Temperature Requirement for Growing White Calla Lilies

Hardiness

• Calla lilies are hardy in the ground where winter temperatures don't drop below 15 degrees Fahrenheit -- U.S. Department of Agriculture climate zones 8 through 10. In colder climates, treat them like dahlias or gladiolas and dig the rhizomes in fall to store over the winter. In climates where they are hardy, they are often considered a weed, because they multiply and spread quickly.

Indoors

• Calla lilies are sold as houseplants, and they do very well indoors in a sunny south or west window. They bloom for about a month in midsummer and then go dormant. After the leaves brown, let the plant rest. Keep the soil moist but not wet. New growth begins in spring.

Planting

• Plant calla lilies in full sun or part shade, in rich soil amended with plenty of compost. Set the rhizomes 6 inches deep and about 2 feet apart, as the plants will form large clumps over time. Top with mulch about 1 inch thick. Calla lilies also grow well in potting soil in containers. The smaller hybrids make colorful annuals for window boxes and porch or patio pots and come in pink, purple, orange, peach, yellow, lavender and white.

Care

• Steady moisture is essential for calla lilies. In their native habitat, they grow in boggy or wet areas near streams or in ponds. Fertilize every spring with an organic fertilizer formulated for flowers. After frost kills the foliage, leave it in place as winter protection in mild climates, or dig the rhizomes, let them dry for about a week in a warm location, then store them in vermiculite, peat moss or perlite in a cool, dry place.

Toxicity

• All parts of the calla lily plant are toxic, as the plant produces oxalic acid, the same toxin present in rhubarb leaves.