How to Grow Ixias in Australia

Ixia (Ixia hybrids), the corn lily of the iris family Iridaceae, grows wiry stems of starry spring flowers for beds, pots and the vase. The corms come from the winter-rainfall Cape of South Africa, and southern Australia suits them well enough that several species run wild in bushland. The usual failure is a bed kept wet over summer, which rots the resting corms.

Three mistakes that matter

1. Keeping the soil wet in summer. Ixias grow through winter and rest through summer, and corms left sitting in damp soil rot. Plant in free-draining soil, stop watering as the leaves yellow, and keep sprinklers off the bed until autumn.
2. Cutting the leaves off after flowering. The green leaves feed the corm for next spring's flowers. Leave them until they have yellowed and withered, then pull them away. Corms stripped of green leaves often flower poorly the following year.
3. Letting spent stems seed, or dumping old corms. Ixias spread by seed and by small daughter corms, and garden waste carries them into bushland. Cut each stem as it fades, before seed forms, and bag and bin unwanted corms.

When to plant

Plant corms in autumn, once the summer heat has passed and the soil starts to cool. Anzac Day falls in the middle of the window in most southern gardens. One planting flowers once a year, in spring.

Early in the window, wait for the first cool nights rather than planting into hot soil. Corms bought early keep well in a paper bag somewhere dry and airy until then.

Site, soil and setup

Choose the sunniest, best-drained spot in the garden, because most ixia flowers open only in sunshine and the corms rot in wet ground.

Where corms have rotted, replant healthy ones in a different, better-drained spot.

Weed status, state by state

Ixias have escaped from gardens into bushland across southern Australia, where they crowd out the native plants that wildlife feeds on. Only one species, Ixia odorata, is declared, and only in Western Australia. Several others are environmental weeds of bushland in Western Australia and Victoria, and variable ixia has invaded South Australian conservation parks.

In every state, deal with spent stems and spare corms as under Three mistakes. Never tip corms, daughter corms or old bulb soil over a fence or into bushland. Keep seed heads out of green waste, where they can spread through the mulch.

Container growing

Pots suit ixias in every zone and are safest where summers are wet, because a pot can go under cover once the leaves die down. Use a pot at least 30 cm wide with drainage holes, about 15 L or more. Fill it with premium potting mix with a few handfuls of coarse sand mixed through, and plant about 15 corms 5 cm deep.

Candy Mixed carries white, orange, red, purple and yellow flowers with dark centres on 50 to 70 cm stems, so choose a heavy pot. The store also sells 'Elvira'.

• Watering. Water once at planting, then whenever the surface of the mix is dry while the leaves are green. Stop as the leaves yellow and keep the pot dry until autumn.
• Feeding. Water in seaweed solution at 30 mL per 9 L every fortnight while the leaves grow. From the first flowers, switch to liquid potash at the label rate every fortnight until the leaves yellow.
• Position. Full sun while in growth. Move the pot under cover for summer so rain cannot wet the resting corms.

Planting Corms

Ixias start from corms (bulb-like storage stems), planted dormant in autumn with the pointed end up.

Planting a bed of corms

1. Prepare the bed as under Site, soil and setup.
2. Choose firm, plump corms and discard any that are soft or mouldy.
3. Set each corm pointed end up, 5 cm deep, about twice as deep as the corm is wide. If the tip is unclear, lay the corm on its side.
4. Space corms 5 to 10 cm apart, or plant three to five to a hole for a fuller clump.
5. Water in well, then water again only if the soil dries out before the leaves appear.
6. Mark the spot, so a spade does not find the corms over summer.

Lifting and dividing

In dry-summer gardens, leave the corms in the ground, where they multiply into clumps. Lift and divide a clump once it is crowded, usually after four or five years, once the leaves have withered. In the subtropics, and anywhere the bed gets summer water, lift the corms every year as the leaves die.

Separate the small daughter corms from each parent and discard any soft ones. Store them completely dry, somewhere airy at around 20 to 25°C, and replant in autumn.

Care by growth stage

Steady moisture while the leaves are green, full sun and a dry summer rest decide how well ixias flower. Feed lightly and avoid high-nitrogen feeds.

If growth stalls in poor soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) scratched in as the leaves appear can help. Each autumn, before growth resumes, spread compost in a 5 cm layer over established clumps.

Companion planting

Neighbours that share the ixia's taste for sun, sharp drainage and a dry summer suit it best. Low ones also hide its leaves as they die down.

Grows well with

• Lavender, which wants the same sunny bed and dry summer.
• Rosemary, a drought-hardy shrub that fills the space once the ixias die down.
• Catmint, a low grey mound that hides the yellowing ixia leaves.
• Dianthus, low edging that likes the same free-draining soil.

Keep apart

• Dahlias and canna lilies, which need the summer water that rots resting ixia corms.
• Lawns on sprinklers and beds on summer irrigation, for the same reason.
• Garden edges that meet bushland or a creek, where seed and daughter corms escape.

Harvesting Blooms

Cut stems when the lowest buds show colour but have not yet opened.

• Cut in the cool of early morning, when the stems are full of water.
• Use clean, sharp secateurs and stand the stems in water straight away.
• Take the flower stem but leave the leaves on the plant to feed the corm.
• Grow a few clumps just for cutting, so picking does not thin the display.

The buds open in turn up the spike, and a vase can last up to two weeks. Ixias add height and movement to mixed spring posies.

Common problems

Leaves but few or no flowers. Shade, a crowded clump or leaves cut before they yellowed can leave corms too weak to flower; divide crowded clumps as under Planting Corms.

Flowers shut or stems flopping. Shade, dull weather or wind is the usual cause. Move the corms to a sunny, sheltered spot while they are dormant, as under Site, soil and setup.

Ixias coming up outside the bed. Seed or daughter corms have spread; dig the plants out with their corms while the leaves are green, then bag and bin them.

Soft, rotten corms. Wet summer soil is the usual cause, as under Three mistakes; discard soft corms at lifting.

Pests and diseases

Ixias are generally trouble-free, and most problems start with damp corms or soft spring growth.

Aphids (Aphididae). Widespread in Australia, aphids can cluster on ixia buds and young leaves in spring, though seldom badly. Hose them off, or spray an insecticidal soap at its label rate. Read more

Mealybugs (Pseudococcidae). These small, white, waxy sap-suckers can infest corms, especially in pots and in storage. Check corms at lifting and planting, and discard any carrying white, cottony colonies. Read more

Garden snail (Cornu aspersum). Widespread in Australian gardens, snails chew young shoots as they emerge. Hand-pick on damp evenings, or scatter an iron-based bait thinly by its label, where pets cannot reach it. Read more

Prevention first

• Spare ladybirds, lacewings and hoverfly larvae, which eat aphids, by avoiding broad-spectrum sprays.
• Treat ants on pots as a warning sign, since they tend mealybugs and shield them from predators.
• Check new shoots and buds on damp evenings for snails and aphids.
• Clear dead leaves and spent stems from the bed.

Tips

1. Plant clumps in front of summer perennials, which grow up to fill the gap once the ixias die down.
2. Keep a pot of spare corms in wet-summer zones, so one rainy summer does not take the whole planting.
3. Plant corms inside an old colander or wire basket sunk into the bed, so the clump is easy to find and lift.

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