Remove weeds, dead plants and other unwanted vegetation from the garden with a rake or shovel. Rake 2 inches of compost over the garden bed. Dig the compost into the soil to a depth of 6 to 8 inches, mixing the compost and soil thoroughly.
Sprinkle the garden with 1 inch of water to moisten the soil before planting the freesia corms. If the water stands in puddles for several hours after watering, rake the amended soil into mounds or berms at least 6 inches above the soil's surface to improve drainage or build raised beds.
Dig holes for the corms using a bulb tool or narrow-bladed trowel. The holes should be 2 inches deep and spaced 3 inches apart. Place one corm in each hole with the pointed end up and cover gently with soil.
Sprinkle the garden with water to eliminate air pockets around the bulbs. Water when the soil is dry, generally once or twice a week through the growing season, but not during the summer, when freesias are dormant.
Rake a 2-inch layer of mulch over the entire garden bed to help prevent weed growth and to maintain a consistent level of moisture in the soil. Freesias prefer moist but not waterlogged soil.
Monitor the freesias for pests as they sprout and blossom. Handpick snails and slugs in the early morning, when the leaves are still moist with dew. Rinsing the leaves regularly removes dust, which discourages thripes, while a blast of water knocks aphids and whiteflies off the leaves.
Fertilize potted freesias with a slow-release 10-12-10 bulb fertilizer. Sprinkle 1 tablespoon per square foot of soil into the pot and scratch it into the top 1 to 3 inches of soil. Water thoroughly. Reapply fertilizer every two months until the foliage dies back. Freesias planted in an amended garden bed don't require fertilizer until fall arrives. Rake a layer of well-decomposed manure or compost over the garden bed to nourish the corms through winter and spring.