Marin IJ Articles
May 19, 2008
Although we call it a lily, the calla is not a true lily, but an arum like the Dracunculus vulgaris or dragon lily, which is similar to the calla blossom in form, but dramatically different in color. Under the right conditions the calla can be invasive and is under consideration, but not listed, as a pest by the California Exotic Pest Plant Council.
On the other hand, Pam Peirce lists it as a beautiful, but tough, survivor in her book, Wildly Successful Plants Northern California. Its name means “splendid beauty” and has long been a popular subject for the camera and painter alike and is used as an architectural motif. The calla is an excellent cut flower often used in bridal bouquets and for funerals. They last best if cut before they shed their pollen.
The common calla (Zantedeschia aethiopica) is the one familiar to most of us and has a white flower bract (spathe) that surrounds a central spike (spadix), which is tightly covered in the tiny true flowers. It grows from a rhizome type of bulb. It is native to South Africa, which has a Mediterranean climate similar to our own.
The calla comes in other colors, but none is as easy to grow as the common variety which is tolerant of most soils and thrives in wet, even boggy, conditions. Callas will grow in drier soil as well, but the plants tend to be smaller and are not so rampant, in my experience. Plants grow in full sun, but in hot-summer areas they do better with a bit of shade. My callas tolerate a western exposure because temperatures are moderated by closeness to the Bay. Because the calla is so adaptable it survives a certain amount of neglect.
Callas can be planted in the spring to early summer or in the fall. In our climate bulbs need not be dug up for winter storage. Set the rhizomes four inches deep and about a foot apart. They will thrive in an organically rich, slightly acid soil. Fertilize lightly during the growing period. Usually dormant in winter, they will not go dormant if the soil is kept damp all year. I prefer their dormancy in my garden because they are replaced with Hostas, a true lily, through the fall. The best time to dig and replant the common calla is from July into fall, but it will usually transplant any time of the year.
Peirce advises pulling the whole flower stem out when the flower begins to turn brown. As the leaves yellow pull or cut them off. Check for snails. They love callas and I sometimes find them nestled in the spathe.
If you want to get rid of callas you can prevent seed formation by removing spent flowers. When dividing plants try to avoid breaking up the rhizomes and then remove the yellowish rhizome buds or you will have small plants popping up as long as they remain in the ground.
The calla is listed as toxic by the California Poison Control System. The sap contains oxalate crystals that can irritate the skin or mouth and tongue and cause a swelling in the throat and consequent breathing difficulties. Peirce cautions the sap will also stain clothes, but the brown stain will only appear after the clothes have been washed.
The calla comes in a variety of colors ranging from black, lavender, red, peach yellow to plum as well as hybrid mixes. Prices can range from $8.00 to $21.00 a bulb. An Australian grower charges $14 a bulb for a dark calla dubbed “Hot Chocolate,” a 2003 winner at the Chelsea Garden Show and Best New Flower at the Atlanta Show in 2004. This variety produces a high number of flowers per bulb and is disease resistant. There is even a scented calla (Zantedeschia odorata) with a perfume similar to the freesia.
Is it a prize or a pest? You decide if the calla has a place in your garden.