Calla lilies are native to Africa and, according to the University of Illinois, are not true lilies. They are herbaceous flowering plants that cannot survive winter in the ground outdoors. The plants grow from a rhizome, similar to a bulb, much like irises. Calla lilies grow to about 30 inches in height, and the flowers are shaped in the form of a funnel. While the white flowers are the most fragrant, calla lilies also come in pink, red and yellow.
The bulb-like structure of calla lilies grows well in a planter or in the ground in warm weather. Calla lilies may be transferred indoors at the first freeze and replanted outdoors each spring. If left in the ground, the plants are considered annuals because the roots will die when frozen. The flowers bloom in the late spring and throughout the summer. After the first freeze, the rhizomes should be dug up and allowed to dry before being moved indoors or to a warm, moist spot.
Calla lilies prefer full sun and perform well in soil that stays moist. They will bloom in the summer in partial shade, especially when the soil remains evenly wet throughout the season; calla lilies grow well beside a pond or other body of water. The rhizomes, or bulbs, look like small potatoes and grow well when planted about 1 inch deep. Rhizomes should be spaced about 1 to 2 feet apart. They provide a lush summer garden when planted with other summer-flowering plants.
While calla lilies grow well outdoors in the summer and provide yearlong blooms indoors, the flowers also make popular cut flowers in arrangements. White calla lilies are popular in floral arrangements for weddings and special occasions. The flowers do not have individual petals and make appropriate gifts for anyone ranging from business associates to friends and lovers. ProFlowers has a popular pink potted calla lily that can be enjoyed indoors and later planted outside for continued enjoyment or remain as an indoor plant.
Calla lilies are toxic and should not be kept where children or animals can get at them. The roots are the most dangerous part of the plant, though the entire flower is poisonous. Symptoms of calla lily poisoning include nausea, diarrhea and vomiting. When ingested or placed in the mouth, the oxalic acid in the plant causes burning and swelling of the mouth, tongue and throat. If the acid gets in your eyes, it can cause pain and swelling.