The calla plants are perennial herbaceous species, originating in Africa, belonging to the family of the aracee and the genus of the zantedeschie; they produce a large rhizomatous root, from which branch out long, arrow-shaped leaves, fleshy and shiny, often covered by a dense series of white or silver dots. Ethiopian Zanthedeschia can be grown in the garden, or even as houseplants; in the second case the flowering can be stimulated at any time of the year, although in general it is more probable that home-grown calla lilies bloom in late winter or late summer. The large flowers are in fact inflorescences, consisting of long pointed spits, wrapped around themselves, to enclose a generally white spadix, which bears innumerable small white or greenish flowers. Spates are generally white, but there are hybrids and species with spates of various colors, from green to yellow, from red to pink; generally every rhizome produces some inflorescences, and it is good to remove them as soon as they wither; calla lilies are often used also as cut flowers.
How to grow them
These large rhizomes are grown in a soft and rich soil, which can easily moisten but which is not subject to excessive water stagnation; generally a good universal soil is used, mixed with little sand and a little shredded bark. The calla plants seem to develop best if they are grown in small containers, so it is advisable to avoid placing a single rhizome in a large vase.
During the vegetative development they are watered very regularly, avoiding to leave the water in the saucer, but trying to always keep the soil moist; if the air in the house is very dry, place the Ethiopian Zanthedeschia vase in a vase holder full of expanded clay and remember to always leave at least a couple of centimeters of water in the container; in this way the water will evaporate constantly, increasing the environmental humidity.
Calla - Ethiopian Zanthedeschia: And after flowering?
After flowering we remove all the inflorescences; the plant will tend to decay and the leaves will turn yellow. As with most bulbous plants, calla plants also need a period of vegetative rest to be able to produce flowers again; therefore as soon as the vegetation turns yellow we interrupt the watering and place the pot in a cool and not too light place. After a few months we can start watering the Ethiopian Zanthedeschia again to stimulate the development of new vegetation and new inflorescences. Plants that grow bulbs, tubers or rhizomes use the nutrients stored in the bulb or rhizome to develop flowers during the following season; for this reason if immediately after flowering we remove all the foliage from our calla, this will have no way and time to store nourishment for the next flowering. So until the foliage of our calla is vigorous and green, we continue to water it and to provide fertilizer for flowering plants, so that the following year's flowering will be guaranteed.