Bulb · Araceae
Calla Lily
Zantedeschia aethiopica
Given rich, moist ground and full sun, the calla lifts tall, sculptural blooms into view.
Full sun
Every 2–4 days
USDA 8–10
2–3 ft · 0.6–1 m
Overview
Look closely at a calla and the shape is unmistakable: a single smooth spathe curls and rolls inward at the lip, cupping a slim golden spike that stands upright at its center. It is not a true lily but a member of the arum family, native to southern Africa and carried around the world as a cut flower and a summer bedding plant. The classic spathe is pure white, while the wider clan deepens into cream, soft yellow, and rich wine shades.
Beneath the soil sits a thick, fleshy rhizome, fat and rounded, and from it the plant returns season after season in mild regions. Its tolerance of standing water sets it apart from most bulbs, and the rhizome takes water up to about a foot deep without rotting in active growth. The broad leaves rise on long stalks straight from the ground, so the worry over wet feet that troubles other bulbs falls away here.
For all the polish of its bloom, every part of the plant is toxic to people and animals. The tissue is packed with sharp calcium oxalate crystals that bite the mouth on contact, so the calla is a flower to study with the eyes rather than the tongue. Its leaves and milky sap belong out of the reach of pets and small children.
Care
The short version: full sun to part shade, rich soil kept reliably moist, a balanced feed through the growing months, and the fat rhizomes lifted and split every year or two once the clump grows tight.
Light
The calla opens its strongest, whitest spathes in full sun, and the stalks below them stand taller and straighter for it. It still holds up in partial shade, a help where summer light scorches, though the blooms come a touch softer.
Water
This is a plant whose roots want to stay soaked. Keep the soil consistently moist to boggy and water every 2 to 4 days through active growth, never letting the ground dry around the rhizome. It even stands in water up to about a foot deep, so leaning wet does no harm.
Soil
The fleshy roots take hold best in rich, humusy clay or loam dark with organic matter. Where most bulbs would rot, the calla rhizome endures poor drainage and the odd flood, and it sits content across a pH band from 6.0 to 8.0.
Temperature
The plant carries on across roughly 10°F to 86°F (-12°C to 30°C), with its leaves and blooms at their crispest in mild summer warmth. A hard freeze blackens the foliage and drives the plant into dormancy, so the rhizomes want lifting or a thick mulch where winters bite.
Humidity
The broad leaves hold up best in air on the humid side, in keeping with the plant's home in damp ground and at pond margins. Dry air alone will not scorch them as long as the soil around the roots stays moist.
Feeding
A balanced general-purpose fertilizer goes on monthly through spring and summer while the leaves and flower stalks push hard. As the foliage yellows and slackens toward dormancy, the feeding tapers off with it.
Pruning
Snip the spent flower stalks at the base and pull any leaf that yellows or browns to keep the clump clean. When the whole crown dies back for the season, cut it down to the ground as the plant slips into dormancy.
Repotting
The rhizomes get divided and repotted every 1 to 2 years, or sooner once they knot together. Fat rhizomes packed to the pot wall, a thinner crop of spathes, and pale roots threading out the drainage holes all show the clump has run out of room.
Size & spacing
A mature calla lifts its leaves and blooms 2 to 3 feet (61 to 99 cm) off the ground and spreads its clump 12 to 24 inches (30 to 61 cm) across. The rhizomes go in about 12 to 18 inches (30 to 46 cm) apart so each one has space to thicken and fill.
When to plant
The calla stirs from its rhizome only as the soil warms. In cold-winter areas, the rhizomes start indoors in late winter, then go out once frost has cleared. The first curled spathes unfurl in early summer, and the flowers stand at their fullest through June and July.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Start rhizomes indoors in late winter to early spring in cold-winter areas.
- Plant: Plant rhizomes outdoors in spring after frost, 3-4 inches deep and 12-18 inches apart.
- Harvest: Blooms June to July.
Hardiness
USDA hardiness zones: 8–10
Temperature: down to -12°C
Troubleshooting
A calla shows its troubles either at the rhizome below or across the broad leaf blades above. Rot in waterlogged ground is the one that runs deep, while beetles and thrips mark the surface more than they wound. Match the look of the damage below to its cause and step in early.
Soft, mushy rhizome and collapsing leaves
When the rhizome turns soft and slick and the leaves slump and fold to the ground, the trouble is rhizome rot, set off by soil that stays waterlogged and airless. Dig the rhizome up and feel it over: brown, mushy, foul-smelling flesh has to come out. Pare the soft patches from a firm rhizome worth keeping, let the raw cuts dry and skin over, then bed it back into looser, better-drained ground.
Fix:
- Lift affected rhizomes and discard rotted ones
- Cut away soft tissue from salvageable rhizomes and let cure
- Replant healthy rhizomes in better-drained, aerated soil
Leaves chewed to lace and flowers torn up
Leaf blades eaten down to a lacy skeleton and spathes left ragged are the mark of Japanese beetles, hard-shelled insects of metallic green and bronze that cluster over foliage and flowers through summer. Flick them off by hand into a tub of soapy water. Keep at a plant that is heavily chewed, since stripping the early ones off leaves fewer to settle in and feed.
Fix:
- Handpick beetles into soapy water
- Reduce populations on heavily infested plants
Silvery, stippled patches on the leaves
A dull, silvery stippling spreading across the green, often peppered with tiny black frass specks below, points to banded greenhouse thrips scraping at the leaf surface. Tear off and bin the most silvered, speckled blades. Then keep the plant well fed and watered, because a vigorous calla pushes fresh growth that outpaces the light scarring thrips leave.
Fix:
- Remove and dispose of heavily infested foliage
- Improve growing conditions to support plant vigor
Toxicity
No part of the calla is safe to bite. The flesh of every part holds insoluble calcium oxalate crystals, slim needle-shaped raphides that pierce soft tissue on contact and set off instant burning, drooling, and swelling. The crystals act the same in cats, dogs, horses, livestock, rabbits, birds, and people, and the clear sap can leave bare skin raw, so wash hands after handling and keep the leaves and stalks out of reach of pets and children.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Toxic
A cat that sinks its teeth into any part feels the sting at once and paws hard at its mouth, drooling in long strings and vomiting. The lips and tongue puff and swell, and each swallow turns painful as the crystals work the tissue.
Dogs Toxic
A dog that chews a leaf or licks the sap drools heavily and gags, its mouth often swollen and raw. The crystals sting so fast that most pull away at the first bite, so they seldom swallow enough to do any lasting harm.
Horses Toxic
In a horse the crystals scald the lining of the mouth and the tongue, raising swelling, heavy drooling, and a plain refusal to eat. A horse cannot vomit, so the hurt shows as a sore, tender mouth and feed left in the trough.
Rabbits Toxic
The same insoluble calcium oxalate that bites cats and dogs scrapes a rabbit's mouth and gut just as raw. Keep the callas, any cuttings, and every dropped leaf well clear of a rabbit grazing nearby.
Livestock Toxic
Cattle, sheep, and goats that crop the leaves get a raw, irritated mouth and throat, drooling, and a churning gut. The harsh, acrid taste usually turns them back, but a hungry animal on thin pasture may chew it anyway.
Birds Toxic
The leaves and clear sap hold the same biting crystals for birds, so a parrot or chicken that pecks at them can end up with a sore, swollen mouth. The plant is best kept well clear of birds altogether.
People Caution
No part of a calla can be eaten, and a single bite sets the lips, tongue, and throat burning at once, with drooling and swelling close behind. The sap on its own leaves skin itchy and raw, so wash up after handling and keep children well clear of the leaves and stalks.
Keep plant, cut flowers, and sap away from pets and children; wash hands after handling as the sap can cause skin and mouth irritation.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Most callas in the garden are selections of the white arum lily, picked for the size or coloring of the spathe. These two show up most often.
White Giant
White Giant carries oversized, pure white spathes, the largest and most eye-catching blooms among the classic callas.
Green Goddess
Green Goddess opens white deep in the throat and washes into clear green toward the curled tips, so each spathe wears two tones at once.
How to propagate
Callas are easy to increase, and splitting the fat rhizomes of a settled clump is the quickest way to raise more flowering plants.
DivisionEasy
Early spring or late summer to early fall · One growing season
The easiest way to raise more callas is to break apart a crowded clump of rhizomes. Lift them in early spring or in the cooler stretch from late summer into fall and pull the fat sections apart by hand. Each firm, healthy piece roots down and fills out into a full clump over a single growing season.
SeedModerate
When ripe seed is available · Multiple seasons to flowering
Growing from seed is the slow road. Sow the ripe seed when it is available, but the small seedlings spend several seasons bulking up their rhizomes before a single spathe appears. Splitting rhizomes is far faster for more flowering plants.
Bulbs & cormsEasy
Spring · One growing season
Most growers start from bought rhizomes, plump and dormant. Set them in the ground in spring, 3 to 4 inches deep and 12 to 18 inches apart, and they send up leaves and flower within their first season.
Myths
The calla lily is a true lily and causes fatal kidney failure in cats like Easter and tiger lilies do.
The bloom may suggest a lily, but the calla is no true lily at all; it sits in the arum family. It does not bring on the deadly kidney failure that true lilies cause in cats. Its tissue instead carries insoluble calcium oxalate crystals, the slim needles that burn the mouth and set off drooling and vomiting in cats and dogs, painful but rarely life-threatening.