How to Grow Peacock Irises in Australia

Peacock iris (Moraea aristata) is a low-growing member of the iris family Iridaceae that grows from a corm. It is grown for white, iris-like flowers with an iridescent blue eye at the base of each outer petal. Botanists once called it Iris pavonia, and the peacock moraea (Moraea villosa) is a close cousin. It grows through winter and rests over summer, which suits the dry-summer south, and summer water rotting the corms is the commonest failure.

Three mistakes that matter

1. Watering the bed in summer. From late spring to autumn the corms sit dormant, and soil that stays damp through that rest lets fungal rot in. Choose a spot that drains fast, turn the hose off when the leaf yellows, and leave the bed dry until autumn.
2. Letting the soil dry out while the leaf is green. Leaf and flowers are built on winter and spring moisture, and a dry spell then can cost a season of flowers. Water deeply whenever the top few centimetres of soil dry out, from planting until the leaf yellows.
3. Letting it seed or dumping spare corms. Peacock iris has gone wild in south-western Victoria, and its cape tulip cousins are declared weeds that poison livestock. Snip off each flower stem when its last bloom fades, so no seed ripens, and put spare corms in the rubbish bin.

When to plant

Autumn is planting time: wait until the summer heat has broken and nights are turning cooler. In most southern gardens Anzac Day falls inside the window. The leaf grows through winter, and the flowers open from late winter into spring, once a year.

Corms that arrive during a late heatwave can wait for cooler nights, stored as under Harvesting Blooms.

Site, soil and setup

After a loss to rot, start again with sound corms somewhere drier, not in the bed that failed.

Weed status, state by state

Peacock iris is critically endangered in the wild near Cape Town, yet it has naturalised in south-western Victoria. Its relatives the cape tulips, one-leaf (Moraea flaccida) and two-leaf (Moraea miniata), are declared weeds of pasture across southern Australia. No state or territory list names peacock iris itself, but the Tasmanian listing of cape tulips is broad enough to check first.

The same habits apply in every state: deadhead before seed ripens and bin spare corms, as under Three mistakes. Old potting mix from a peacock iris pot can hide cormlets, so bag it too rather than spreading it near bushland or a paddock.

Container growing

Outside the tropics, peacock iris grows well in a pot. Where summer brings storms, a pot is the surest way to grow it, because the resting corms can be carried out of the rain. Choose a deep pot with drainage holes, 30 cm or more across and holding about 15 L. Use premium potting mix lightened with a few handfuls of coarse sand, and plant corms 3 cm deep, 10 cm apart.

The store sells one form, the white flower with a blue eye, which reaches about 20 to 35 cm tall. Corms tend to sink to the bottom of a pot, so tip it out and replant each year once the leaf withers.

• Watering. Soak the mix after planting. While the leaf is green, water again each time the surface feels dry, then let the pot dry out completely once the leaf turns yellow.
• Feeding. Give seaweed solution at 30 mL per 9 L once a fortnight through leaf growth. From first bloom until the leaf fades, switch to liquid potash at its label rate, also fortnightly.
• Position. A sunny spot from autumn to spring, then a dry shelter, such as a carport or under the eaves, for summer.

Planting Corms

What arrives in the pack is a corm (a short, solid storage stem replaced each year), planted while dormant.

Planting a bed

1. Ready the soil with compost and bone meal, as the table under Site, soil and setup sets out.
2. Sort the corms and set aside any that are shrivelled or mouldy.
3. Push each corm in tip upward so about 3 cm of soil covers it, which is around double its width.
4. Space corms about 10 cm apart, so cormlets have room to fill out a clump.
5. Water in well to settle the soil, then keep it lightly moist as the leaf appears.
6. Push in a label or stake, since the patch is bare all summer and easy to dig into by mistake.

Lifting and dividing

Where summers are reliably dry, the corms can stay put for years. Cormlets (small new corms) form at the tips of short underground runners and slowly build a clump. Once flowering thins out from crowding, dig the clump after the leaf has died back and split it. Brisbane-style humid summers, or a bed that gets summer irrigation, call for digging the corms annually as the leaf browns.

Twist the cormlets free of the parent corm and throw away anything soft. Replant them in autumn, or pot cormlets up singly to grow on.

Care by growth stage

Flowering rests on three things: generous water through winter, plenty of sun, and a summer with no water at all. Feed lightly.

If growth stalls in poor soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) scratched into the surface in autumn can help. Established clumps also welcome a 5 cm mulch of compost spread over them before the leaf emerges.

Companion planting

The best neighbours want the same sun, sharp drainage and dry summer, and low ones hide the leaf as it dies down.

Grows well with

• Lavender, a sun lover that copes with dry summers once its roots are established.
• Rosemary, an evergreen backdrop that fills the gap left by the dormant corms.
• Catmint, whose soft grey growth screens the dying leaf in late spring.
• Dianthus, a short edging plant that shares the taste for gritty, fast-draining soil.

Keep apart

• Dahlias and canna lilies, thirsty summer growers whose watering would soak the dormant corms.
• Any watered lawn or drip-irrigated bed, where summer moisture reaches the corms.
• Boundaries next to bushland, a creek line or grazing land, which escaped cormlets and seed can reach.

Harvesting Blooms

For a vase, choose a stem whose top bud is swollen and showing white, still closed.

• Pick soon after sunrise, before the day warms and the stems lose water.
• Snip with clean, sharp secateurs and drop each stem into a jug of water as you go.
• Take the flower stem only, and leave the single leaf on the plant until it has withered completely.

In the garden each flower lasts about three days, but a clump keeps opening new ones for three to four weeks. Lifted or newly bought corms keep best completely dry, in a paper bag in an airy cupboard, until autumn planting.

Common problems

Healthy leaf, no blooms. Shade, crowding, a leaf cut while green or dry soil in growth can leave corms too weak to flower. Divide crowded clumps as under Planting Corms.

Pots that flower less each year. The corms have sunk, so tip the pot out and replant as under Container growing.

Seedlings or new plants beyond the bed. Seed or wandering cormlets are the cause. Lift each stray, corm and all, while its leaf still shows, and send it out in the rubbish.

Pests and diseases

Peacock iris is not especially prone to pests, and most trouble comes from summer moisture or hot, dry spring weather.

Spider mites (Tetranychus species). Spider mites often attack the undersides of peacock iris leaves as temperatures rise in late spring, leaving them stippled and pale. Spray horticultural oil on the undersides at its label rate, in the cool of the day. Read more

Corm rot (fungal). Corms kept damp over summer often rot and turn soft, and the leaf may fail to appear in autumn. Discard soft corms and start again as under Site, soil and setup.

Garden snail (Cornu aspersum). Common in gardens all over Australia, snails may graze the tender leaf in autumn and winter. Hand-pick them on damp evenings. Read more

Prevention first

• Plant only firm corms, and throw out any soft ones found at lifting.
• Check leaf undersides for fine webbing once spring turns hot.
• Spare the small black mite-eating ladybirds by avoiding broad-spectrum sprays.
• Rake away dead leaves and old stems once the clump goes dormant.

Tips

1. Sink an old colander into the bed and plant the corms inside it, so lifting takes one scoop.
2. Plant a few corms beside a path or in a pot by the door, where the small flowers can be seen up close.
3. In wet-summer zones, split the corms between the bed and a pot kept under cover, as insurance against a stormy summer.

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