Watering
- Newly planted zantedeschias should be watered regularly until established.
- They like consistent moisture, so keep them well watered through the growing season if your soil is at risk of drying out.
- Plants in containers can dry out quickly, as they have less access to water. So these should be watered regularly during the growing season.
- Water only sparingly in winter, otherwise the roots may rot.
Feeding
Hardy arum lilies should perform well without additional feeding, if grown in fertile soil that is rich in organic matter.
On poorer soils, or to boost growth, you can feed with a balanced liquid fertiliser every fortnight through the flowering period.
Tender calla lilies can be fed during the growing season, especially when in containers:
- Apply a balanced liquid fertiliser fortnightly until the flowers fade
- To boost flowering, you can replace the balanced feed with a potassium-rich feed, such as tomato fertiliser, applying once a week until flowering is over
Mulching
With hardy arum lilies growing in the ground, apply a generous mulch of organic matter, such as well-rotted garden compost, over the root zone in autumn.
This will help to hold in moisture and deter weed germination. It will also insulate the roots, protecting them from freezing over winter.
Deadheading
Remove the flowers once they start to fade, pulling out the entire stem at the base.
This encourages the formation of new flowering stems, to prolong the display.
See our guide to deadheading.
Overwintering
In the ground
Hardy Zantedeschia aethiopica and its cultivars can be left in the ground over winter in most parts of the UK. Still, in all but the mildest areas:
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Lay a thick, insulating layer of mulch on the soil, covering the area in which the roots are growing (typically about 30cm/1ft all round the plant)
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Alternatively, protect the overwintering plants by cutting back and covering with straw or bracken, anchored with pegged-down chicken wire
The older and more established the plant is, the hardier it should be. Young plants should be given extra protection even in mild areas.
Tender calla lilies (mainly cultivars of Z. elliottiana and Z. rehmannii) should be brought indoors over winter, as most will not survive below 5˚C (41˚F). Dig up the plants in autumn, before the first frost, and either:
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Replant into containers and keep them above 10°C (50°F). They need a few months of dormancy, so let the leaves die down and keep them out of bright light, with little or no water
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Cut off the fading leaves and remove the soil from around the bulb-like rhizomes, then dry them off. Store in trays of compost in a cool, dark, frost-free place such as a garage or shed
If you live in a mild area or have a very sheltered garden, you may choose to risk leaving these plants in the ground. If so:
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Insulate the roots with a thick (minimum 15cm/6in) layer of mulch, such as well-rotted garden compost
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Alternatively cover with a cloche or with at least a 15cm (6in) layer of straw/bracken, held in place with chicken wire
In containers
When grown in containers outdoors, the roots are more exposed to the cold, so even hardy types need protection.
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Hardy arum lilies can be left outside if moved to a sheltered spot and/or the container is insulated with several layers of fleece. Hessian and straw are useful plastic-free alternatives
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Tender calla lilies in containers should always be brought indoors. Keep them dry and frost free
See our guide to winter protection.
Indoors as houseplants
Give calla lilies a period of dormancy over winter, with little or no water, and ideally in the dark. Too much water, especially when not in growth, can cause the rhizomes to rot.
Increase the watering in spring once shoots start to appear, but never let them stand in water.
Caring for older plants
Over time, Zantedeschia aethiopica can form large, dense clumps, and flowering may be reduced due to overcrowding. If this happens, lift and divide the clump in early spring. The resulting smaller plants should be full of vigour and flower well once settled in.
See our guide to dividing perennials.