Clear an area in partial sun of all weeds, debris and grass. Calla lilies prefer morning sun and late afternoon shade. The soil should be moist to wet, since calla lilies like plenty of water.
Loosen the soil to the depth of 12 inches with a shovel. Spread 3 to 4 inches of compost or manure on top of the soil. Mix this organic material into the loose soil.
Mix 20-20-20 slow-release fertilizer into the top 6 inches of soil. Rake the soil smooth and level. Dig a hole 4 to 6 inches deep with a hand trowel. Place the calla lily rhizome, which looks like a small potato, in the hole. Adjust the depth of the hole so the top of the tuber is only 2 inches from the surface.
Fill the hole with soil and do not compact it down over the top of the tuber. Plant the rest of the calla lilies 12 to 24 inches apart. Spread 1 inch of mulch-like wood chips over the calla lily planting area. The mulch will preserve the moisture in the soil.
Sprinkle the area with water until the moisture reaches the depth of the tubers. Keep the calla lily bed moist. When the soil under the mulch begins to dry out, water again.