How to Grow Calla Lilies in Australia

Calla lilies (Zantedeschia hybrids) are tuberous perennials in the arum family (Araceae), grown for their sculpted, funnel-shaped flowers in summer beds, pots and vases. They come from southern Africa and are not true lilies, which belong to the genus Lilium. The coloured hybrids grow from Tasmania to Queensland. The usual stumble is water: too much on a sleeping tuber, then too little once the leaves are up.

Three mistakes that matter

1. Watering a tuber before it sprouts. A dormant tuber in cold, wet soil can rot before a leaf appears, and the coloured hybrids rot far more readily than white arum lilies. Plant into barely damp, free-draining soil and hold off watering until shoots show.
2. Letting the soil dry out in summer. Drought tells a calla its season is over, so the leaves yellow early and flowering stops. Keep the soil evenly moist from the first leaf to the last flower, and mulch beds.
3. Planting in heavy shade. Callas with less than about six hours of direct sun make plenty of leaves but few flowers. Choose a spot in full sun.

When to plant

Plant tubers (swollen underground stems that store food) once frosts are over and the soil is warming. Outside the tropics, that falls between late winter and late spring. Cold soil leaves a tuber idle and open to rot. Flowers follow in late spring or summer in most zones, and the clump can return each year.

In frost-free gardens, tubers can stay in the ground all year and simply resprout. Where frost lingers, get a head start as under Starting in pots.

Site, soil and setup

Coloured callas want sun, shelter from hot summer wind, and soil that stays moist without ever sitting wet. That last point separates them from the white arum lily, which grows happily in boggy ground.

A clump can stay in one spot for years, so rotation does not apply. After soft rot, plant fresh tubers in a different bed.

Calla or arum lily?

Both are Zantedeschia, and both get called calla lilies, which causes plenty of confusion. The white arum lily (Zantedeschia aethiopica) is a larger plant, usually 1 to 1.5 m tall, that thrives in wet ground. It has escaped gardens into creeks, wetlands and pasture. The coloured callas are hybrids, mainly of Z. elliottiana and Z. rehmannii, and stand about 30 to 75 cm tall. The declarations below name the white arum lily.

Arum lily spreads in dumped garden waste, so bin unwanted tubers of any Zantedeschia or ask your council how to dispose of them.

Container growing

Callas suit pots, where they tend to stay more compact than in the ground. Use a pot at least 15 cm wide, about 1.9 L, for one tuber, or 30 cm wide, about 14.5 L, for three. Choose one with drainage holes and fill it with premium potting mix. 'Dreamland', 'Dubai Nights', 'Night Club' and 'Picasso' all make good pot plants.

• Watering. Once shoots appear, keep the mix evenly moist, as pots dry out faster than beds. See watering pots through summer.
• Feeding. Give fish and seaweed blend at 25 mL per 9 L every fortnight from the first leaves until the leaves begin to yellow.
• Position. Morning sun and afternoon shade, out of hot wind. A pot in flower can come indoors for a few days.
• Winter. Once the leaves die down, stop watering and keep the pot dry and frost-free until spring.

Planting Bulbs

Callas are sold and planted as dormant tubers, often called bulbs, set straight into the bed or a pot.

Planting direct

• Choose firm tubers and discard any that are soft or smell foul.
• Find the rough, knobbly side with the growing eyes (buds) and set it facing up. If you cannot tell, lay the tuber on its side.
• Plant 10 cm deep, or up to 15 cm deep in hot districts to keep the tuber cooler.
• Space tubers 20 to 30 cm apart.
• Shoots usually appear in about two weeks in warm soil, and flowers follow 7 to 12 weeks after planting.

Starting in pots

In cold districts, pot tubers under cover in late winter, with about 5 cm of mix over them. After the last frost, harden them off (give them a week or so of longer daily stays outdoors). See hardening off seedlings. Plant each one at the depth it grew in the pot.

Care by growth stage

Callas are light feeders, and too much nitrogen buys leaves instead of flowers. Water matters more than feed: it rises with the leaves and falls away after flowering.

Week ranges run from planting and shift with the weather. If growth stalls in poor soil, a light dose of all-purpose controlled release granular (NPK around 14-5-10) scratched into the soil can help.

Where the ground freezes or winters stay wet, lift tubers in late autumn once the leaves have died back. Crowded clumps also need lifting, as in dividing perennials.

• Dig carefully, because a bruised tuber invites soft rot.
• Brush off the soil and dry the tubers for a few days in an airy spot.
• Store them dry and dark at about 10 to 16°C until spring.
• Divide crowded clumps every three to four years, cutting so each piece keeps a growing eye.
• Let the cut surfaces dry and heal before replanting.

Companion planting

Low, shallow-rooted plants that like the same moist, sunny bed make the best neighbours.

Grows well with

• Alyssum, a low carpet that draws hoverflies, whose larvae eat aphids.
• Lobelia, a shallow-rooted edging that leaves the tubers room.
• Begonias, which like the same moist, rich soil and stay below the flowers.

Keep away anything that shares their virus or crowds their crowns.

Keep apart

• Dahlias and asters, frequent hosts of spotted wilt and the thrips that spread it.
• Dense spreading groundcovers, which smother new shoots and hold damp around the crown.
• Lavender and other dry-country plants, which want the summer dryness that callas cannot take.

Harvesting Blooms

Pick a flower once its spathe (the coloured, funnel-shaped bract) has fully opened, before the central spike sheds pollen.

• Cut the stem low, or pull the whole stalk from its base with a firm tug.
• Pull spent flowers the same way, which keeps new stems coming.
• Leave every leaf in place, because the leaves feed the tuber for next year.
• Stand stems in clean water as soon as they are picked.

Picked at the right stage, callas can last up to two weeks in a vase. Stems can also wait dry in the fridge, at about 5°C, for three to four days before arranging.

Common problems

No flowers. Too much shade, too much nitrogen or a young tuber is usually to blame, and clumps often flower more strongly as they settle. Move them into more sun and use the feeds under Care by growth stage.

Tubers that never come up. Cold, wet soil after planting rots tubers (see Three mistakes that matter). Dig one up: a firm tuber is still waiting for warmth, while a soft one has rotted. Read more

Scorched, brown leaf edges. Hot afternoon sun or dry wind burns the leaves, most often in inland and northern gardens. Give afternoon shade and keep the soil moist.

Spotted leaves in humid weather. Fungal leaf spot can mark the leaves in warm, humid spells, unlike the pale streaks of spotted wilt. Water at soil level and improve airflow around the clump.

Leaves yellowing in late summer or autumn. This is the normal slide into dormancy once flowering ends. Ease off watering and let the leaves die back on their own.

Pests and diseases

Snails, thrips, aphids and soft rot are the usual troubles, and both insects can carry viruses.

Garden snail (Cornu aspersum). Snails and slugs chew young leaves and buds, feeding mostly at night and in cool, wet weather. Pick them off by torchlight after rain. Read more

Western flower thrips (Frankliniella occidentalis). These tiny insects feed deep inside the flower funnel, where sprays struggle to reach, and they spread spotted wilt. Clear weeds nearby, since they shelter thrips. Read more

Aphids, including green peach aphid (Myzus persicae). These small, soft insects cluster on new leaves and flower stems, leave sticky honeydew and can spread mosaic viruses. Hose off small colonies. Read more

Bacterial soft rot (Pectobacterium carotovorum). Tubers turn soft, slimy and foul-smelling, and plants can collapse at soil level. The bacteria enter through wounds and thrive in warm, wet soil. An infected tuber cannot be saved, so lift it and bin it.

Spotted wilt (Orthotospovirus tomatomaculae). Leaves, leaf stalks and flower stems show whitish or yellow streaks and spots, sometimes with small rings. Infected plants cannot be cured, and the virus can travel in tubers, so bin the whole plant.

Prevention first

• Plant only firm, unblemished tubers, and handle them gently.
• Water at soil level, and never leave pots standing in saucers of water.
• Keep weeds down around the bed, as they host thrips and spotted wilt.
• Check new leaves for snails after rain and on mild evenings.

Tips

1. Pair a dark variety such as 'Cantor' or 'Night Club' with the white and pale pink of 'Crystal Blush', so each colour stands out.
2. Grow speckled-leaf types such as 'Picasso' and 'Morning Sun' where they are seen up close, as the leaves stay decorative after the flowers fade.
3. In frost-free gardens, leave clumps undisturbed for a few years, because callas resent root disturbance and often flower best once settled.

Due to quarantine restrictions and our shipping policy, we cannot send calla lily bulbs to Western Australia or Tasmania.