How to grow zantedeschia

Zantedeschia (aka calla lilies) are a popular cut flower and also make great garden plants, providing beautiful blooms from June to September. Growing them in pots works well, as this allows you to put them on the patio or drop them into the border to fill a gap. They come in a fantastic selection of colours and have dramatic furled flowers, but can something so tropical-looking and tender really be easy to grow? 

To find out, Which? Gardening magazine grew 19 varieties at our north London trial ground, including some popular types as well as some more unusual ones from specialist nurseries. 

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Key facts

PLANT TYPE Tender perennial

POSITION Full or partial sun

SOIL Moist but fertile

How to grow zantedeschias: month by month

Best zantedeschia varieties

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How we test zantedeschia

The rhizomes were planted outdoors By the Which? Gardening magazine researchers at the end of May in 9 litre pots, just below the surface in Best Buy compost for containers with a Best Buy controlled-release feed mixed in. We kept the compost in the pots moist.

We kept track of how well the zantedeschia grew and how long they flowered for, recording the number of blooms and how attractive the foliage was. As zantedeschia produce colourful leaves (bracts or spathes) rather than true petals, they can sometimes lack colour, retaining the green of the leaves, so we also looked at how bright the blooms were.

We noted the plants’ eventual sizes and whether they needed support, as well as how uniformly they flowered, to consider how good they were as plants for pots, and if any had trouble with pests or diseases.

We also tried three techniques for overwintering the plants to see which works best.

Caring for your plants

Planting

If using last year’s rhizomes, clean off old compost or soil, and remove any dead roots and stem bases. Pot them singly into 9 litre pots, with the rhizomes just a few centimetres from the surface. Use a Best Buy compost for containers and mix in a Best Buy controlled-release feed.

If you’re planting before the last frost, keep the plants in a heated greenhouse or indoors in a light situation.

Once the nights are frost free, the plants can be placed outside in a light, sunny, sheltered location. Ideally, the temperature should be over 10°C; this can be as late as mid-June in colder areas.

Watering

Water sparingly until growth starts. Once it’s under way, keep the compost moist. Take care not to overwater zantedeschia, or the rhizomes may rot. 

Feeding

Water with tomato food every two weeks to encourage flowering and support growth.

Overwintering

Zantedeschia won’t tolerate cold, so lift rhizomes or bring in pots before the first frost. When we tried different overwintering techniques, we found that  leaving them in their pots and stored them in a frost-free greenhouse. They resprouted in April and produced their first flowers in June. 

Common growing problems

Yellowing leaves

Yellowing and drooping leaves during the summer are a sign of overwatering and the plant should be moved or left to dry out. This might be a particular problem if the summer is damp.

Aphids and thrips

Aphids and thrips can cause damage to the foliage. Squish any colonies before they get out of control.

Read more about aphids and thrips