Calla lilies are native to Africa and are hardy in the southernmost parts of the U.S. Northern gardeners can grow calla lilies successfully, though, by bringing the bulbs indoors before the first hard frost. Proper storage is essential to avoid disease and rot. Brown tips usually indicate a disease problem or improper growing conditions.
Lack of Water
Calla lilies thrive in moist or even wet soils. They're often found along streams and woodlands in their native areas, where they're considered weeds. Calla lilies may develop brown tips if allowed to dry out, especially in dry climates. Water the soil frequently to keep it moist and mulch it with 2 to 3 inches of wood chip mulch.
Several viruses affect calla lilies and may cause distorted leaves, brown tips or mottled leaves. These viruses are spread by aphids, and once the plant is infected, the only option is to destroy it. The best strategy is to control aphids early. Wash the plants with a steady stream of water or treat them with insecticidal soap or horticultural oil. Apply these chemicals early in the morning or in the evening because they can burn the plant's leaves when applied in midday.
Although calla lilies appreciate wet soils, the dampness may sometimes encourage the growth of bacteria or a fungus. These pathogens can cause the bulbs to rot. The calla lily may develop stunted growth, brown tips or the entire crown of the plant may fall apart. Remove infected calla lilies so the pathogens don't spread to other plants.
In cold climates, treat calla lilies as annuals, or dig them up after the first light frost or when the leaves turn yellow. Treat them carefully because nicks or cuts in the bulbs can open the plant up to infection that may cause brown tips the following season. Cure the bulbs for two to three days in a warm, dry room. Store the bulbs in vermiculite at 50 degrees Fahrenheit. Proper storage ensures healthy, disease-free bulbs.