Delphinium

Plant in autumn or early spring in deep, fertile, moisture-retentive soil enriched with well-rotted manure. Choose a sheltered spot in full sun, ideally backed by a wall or hedge that provides wind protection without shade. Stake tall varieties from early May using grow-through supports or individual canes — waiting until stems flop causes permanent damage. Water deeply during dry spells and feed fortnightly with a high-potash liquid fertiliser from May onwards. After the first flush finishes in July, cut flowering stems back to 15 cm above the ground and feed well to encourage a second flush in September.

Cut spent flower spikes down to a strong lateral shoot or to 15 cm above ground level after the first flush. In late autumn, cut all growth back to ground level once it has died down. Remove any weak or thin shoots in spring, leaving the four or five strongest per clump.