Calla lilies, just like daylilies, are not actual lilies. These plants, also known by theirbotanical name zantedeschia, are perennials in warmer zones 9 and above.
These plants grow from rhizomes, which are shaped very much like bulbs all attached together. Many Identify the rhizomes as bulbs because of their appearance.
Calla lily rhizomes are very easy to divide.The bulb shaped protrusions can be broken off and separated from the original piece, if they are large enough.