Calla lilies grow from an underground root storage piece known as a rhizome. Instead of planting the calla from seeds, sections of the rhizome are sold for planting. Calla are not true lilies, but are often referred to as such because of the similarity in the flower shapes. They are suitable as houseplants year-round, but should only be left in outdoor garden beds in areas with mild winters and little freezing. Whether planting calla lilies in a pot or in a bed, these attractive plants are simple to plant for even the novice gardener.
Lay a 2-inch layer of compost over a full-sun, well-drained garden bed and till it in to the top 8 inches of soil. Alternately, fill a 12-inch-diameter flower pot with a moist potting mixture.
Sow the rhizome so the top of the root piece is 6 inches beneath the soil surface. Plant one rhizome per pot or space the rhizomes 1 to 2 feet apart in all directions in the garden bed.
Water immediately after planting. Water pot-grown calla until the excess moisture drains from the bottom of the pot. Water garden-planted calla until the bed is evenly moist but not soggy.
Lay a 2-inch layer of organic mulch, such as bark, around garden calla. Mulch prevents weeds while also retaining soil moisture.
Water just as the soil surface begins to dry, as calla do not tolerate dry conditions. Water potted calla as often as necessary and water garden beds one to two times weekly.
Fertilize calla each spring. Use a liquid houseplant food for potted calla, following package application instructions. Fertilize garden calla with 5-10-10 analysis fertilizer, following the rates recommended on the package.