Callas rise above a mound of long green leaves
image by Microsoft Office clip art , DRW & Associates Inc
Katherine Hepburn's famous line to the contrary, callas or Zantedeschia are not lilies at all but members of the "arum" family that grow from rhizomes rather than bulbs. They are grown in the United States in zone 10 but may be grown a zone or two further north with winter protection. They are also grown as greenhouse plants and houseplants. Graceful spathes grow above a mound of long arrow or heart-shaped leaves. The beautiful native of South Africa presents some problems for American and European gardeners.
Grow callas outdoors if you live in a growing zone where temperatures stay above freezing. Frost will cause them to go dormant but new growth will start as soon as temperatures warm. In some areas, callas will bloom all year around.
Grow callas further north as a tender bulb. Lift callas when you take gladiolas and dahlias up in the fall. Clean off the tubers and store them in a cool, dry place like a refrigerator. Start plants in pots inside in late winter and transplant them when all danger of frost has past. Callas should bloom in late spring.
Plant callas in full sun about 4 inches deep in soil that has lots of peat moss or other organic conditioner to hold moisture. They make fine stream side or rain garden plants because they grow in clumps like ornamental grasses and cat tails.
Plant callas where they'll get plenty of water or water them frequently---they are, after all, marsh plants. In addition to friable, light soil, they'll need extra fertilizer. Give them a "bulb fertilizer" like bone meal or a 10-10-10 soluble garden fertilizer every eight weeks. Hold back water and fertilizer when they go dormant and resume when they set up new shoots.
Leave callas in place and they'll propagate prolifically. Better still, thin them out and share them and add organic amendments to the soil before replanting; you'll be rewarded with more vigorous blooming. Change the soil in pot-grown callas every year. They will exhaust the soil completely, propagate to fill the pot and strangle themselves if they're left in the same pot for several years.