Things You'll Need
Complete fertilizer (10-5-10)
Larkspur is one of the easiest wildflowers to grow from seed. Larkspur were once in the genus Delphinium but were moved to Consolida. They are lovely flowers with spires of blue, pink, purple or white. The plants are hardy in United States Department of Agriculture zones 3 to 9 and reseed themselves readily in fall. The plants grow quickly up to 3 feet tall as annuals and bloom prolifically, dying by the first frost. Plant larkspur as part of a cut flower garden or mixed in a wildflower or meadow display.
Sowing in Fall
Prepare a seedbed in fall in temperate or cooler climates. Prepare a bed by digging in 3 to 5 inches of compost to increase the texture and nutrient value of the soil. Rake the bed free of debris and form a raised bed at least 5 inches high. This will enable the soil to warm up more quickly in spring.
Sow the seed at 3- to 4-inch intervals 1/2 inch deep. Water the bed deeply. The seeds will experience the required chilling period naturally over the winter. Germination will be quick in cool temperatures. In temperate climates, germination will take place 12 to 20 days after sowing.
Apply 1 lb. per 100 square feet of complete fertilizer as a side dressing in spring. Larkspur that are planted in fall will produce blooms in four to six months. Use stakes and plant ties if necessary to support the bloom-heavy plants. Watch for insects and spray insecticidal soaps to control pests.
Sowing in Spring
Chill the larkspur seed for seven to 14 days at a temperature of 35 to 40 degrees Fahrenheit. Larkspur germination does not occur in warm soils that are 75 degrees or more. Chilling takes the place of natural cold exposure when planting in warmer climates. Place the seed in moistened sphagnum moss sealed into a plastic bag in the refrigerator.
Fill a seed tray with potting mix and sow the seeds 1 inch apart in February. Sprinkle vermiculite over the seeds in a thin 1/8-inch coating. Mist the tray and place it in an environment with a temperature of 70 degrees. Provide bright light.
Thin the seedlings to 2 inches apart when they have a set of true leaves. Keep the tray moist and warm until the second set of leaves appears and then transplant them to 4-inch pots. Move the plants outdoors in March for hardening off. Transplant the seedlings into prepared beds in April.