Despite their common name, callas are not actually lilies, nor are they related to lilies. Callas are more closely related to plants such as caladium. Black and white varieties are only two of the several colors of the calla rainbow.
The white portion is the spathe and the yellow part is the spadix.
Calla lilies don’t display their color on the flower, like most flower species. The spathe (the trumpet-shaped, colored part of the plant) is more like a leaf, with a thin spadix in the middle that possesses the tiny true flowers.
Calla lilies don’t actually have a true black variation. The black flowers actually are a deep, dark purple that resembles a black color.
Plant black or white callas in full sun during fall or spring. The soil should be rich with humus and organic material, as well as moist. Although they do best outside, callas can be grown in sunny, indoor locations.
Temperatures less than 25 degrees Fahrenheit can damage calla rhizomes. In areas that have cold winters, dig up the rhizomes before below-freezing temperatures arrive. Store them in vermiculite, either in a plastic storage container or bag with holes for air circulation.