Calla lilies produce trumpet-shaped flowers atop tall stems. They bloom for most of the summer months, providing elegant color to flower gardens. These plants grow from a swollen root called a rhizome instead of from seed. New rhizomes are available at garden centers in spring, or you can divide the rhizomes of existing plants and grow them into new callas.
Tender calla lilies cannot tolerate prolonged frost, which is why the roots must be dug and stored indoors each fall. Wait to plant outside until after all frost danger has passed in spring. While a light frost usually won’t kill the plant, it can delay blooming.
These flowers thrive in moist, rich soils where they receive full sunlight. They can tolerate some afternoon shading if a full sun bed is unavailable. Avoid planting in areas prone to standing water, either after rain or irrigation. Soils naturally rich in organic matter provide the correct amounts of drainage and moisture retention. Add compost or other organic amendments to poorer soils to improve their quality prior to planting.
Planting the rhizomes too deeply can inhibit blooming or cause the roots to rot. The rhizomes resemble small potatoes with growing buds along the top surface. Plant the rhizomes with the buds facing upward. The top of the rhizomes should set no more than 3 to 4 inches beneath the soil surface. Calla lilies produce full, lush foliage so they require space to spread. Set the rhizomes 12 to 18 inches apart in all directions to provide this space.
Water the calla lilies immediately after planting, moistening the top 8 inches of soil. Spread a 2-inch layer of mulch over the bed to prevent weed growth and to help retain moisture in the soil. Calla lilies grow and bloom best when provided with regular applications of a soluble, balanced fertilizer. Make the first application after planting then reapply the fertilizer once monthly throughout summer.