Arum lily
White callaZantedeschia
White calla
Plant the rhizome about 10-15cm deep in spring in soil that stays moist; it is the hardiest calla, but still worth a winter mulch in its first years.
Care
Sun to part shade; in hot, dry gardens it prefers afternoon shade.
High — a bog plant by nature: it can grow in up to 30cm of water at a pond edge and never wants to dry out in summer.
Moist to wet, humus-rich soil; tolerates heavy clay.
Cut spent flower stems at the base and remove dead leaves in spring. It can be evergreen in mild winters.
A balanced feed in spring and a high-potash liquid feed every two weeks while flowering, especially in pots.
Divide established clumps as growth restarts in spring, keeping a good piece of rhizome with each division.
Month by month
Months change with the climate: in southern Italy tomatoes go out two months earlier than in England.
- AprilFeed and tidy away dead leaves as growth restarts. how ›
- JuneKeep well watered through flowering — it should never dry out. how ›
- NovemberMulch the crown deeply in colder gardens, or move pots somewhere frost-free. how ›
Months based on climate: UK. Your choice stays on this device.
- AprilFeed and tidy away dead leaves as growth restarts. how ›
- JuneKeep well watered through flowering — it should never dry out. how ›
Months based on climate: Northern Italy. Your choice stays on this device.
Common problems
How to spot it. Leaves blackened and collapsed after a hard frost.
What to do. Usually regrows from the rhizome if the crown was mulched; plant deeper in cold areas.
How to spot it. Holes in leaves and grazed flower spathes.
What to do. Protect young growth in spring.
How to spot it. Plenty of leaves but hardly any spathes.
What to do. Usually too dry or too shaded in summer; water more and feed with potash.
Coloured callaGolden calla, Mini calla
Coloured calla
Treat them like dahlias rather than like the white arum: warm and moist in summer, dry and frost-free in winter.
Care
Full sun to light shade — needs warmth and light to colour and flower.
Medium — unlike the white arum, these like moist but well-drained compost and rot if kept wet, especially before growth starts.
Well-drained, fertile compost; add grit in pots.
Remove spent flower stems. When leaves yellow in autumn, let them die back fully before storing.
A high-potash liquid feed every two weeks from the first leaves until the flowers fade, then stop so the tuber ripens.
Separate offset tubers when repotting in spring; large tubers can be cut into pieces each with a growing point, dusted and dried before planting.
Month by month
Months change with the climate: in southern Italy tomatoes go out two months earlier than in England.
- MarchPot up tubers under cover, just covered, and water sparingly until shoots appear. how ›
- JuneMove outdoors to a sunny spot once frost risk has passed. how ›
- SeptemberReduce watering as leaves yellow to let the tubers ripen. how ›
- OctoberLift or bring pots in and store tubers dry and frost-free over winter. how ›
Months based on climate: UK. Your choice stays on this device.
- MarchPot up tubers under cover, just covered, and water sparingly until shoots appear. how ›
- MayMove outdoors to a sunny spot once frost risk has passed. how ›
- SeptemberReduce watering as leaves yellow to let the tubers ripen. how ›
- OctoberLift or bring pots in and store tubers dry and frost-free over winter. how ›
Months based on climate: Northern Italy. Your choice stays on this device.
- FebruaryPot up tubers under cover, just covered, and water sparingly until shoots appear. how ›
- MayMove outdoors to a sunny spot once frost risk has passed. how ›
- SeptemberReduce watering as leaves yellow to let the tubers ripen. how ›
- NovemberLift or bring pots in and store tubers dry and frost-free over winter. how ›
Months based on climate: Central Italy. Your choice stays on this device.
- FebruaryPot up tubers under cover, just covered, and water sparingly until shoots appear. how ›
- AprilMove outdoors to a sunny spot once frost risk has passed. how ›
- OctoberReduce watering as leaves yellow to let the tubers ripen. how ›
- NovemberLift or bring pots in and store tubers dry and frost-free over winter. how ›
Months based on climate: Southern Italy and islands. Your choice stays on this device.
Common problems
How to spot it. Tuber soft and smelly, shoots fail to appear.
What to do. Compost too wet before growth started; keep barely moist until leaves unfurl.
How to spot it. Leaves but no flowers.
What to do. Tuber too small or not enough sun and warmth; feed with potash and grow somewhere brighter.
How to spot it. Clustering in unfurling leaves and flower spathes.
What to do. Wash off or squash.
Questions
Arum lily: is it hardy?
White calla: H4: Hardy through an average UK winter. It survives down to −10 °C. Coloured calla: H1c: Tender, needs above 5°C. It survives above 5 °C.
Can it grow in a pot?
White calla: Yes in a large pot kept wet, or sunk into a pond margin in an aquatic basket. Coloured calla: Yes — the usual way to grow them, so the tubers can be stored dry in winter.
Arum lily: when do you prune it?
White calla: Cut spent flower stems at the base and remove dead leaves in spring. Coloured calla: Remove spent flower stems.
Arum lily: when does it flower?
White calla: In the climate of UK it flowers in May–July. Coloured calla: In the climate of UK it flowers in June–August.
When do you feed it?
White calla: A balanced feed in spring and a high-potash liquid feed every two weeks while flowering, especially in pots. Feeding months, UK: April–July. Coloured calla: A high-potash liquid feed every two weeks from the first leaves until the flowers fade, then stop so the tuber ripens. Feeding months, UK: May–August.