Calla: June 2020 Houseplant of the Month

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The Story Behind the Calla 

Like the anthurium and the spathiphyllum, the calla—botanically known as Zantedeschia—is a member of the Arum family (Araceae) and is characterized by its pitcher-shaped bract (spathe), now available in a wide range of colors. The actual flowers, on the tubular spike in the centre of the inflorescence, are tiny and less eye-catching. 

Calla “lilies” (left) actually look nothing like true lilies (right). Photos: www.longfield-gardens.com

Although often called calla lily, it is not, of course, in any way related to the true lily (Lilium spp.) of the Lily family (Liliaceae). It’s also called the arum lily … but so are a half dozen other plants.

The white calla ((Zantedeschia aethiopica) covers vast territories in swampy areas. Photo: brisbane.qld.gov.au

Many arums have a preference for swamps. Zantedeschia species are also swamp plants that embed themselves firmly on river banks. The different species originate from southern Africa as far north as Malawi, and often grow in places where rainwater drainage is obstructed. These are periodically saturated swampy spots, but for relatively short periods, then they dry out. The plant can easily survive subsequent long periods of drought. 

Behind the Name

Zantedeschia was originally called Arum aethiopicum or Ethiopian arum lily, although it in fact grows nowhere near Ethiopia. At that time (18th century), Africa was largely unknown and Ethiopia was commonly thought to refer to the entire continent. The plant was later renamed Calla aethiopica, “calla” being Greek for beautiful, since the plant was believed to be a close relative of the bog arum, Calla palustris, but it turned out to be only a very distant relative. Even so, the name calla clung on as a common name for the genus.

Giovanni Zantedeschi. Photo: Rudolph Hoffmann, Wikimedia Commons

However, botanists now had to find a new name for the plant. Richardia africana was also used for a while, after the French botanist Louis Claude Richard (1754–1821), but it turned it had already been used for an obscure genus of New World plants, so yet another name was needed. Finally, botanists adopted the name Zantedeschia, after the Italian doctor and botanist Giovanni Zantedeschi (1773–1846) and that name stuck. 

The simple yet singular beauty of the white calla (Zantedeschia aethiopica). Photo: Alvesgaspar, Wikimedia Commons

The first calla grown was the white calla (Zantedeschia aethiopica) and it remains popular as a garden plant in mild climates, although, due to its large size, is rarely grown indoors. Its huge white flowers became very popular with florists and soon became particularly associated with mourning. Other calla colors, though, don’t have that negative connotation.

What to Look for When Buying a Calla

Callas come in a wide range of colors. Photo: Home Depot
  • Pricing is generally based on pot size, number of flowers per plant and the plant’s volume. 
  • It is also important to consider maturity. Avoid plants showing mostly green buds, particularly during the months with low light levels. Such flowers often struggle reach their full size and coloration due to lack of light.
  • Ensure that the plant is free of pests and diseases. This includes botrytis—a fungus that greatly detracts from the decorative value—on the leaves or flower. The tubers and the plant itself can also be infected with bacteria in the form of slimy stems and rapid decline of the plant. Yellow or drooping leaves are likewise not a good sign. 
  • Callas are stored cool during shipping (8–12°C), but only for short periods. After that, they need more warmth. Beware of plants stored too long in sleeves during the shipping and storage phase, as flowers and foliage can become damp due to excessive humidity and condensation inside the cellophane, leading to disease. Only the potting soil should be damp. 
  • If you buy tubers, look for large ones. The tuber’s diameter (given in cm) largely determines the number of flowers that will be produced by each plant.   

Not for Consumption

Obviously, callas are for decoration only and not for human consumption. Like most other arums, they are toxic to people and pets and should be kept out of the reach of small children.

Assortment

Callas make great gift plants. Photo: http://www.florastore.com

The calla is most widely available in the spring and summer months. Its range has expanded considerably in recent years, so that there are many flower colors and leaf markings available. Flowers can be white, pink, yellow, orange, red, purple, green and even nearly black. Bicolors are also available. They are usually single, but can also be double. The foliage can be narrow or arrow-shaped, green or spotted with white. The most popular varieties these days are the smaller-flowered hybrids, which produce more compact plants better suited to indoor growing. 

Besides being used as a gift plant and houseplant, callas also make great garden plants and as such are often sold as dry tubers for planting outdoors in the late spring or early summer. 

Care Tips

Callas come in various sizes with green or spotted leaves.

Callas are easy to care for and can be enjoyed for a long time. 

  • Indoors, the plant requires a bright spot which is as cool as possible. This will ensure the longest flowering. 
  • The plant is undemanding in the garden and, once in bloom, can be placed in either sun or shade. The temperature must remain above 5–8 °C (40–46 °F).
  • Indoors, callas can bloom for 2–12 weeks. The plants can flower for longer outdoors, particularly when the temperatures are cool.  
  • Make sure the soil never dries out by watering regularly. 
  • Apply fertilizer every two weeks to ensure lavish flowering. 
  • Most gardeners treat cannas as temporary plants and buy new ones each year. However, they can be rebloomed by giving them a rest period during the winter, when the plant is kept dry and the leaves are allowed to die back. The tubers will produce plenty of new flowers during the next growing season. 

Display Tips

Callas adapt to many indoor decors.

Their attractive often bright colors mean that callas work very well in cheerful ‘handmade’ interiors. The plant, which already appears to be a mixture of local and exotic, looks fabulous in artisanal pots with colorful ethnic patterns. 

The Calla Lily can also be placed in a simple earthenware pot, which looks attractive on the balcony or patio (a gift idea for Father’s Day). The attractive shape of the spathe makes it a fabulous eyecatcher anywhere.

The Calla Lily also combines readily with other foliage and flowering plants.


Start a trend and grow a calla today!

Text adapted from a press release by Thejoyofplants.co.uk
Unless otherwise mentioned, photos from Thejoyofplants.co.uk.
Styling by Elize Eveleens, Klimprodukties.

Hybrid Callas in a Cold Climate

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Calla lilies (Zantedeschia spp.), which I’ll just call callas in this article, have come a long way since I first started growing them 40 years ago. At the time, all I could find were the species: the big, blustery, great white calla (Zantedeschia aethiopica), with huge white flowers and big arrow-shaped leaves on a plant 4 feet (1.2 m) or more tall or the yellow calla (Z. ellottiana), a much more diminutive plant with narrower yellow flowers and white-spotted leaves*. 

*Callas bearing translucent white dots are said to be maculate; those without dots, immaculate.

These days, though, all the local stores offer are dwarf callas, most only 1 to 2 feet (30 to 60 cm) tall. These are hybrid varieties with fairly narrow flowers and often narrower leaves as well, sometimes lanceolate, with or without white spots. The flowers come in a wide range of colors including white, pink, yellow, orange, red, purple and near black, plus bicolors. These are hybrids involving various Zantedeschia species like Z. elliotianaZ. rehmanniiZ. jucunda and Z. albomaculata.

Hybrid callas were originally developed for the cut flower trade, then only belatedly did some growers realize there might be some potential for them as garden plants.

Family Traits

Calla “lilies” (left) actually look nothing like true lilies (right). Photos: http://www.longfield-gardens.com

Although often called calla lilies, callas are not lilies, of course. Native to Africa, they belong to the Araceae family (philodendron family) not the Liliaceae (lily family). They get the common name because Linnaeus originally classed them in the genus Calla due to their similar appearance to the much hardier marsh calla or bog arum (Calla palustris), but were later moved to the genus Zantedeschia, named for the Italian botanist Giovanni Zantedeschi, in 1826. Since no one wanted to even guess at how to pronounce zantedeschia, the name calla stuck.

A leaflike spathe wraps around a finger-like spadix. Photo: http://www.amazon.in

The inflorescence is composed of a showy leaflike bract called a spathe wrapped around a central finger-like spadix that bears the true flowers. Oddly, the flowers are monoecious: the plant bears separate male and female inflorescences on the same plant. 

The plants grow from underground tubers or rhizomes. Rhizomatous types spread; tuberous types, such as the dwarf hybrids, tend to stay put.

Do note that callas are poisonous due to their high oxalic acid content. Not that many people or pets are poisoned, though, as the burning sensation caused by the first bite causes them to rapidly spit out the offending part. Still, keep them out of reach of children and pets.

Calla leaves produce guttation: drops of sap from their leaf tip that are sometimes mistaken for dew. This apparently helps relieve pressure when water starts to build up in their stems and leaves. 

Climatic Considerations

The great white calla (Zantedeschia aethiopica) can be grown outdoors year round in mld climates. Photo: jacquesamandintl.com

The hardiest calla is the great white calla (Z. aethiopica): it can be grown outdoors year round in hardiness zones 8 to 10 (sometimes 7) as long as the ground doesn’t freeze more than superficially and, in fact, has escaped from culture and become a weed in some mild temperate climates. Consider all the others to be tender plants, to be grown as annuals or brought indoors as tubers to overwinter in cold climates. 

Growing Hybrid Callas

Nice, big tubers: just what you should look for. Photo: http://www.kapiteyn.nl

Tubers are available in late winter or spring, whenever that is in your area, both in stores and by mail order. If possible, buy larger tubers (size 18- 20 or 20+). They produce more flowers and denser foliage. If you don’t plant them right away, keep them cool and dry.

You can start the tubers indoors, but no more than a month before planting out time; otherwise they’ll start to bloom indoors, probably not what you want. Or plant them directly in the garden. Wait until there is no risk of frost and the ground has warmed to about 65˚C (18˚C) before planting them out.

Hybrid callas prefer fairly warm summers and, in colder climates, will do best in full sun in a spot protected from the wind, although partial shade is quite acceptable where summers are hot. You can grow them in pots (which makes bringing them indoors in the fall simpler) or plant them in flower beds.

Unlike the great white calla, which is essentially a swamp plant and will even grow with its rhizomes under water, the hybrid varieties are subject to rot, especially as they come out of dormancy, so choose a spot with good drainage. Add lots of compost at planting: they like rich, loose soils.

Callas can be grown in the ground or as patio plants. Photo: Gardeningwithbulbs, http://www.youtube.com

Planting is a snap: just set the tubers about 6 inches (15 cm) apart (half that in containers) and 2 to 4 inches (5 to 8 cm) deep with the eyes pointing up, then cover with soil and water lightly. 

Keep them on the dry side until you see shoots appear above the ground, then maintain even moisture. Certainly, don’t allow them to dry out. 

In general, callas bloom about 60 to 90 to days after planting, thus from mid-summer to early fall; earlier if you started them indoors. Each tuber can usually produce 5 or 6 flowers.

Reblooming Hybrid Callas

This is not so simple. I personally have, at best, only modest success when reblooming hybrid callas (the species are much easier in that regard). After all, they were developed to be throw-away plants, one hit wonders: hybridizers never took “reblooming” into consideration as a serious criteria. Often, I just get foliage the second year. Even when they do rebloom, they just never seem to have the vigor and heavy bloom they had the first year. Honestly, it’s simpler to treat them as annuals and let the frost kill them, but if you do want to try and keep them going, here’s what to do. 

First, don’t skimp on the fertilizer. Throughout the growing season, fertilize regularly with soluble all-purpose fertilizer to try and plump up the tubers in view of next year’s bloom. Also, remove the flowers as they fade to keep the plant from going to seed. 

When the leaves die back in fall (or when frost has killed them), dig up the tubers or, if they are growing in a pot, just bring the whole pot indoors. Cut off the faded foliage and brush off the soil from the loose bulbs.

Cure calla tubers in warm, dry conditions before storing them away for the winter. Photo: Happy Garden, http://www.youtube.com

Callas seem to need a bit of a spell of dry heat to harden off (this is called curing), so leave pots or tubers in a warm, dry spot like a garage or tool shed for a week or so, then move them to a cool (50–60˚F/10–16˚C), dry storage area for the winter. Loose tubers can be stored in vermiculite or peat or wrapped in newspaper. As for pots, simply pile them together.

Check the tubers monthly and lightly spritz them with water if they seem to be shriveling. If the tubers are kept in pots, water just enough so the growing mix doesn’t dry out entirely. 

Then in late spring, start all over. 


Best of luck!