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 all regions of the UK and reseed themselves readily in the autumn. The plants grow quickly up to 90 cm (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 wild flower or meadow display.
Prepare a seedbed in fall in temperate or cooler climates. Prepare a bed by digging in 7.5 to 12.5 cm (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 12.5 cm (5 inches) high. This will enable the soil to warm up more quickly in spring.
Sow the seed at 7.5 to 10 cm (3 to 4 inch) intervals 1.2 cm (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 454 g (1 lb per 9 square metres (100 square feet) of complete fertiliser as a side dressing in spring. Larkspur that are planted in the autumn 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.
Chill the larkspur seed for seven to 14 days at a temperature of 1.67 to 4.44 degrees Celsius (35 to 40 degrees Fahrenheit). Larkspur germination does not occur in warm soils that are 23.9 degrees C (75 degrees F) 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 fridge.
Fill a seed tray with potting mix and sow the seeds 2.5 cm (1 inch) apart in February. Sprinkle vermiculite over the seeds in a thin 3 mm (1/8-inch) coating. Mist the tray and place it in an environment with a temperature of 21.1 degrees C (70 degrees F). Provide bright light.
Thin the seedlings to 5 cm (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 10 cm (4 inch) pots. Move the plants outdoors in March for hardening off. Transplant the seedlings into prepared beds in April.