When considering everything you want to know about calla lilies, perhaps the most important thing to keep in mind is that even though they are grown as ornamental plants in many areas, they are also considered weeds in some locations. Calla lilies refer to a group of six species in the Zantedeschia family that are native to tropical and subtropical areas in Africa. These perennial flowers typically grow 12 to 24 inches tall, although some grow taller than 4 feet. Calla lilies (also known as arum-lilies) are technically classified as aroids, not lilies, meaning they are related to jack-in-the-pulpit and caladium.
Calla lilies produce a showy, trumpet-shaped, flower-like leaf called a spathe, which can be white, yellow, red, maroon, pink or purple. Some cultivars of calla lilies feature spotted spathes. The trumpet-shaped spathe holds the spadix, a finger-like structure that holds the smaller inner flowers, which are the plant's true flowers. Calla lily plants have dark green arrow-shaped leaves, which may appear flecked.
Calla lilies grow best in full sun or up to 25 percent shade. They bloom poorly if grown in excessively shady locations, although very hot sunlight can also damage the flowers. Calla lilies prefer moist, rich soil. You should plant calla lily bulbs about 2 to 4 inches deep in the soil, allowing 12 to 18 inches between the bulbs. They grow well in raised beds. Calla lilies can also be grown in containers inside, especially smaller varieties, if they are placed in a sunny location.
Calla lilies bloom in late spring or early summer and bloom for about a month. In some locations, calla lily bulbs (technically called rhizomes) must be dug up and stored inside during the winter and then replanted. Store calla lily bulbs in a dark, dry location kept between 50 to 60 degrees. If possible, cut holes in the bag to allow air exchange. Handle bulbs with care; damaging the rhizomes will damage the flowers. In other locations, calla lily rhizomes can be left in the ground, where they will re-sprout the following year.
Calla lilies sometimes develop leaf spot, root rot, bacterial soft rot and plant viruses. The plants are considered hardy in USDA hardiness zones 9, 10 and 11, and are considered hardy with mulch in hardiness zone 8. They can be grown in containers in hardiness zones 2 through 8.
Calla lily plants are poisonous to humans and animals, especially the roots. The plants contain oxalic acid and a protein called asparagine, which may cause vomiting, nausea, diarrhea, burning in the mouth or throat, mouth and tongue swelling and eye pain, redness, burning or swelling. In severe cases, calla lilies can cause throat swelling severe enough to cause breathing problems.
If a person has consumed part of a calla lily plant, call 911 or the National Poison Control Center (1-800-222-1222). Wipe out the person's mouth with a clean cloth soaked in cold water. Give the person milk unless they are vomiting or having trouble swallowing, or unless a healthcare professional advises you not to.
Do not let children or pets play with or near calla lily plants, especially if unsupervised. Calla lilies have reportedly been fatal to humans and livestock.
Keep the aforementioned facts in mind should you decide to plant calla lilies, especially the information regarding the plant’s poisonous nature.