Delphinium ajacis. Sow Rocket Larkspur delphinium seeds in fall or in early spring, when some risk of frost is still possible. Stunning spires in shades of purple and blue grow up to 1.2m (4') tall, attracting wild and domestic pollinators. Grow this southern European native in full sun or part shade, but keep soil relatively moist. This annual Delphinium produces copious seeds and will self sow from year to year. The seeds are easy to collect and share. Alternately, simply cut the seed heads down after the flowers have faded and avoid self sowing all together. Rocket Larkspur looks amazing when contrasted with yellow or orange flowers of a similar height. Try planting it near Black-Eyed Susan Rudbeckia.
Rocket Larkspur is an annual Delphinium that is native to Europe, but now grows as a wildflower in North America.
Season & Zone
Exposure: Full sun
Sow indoors 8-10 weeks before planting out, so around late February to mid-March on the coast. Direct sow in early spring or early autumn. Seeds take 14-28 days to sprout.
Just cover the tiny seeds. If starting indoors, vernalize seeds by planting them in trays in sterilized seed starting mix. Place these inside plastic bags and refrigerate for 2 weeks. Then place them in total darkness and maintain a soil temperature of 10-12°C (50-55°) until sprouted. Once sprouts appear, place below bright light. Space or thin to 30-45cm (12-18″) between plants.
Deep, rich, well-drained, slightly acidic soil. For the most bloom potential, water well throughout the season, and feed once in the early spring. Remove spent flowers immediately after the first bloom, and feed again. When new growth reaches about 20cm (8″) tall, cut back old growth completely.