-flowered Sparaxis bulbifera spreads by seed and by bulbils (tiny corms in the leaf joints). Sparaxis tricolor and its hybrids spread by seed, cormlets and a few bulbils in the lowest leaf joints. In Australia the name Sparaxis grandiflora has often been misapplied to Sparaxis bulbifera. No state or territory declares any sparaxis a pest plant. Victoria lists two as environmental weeds, and both are recorded as bushland weeds in South Australia and Western Australia.

Seed, bulbils and corms travel in water, on mowers and in dumped garden waste. Keep plantings well away from bushland, creeks, drains and wetlands. Seal spent corms, seed heads and pulled clumps in a black plastic bag for the general waste bin. See weed control for clearing a spread clump.

Container growing

Pots suit sparaxis well, because a pot can be moved out of summer rain. A pot at least 30 cm wide, about 14 L, holds a pack of ten corms set 7 to 8 cm apart. Use premium potting mix with a few handfuls of perlite for drainage, in a pot with good drainage holes. Harlequin Mixed grows 25 to 40 cm tall, a good height for a pot.

• Watering. After the first watering, keep the mix just moist from the first shoots through spring, never soggy.
• Feeding. Give seaweed solution at 30 mL per 9 L every fortnight from the first shoots until flowering ends.
• Position. Full sun in winter and spring. Once the leaves yellow, move the pot to a dry, shaded spot, such as a veranda, and stop watering until autumn.
• Repotting. Potting mix breaks down over time, so tip out the corms while dormant and replant into fresh mix every year or two.

Planting Corms

Start with dormant corms planted straight where they are to flower, and they bloom the first spring.

• Plant each corm about 5 cm deep, pointed end up, flat base down.
• Space corms about 10 cm apart, in groups rather than single rows.
• On heavy soil, sit each corm on a pinch of coarse sand to keep the base dry.
• Water once to settle the soil, then wait for shoots before watering again, unless the soil dries right out.

Care by growth stage

A moist winter and a dry summer suit sparaxis, so the watering pattern matters more than feeding. Compost and bone meal at planting carry most of the season.

In poor sandy soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) can help, scratched in as shoots appear. Clumps left in the ground for several years benefit from a fresh 5 cm compost mulch each autumn, kept off the emerging shoots.

Companion planting

Good partners share its liking for sun, sharp drainage and a dry summer, or hide its leaves as they die back.

Grows well with

• Violas and pansies, low spring annuals that can be planted over the corms for colour around the stems.
• Ornamental grasses, which hide the yellowing sparaxis leaves in early summer.
• Low, open groundcovers, which shade the soil around the corms without smothering the leaves.

Keep apart

• Lawns and beds on summer irrigation, because dormant corms rot in wet summer soil.
• Bushland edges, creek banks, drains and wetlands, where seed and cormlets wash or spread into native vegetation.

Harvesting Blooms

Cut stems for the vase once the lowest flower on the spike has opened, so the buds above keep opening indoors.

• Pick in the cool of the early morning, when stems are full of water.
• Carry a bucket half filled with cool water and stand stems in it straight away.
• Cut each stem low, with sharp snips, but leave every leaf on the plant.
• Strip any leaves that would sit below the vase water line.
• Snap off spent stems on plants you are not picking, before seed capsules ripen.

To lift corms, dig them once the leaves have yellowed and withered, shake off the soil and pull the cormlets away. Store them dry in a paper bag or old stocking, hung in a cool, airy shed away from mice. Replant in autumn. Cut stems last well, and look good in a vase with freesias and other spring flowers.

Common problems

No shoots in winter. The corms have most likely rotted in wet soil, or were planted upside down or too deep. Plant at 5 cm, pointed end up, in free-draining soil. Read more

Leaves but few flowers. Shade is one cause, along with crowding and green leaves cut too early (see Three mistakes that matter). Move clumps into full sun when you next divide them.

Clumps gone after a wet summer. Corms left in warm, wet summer soil often rot, most of all in the subtropics (see Three mistakes that matter). Pots that can be kept dry are the safer choice there.

Brown leaf tips after a cold snap. A late frost can scorch new leaves, so mulch beds well in autumn in frosty districts. Read more

Seedlings in paths and lawns. Sparaxis self-seeds and spreads cormlets, and mowing after flowering scatters them further. Dig out strays with the whole corm, and deadhead as under Harvesting Blooms.

Pests and diseases

Sparaxis has few pests, and most losses come from wet soil.

Garden snail (Cornu aspersum) and slugs. They chew new shoots and flower buds at night, worst on wet evenings after rain. Hunt them by torchlight, or set beer traps sunk to the rim. Read more

Aphids (family Aphididae). Clusters of small sap-suckers gather on buds and new growth, leaving sticky honeydew that draws ants. Hose them off, and spray soapy water or horticultural oil only in cool weather. Read more

Corm rot (soil fungi). Corms turn soft or shrivel and send up stunted yellow leaves, or none at all. Wet soil during dormancy is the usual trigger, so bin soft corms rather than replanting them.

Prevention first

• Plant only firm, healthy corms, and discard any that feel soft.
• Clear dead leaves and loose litter where snails shelter by day.
• Check new shoots for snail damage after rain, from planting until the buds open.
• Water at soil level in the morning, so leaves and soil surface dry before night.

Tips

1. Mark clumps with a label or a ring of pebbles, so summer digging does not slice through dormant corms.
2. Grow a few corms in a pot each year for cutting, and leave the garden clump unpicked.
3. Replant only the largest corms in display spots and grow small cormlets on in a spare bed for a season or two.
4. Near a reserve or creek, grow sparaxis only in pots.

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