All About Callas

The flower of a Calla is actually a half-cone shaped spathe with a pale-yellow to bright-yellow spadix. If all goes well, the flower will set green berry-like fruits that gradually turn red. The seed will not come true from hybrid cultivars, but will be true in species plants.

Species calla such as the white Zantedeschia aethiopica can grow as tall as 2-3 feet. Colorful cultivars are usually shorter (from 12-18”) and generally less hardy. If moisture levels are plentiful, the tall foliage of Z. aethiopica can add a terrific note of the tropics to your borders and beds.

Match your site to the needs of calla

Callas come from marshy habitats in South Africa, and this alerts the gardener to two major points when growing this plant: 1) It needs moisture and lots of it, and; 2) It may suffer from hardiness issues in cooler climates. During the dry season of summer in South Africa, it will often go dormant based on rainfall and moisture levels in soil – and so we must be prepared for this behavior from our plants in the United States.

In general, the colorful hybrid Callas are less hardy and more apt to go dormant quite quickly after blooming. The white species type, Z. aethiopica, can remain evergreen throughout the season in areas where the summer heat is not too punishing and the soil is moist, but still must be dug if winters are very cold.

Overwintering basics

In some areas, such as the Pacific Northwest, Callas are a regular sight in gardens and along roadside ditches, spreading with abandon and needing the judicious hand of a gardener to pull them. Most of us however don’t have this problem and must overwinter our plants (north of Zone 8).

To do this, either keep individual pots plunged in garden beds for easy removal, or dig the clumps before the first frost. As Callas usually die back in the garden, it’s easy to forget about them. By putting a marker near the clump when in flower, you can help yourself locate them for overwintering.

Keep them just-damp during the winter months to prevent desiccation in an area that stays frost-free. When all danger of frost has passed, the rhizomes can be put outside for a new growing season. Don’t forget to refresh your potting soil and/or garden soil – Callas like a rich environment with plenty of moisture-retaining organics. If a longer growing season is desired, repot earlier in winter and put in a warm (65°F), well-lit spot indoors, keeping well-watered until plants can be set out in the late spring.

A good choice for aquatic gardens

As callas are originally a marsh-growing plant, they respond well to marginal, edge of pond situations and within the pond itself, growing in rich soil in a pot weighted with gravel.

The tallest of the callas, Z. aethiopica, is particularly suited to this environment as it can be placed in up to ten inches of water. In some colder areas of the US, this is below the level of ice in the winter and here it can stay. However, it is always safest to overwinter inside or experiment with one outside/one inside if you have any doubts as to hardiness.

Boggy, wet situations can encourage bacterial disease, so keep an eye on your plants growing in pond margins and remove if disease begins to rot foliage or flowers where they meet the soil.

In pots on the deck, think about plunging pots in with other exotic tropicals and sub-tropicals that love moisture such as colocasia and canna. As the summer wears on and their companions begin to outpace them, you can remove the callas, start to withhold moisture and begin their period of dormancy.

A little bit of work for a whole lot of elegance

Because the soft, half cones of calla are a mainstay of upscale florists and still regarded as an exotic bloom, they lend a touch of sophistication to a garden or a potted container arrangement. Once you’ve mastered matching this plant with the correct growing conditions, you’ll be thrilled by the oohsand ahhs you receive.

You don’t need to let on how easy they were to grow.

About the Author: Marianne Willburn is a columnist, blogger and author of the new book "Big Dreams, Small Garden: Creating Something Extraordinary in Your Ordinary Space." Originally from California, she now gardens in Virginia – read more at www.smalltowngardener.com.

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Learn How to Grow Callas