While not a true lily, calla lilies produce lily-like flowers in summer gardens. Often classified as a summer bulb, calla lilies actually grow from an underground root known as a rhizome. Calla lilies are a tender perennial. They do not survive winters in areas that experience freezing temperatures. The rhizomes are usually dug up after the first fall frost in these areas and stored somewhere warmer over the winter. In areas with mild winters, calla is left in the ground year-round.
Water calla lilies as needed throughout spring and summer to keep the soil moist but not soggy. Calla require even moisture and do not tolerate dry conditions. Water when the soil surface begins to just feel dry.
Lay a 2-inch layer of mulch over the calla bed. Use organic mulch such as wood bark. Mulching prevents weeds and preserves soil moisture, especially during dry periods in summer.
Fertilize calla with a 5-10-10 analysis fertilizer in spring once they begin growing again or after replanting the rhizomes if they were dug for winter. Apply the fertilizer at the rate recommended on the label.
Lay a 4-inch layer of straw mulch over the tops of the calla in fall once the foliage dies back, if you live in a mild area and are overwintering the lilies in the bed. The straw mulch prevents frost damage in the event of a mild winter frost.
Dig up the calla rhizomes in fall after the first mild frost causes the foliage to yellow and fall over, if you live in an area with freezing winters. Place the rhizomes in a perforated plastic bag that is filled with peat moss and store in a 50 degree F basement or garage until all frost danger has passed in spring.