When to Sow Calla Lily Seeds in Southern California

Soil Temperature

• Sow calla lily seeds in early to midspring in Southern California when the soil is getting warmer by the day. Calla lily seeds germinate readily at 70 degrees Fahrenheit. Check your soil temperature using a soil thermometer, pressing the thermometer into the top 4 inches of the soil. Test in the morning or evening to get an accurate reading. Calla lily seeds take two to thee weeks to germinate.

Planting Outdoors

• Plant calla lily seeds in a sunny or partly shaded garden bed where you can keep the soil consistently damp. Plant them shallow, no more than 1/4 inch deep, spacing the seeds 3 or 4 inches apart. Later in the season, as they mature, you can thin the seedlings to a 12-inch spacing. After planting, cover calla lily seeds loosely with soil and then water until the area is damp 4 inches deep. Follow up with water whenever the top of the soil starts to dry out.

Sowing Indoors

• If you don't want to wait for spring, you can sow calla lily seeds indoors in late winter anywhere in Southern California. Use 3-inch-diameter pots filled with seed-starting mix. Plant the seeds 1/4 inch deep and keep them moist through germination and early development. A warm porch or greenhouse with a consistent temperature of 70 F or warmer makes a perfect seed-starting nursery. You can also use a heating pad under the pots to help keep the soil temperature at 70 F.

Harvesting Seeds

• Calla lily flowers turn into clusters of seeds covered with green fruit-like flesh that turns yellow-orange as it ripens. To harvest the seeds, cut the seed head at the soil line when it matures. Break apart the seed head and then put the seeds in a colander. Rub and rinse them under water until the seeds are clean, then put them on a paper towel to dry. Once dry, you can store calla lily seeds until spring planting.

Southern California

• Southern California has a wide range of growing conditions from frosty USDA zone 6 in the mountains to frost-free zones 10 through 11a along the coast. Calla lilies grow reliably in USDA zones 8 through 10. In colder parts of the state, keep calla lilies in containers and overwinter them indoors. In zone 11, summers get too hot for calla lilies to thrive, but if you want to give them a try, plant in a cool partly shaded part of the garden.