Your Climate Dictates Whether to Winterize Calla Lilies Outdoors or Indoors – Here's How to Overwinter Plants Successfully Both Ways

The calla lily (Zantedeschia aethiopica) is a summer-flowering perennial with trumpet-like flowers and lush, bright green leaves. The tropical plants are popular for bringing abundant color indoors and outdoors, but, as most varieties are tender, you should winterize calla lilies to guarantee blooms year after year.

The exotic summer bulbs are frost-tender, which impacts how they want to be treated for winter. They must be lifted and stored over winter in colder climates, while growers in warmer regions can successfully overwinter calla lilies outdoors.

This guide looks at both methods in detail, plus what to do if you grow the flowers in containers. It includes all the steps you need to know to winterize calla lilies in your climate, helping you to enjoy their stunning flowers for years.

How to Winterize Calla Lilies – Two Different Methods

Your US hardiness zone impacts how you should winterize calla lilies. Whether you live in warmer or cooler climates, these are the steps to follow to overwinter plants successfully.

How to Overwinter Calla Lilies Outdoors in Warmer Climates

If you live in US hardiness zones 8 or higher, it is a simple process to winterize calla lilies outdoors in the ground. The tender rhizome can survive outdoors in climates where there are no deep freezes or long periods of snow. Providing it is a frost-free minimum of 37-40°F, they can overwinter successfully where they are.

One caveat to the above rule is your soil type. You should only winterize calla lilies outdoors in well-draining soils, as rhizomes sitting in wet soil over winter risk rotting. Even in warmer climates, if you don't have free-draining soil, it is safer to lift and overwinter tender bulbs indoors to reduce the risk of losing them to rot.

To winterize calla lilies in situ, stop watering plants in mid-fall to encourage them to enter dormancy. Once the foliage yellows and dies back, cut back the calla lily foliage to ground level and apply a four-inch thick layer of mulch to the tender plants. This mulching layer provides essential insulation to the rhizome against cold temperatures, and compost, straw, or bark are all suitable types of mulch to use.

It may depend on when exactly plants go dormant, as you want to let them completely die back before cutting and covering, but calla lilies are usually among the best tender plants to mulch in October in warmer climates, along with other bulbs such as dahlias and canna lilies.

Come spring, carefully remove the mulch from over the plants once you see the first shoots start poking through.

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How to Overwinter Calla Lilies Indoors in Colder Climates

Gardeners in US hardiness zones 7 or lower will have to winterize calla lilies by lifting them from the ground and overwintering them indoors. The good news is that it is not a difficult task to prepare and store the rhizomes over winter.

Follow these five steps to overwinter calla lilies indoors, and you can replant them in spring:

1. Wait until the foliage turns yellow and dies back, usually as a result of the first light frosts, and cut the leaves back to a couple of inches above the ground with a pair of clean, sharp pruning shears
2. Carefully dig up the rhizomes with a garden fork or trowel and gently remove as much soil as possible from them. Do this with a brush, but do not wash the rhizomes, as they risk rotting during storage
3. Cure the rhizomes by placing them spaced out on a tray in a dry place with temperatures of 60 to 70°F for a week. This toughens the skin and helps ensure they store successfully over winter
4. After curing, wrap the rhizomes in newspaper and place them in a paper bag filled with a little shredded paper, coco coir, peat moss, rice hulls, or vermiculite (you can get bags of professional-grade vermiculite at Walmart). Don’t let the rhizomes touch each other.
5. Place the bag in a cool, dry location that will remain around 50ºF throughout winter

Check the rhizomes monthly throughout winter and remove any that start going mushy or showing signs of rot. If the rhizomes appear shrunken due to being too dry, lightly mist the medium in the bag. You can then replant the calla lilies in spring once the risk of frost has passed.

FAQs

What to do With Potted Calla Lilies in the Fall?

If you have calla lilies in pots as part of a container garden, these plants are simple to overwinter.

Stop watering in mid-fall, once they have finished flowering, and cut the foliage down once it yellows and dies back. The rhizomes can be kept in their pots of compost in a dry and frost-free environment, such as a garage, shed, or porch.

In late winter, repot the rhizomes into fresh potting soil for container gardening and start watering to wake them from their winter dormancy.

Calla lilies multiply as the underground rhizomes naturally develop new buds and expand. You can divide plants by separating the rhizomes and cutting them into sections. As long as any section has buds, it can grow into a new plant to enjoy. You can divide calla lilies during their dormancy period, which will help prevent overcrowding that can affect the quality of the blooms.