Delphinium ajacis aka Larkspur

Delphinium ajacis belongs to the buttercup family, Ranunculaceae. It is an annual: it completes its growth within one year. Its common names are annual larkspur and rocket larkspur. The RHS uses the name Consolida ajacis. It grows wild from southern Europe to the western Himalaya and Central Asia. It grows in temperate regions. It is not native to Britain or Ireland.

The plant grows upright, with a shape like a column. It has feathery green leaves. These are deciduous: they fall rather than stay year-round. Garden height ranges from about 1.6–3.3 feet [0.5–1 metre]. Its spread ranges from about 0.3–1.6 feet [0.1–0.5 metres]. It blooms in summer, from June to August. Most flowers are deep blue. Pink and white flowers also occur. Some have a mix of blue and pink. The flowers make it useful for summer beds.

Grow annual larkspur in full sun, in soil that drains well. The RHS lists chalk, loam and sand as suitable soils. It favours a neutral or alkaline pH. Choose a sheltered spot facing south, east or west. The stated soil moisture range is dry to moist. Missouri Botanical Garden rates its water needs as medium. The RHS gives it a UK hardiness rating of H6. Missouri Botanical Garden lists USDA zones 2–11. These ratings do not mean it is a long-lived plant. It still completes its growth within one year.

Grow new plants from seed at several times of year. Sow in early autumn, then prick out seedlings in early spring. You can also sow under cover in early spring. For outdoor sowing, you can wait until late spring. The RHS says it needs no pruning. Missouri Botanical Garden rates its care needs as low. Both sources report few serious problems with pests or disease. Powdery mildew can still occur, despite those broad reports.

Annual larkspur suits flower borders and cottage gardens. It also suits informal planting. The RHS lists courtyard, city and wildlife gardens as uses too. You can use its flowers in fresh or dried displays. Cut stems when just the lowest buds have opened. This brings its summer flowers indoors as well as outdoors. The supplied evidence gives no details on edible parts for this species. Nor does it give details on its toxicity.