Classification of the Calla Lily

Genus

The dramatic plants with the blooms that resemble porcelain are not lilies at all but members of a tropical genus called Zantedeschia, named for an Italian botanist, Giovanni Zantedeschi. The genus is part of the larger family Araceae, which includes caladiums, anthuriums, peace lilies and dieffenbachia. The genus of the calla lily, also known as arum lily, after its biological family, includes six subgroups, or species, including four -- aethiopica, albomaculata, elliottiana and rehmanii -- commonly grown in summer gardens, says Dr. Leonard Perry of the University of Vermont.

Each species includes cultivars, or cultivated varieties, that have been hybridized to grow in specific areas or under certain conditions. 'Little Gem,' a 12- to 18-inch-tall white cultivar that dates to 1890 might have been the plant that complemented Hepburn's lanky grace. It is a member of the aethiopica species. Other cultivars and species feature yellow, green, peach, pink, purple, maroon or red blooms, some lighter or different colored on their interior and some with spots or highlighted edges. Plants grow to 30 inches.

Flowers grow on thick stalks that rise above clusters of long, sword- or arrow-shaped foliage. Similar to other arums, the calla lily "bloom" is actually a spathe -- a specially shaped leaf that shelters the inflorescence, which is a collection of tiny flowers crowded onto a long spadix. Unlike relatives such as the peace lily, whose spathe obviously is a specialized leaf, the calla lily's spathe wraps all the way around the spadix much as a stole or collar on a blouse that folds over on itself, displaying the interior at its top.

Natives of tropical and semi-tropical areas in south and east Africa, Calla lilies grow as perennials in USDA Plant Hardiness Zones 9 and 10. They grow from rhizomes and require moist, well-drained organic soil. Forest floor natives, they thrive in dappled sunlight to part shade but will tolerate sun where summers are cool. In tropical zones, Calla lilies grow as marginal aquatic perennial plants, tolerating up to 4 inches of water. They grow as tender perennials in northern zones where they are planted in spring and bloom in midsummer. Calla lilies bloom midwinter in their native range and florists grow them in pots for year-round blooms.