How to Prune delphinium 'Merlin'?
Deadhead spent flower spikes back to fresh flowering side shoots and cut back to ground level in late autumn.

delphinium 'Merlin' · Delphinium 'Merlin'
Will grow well in fertile, well-drained soil in full sun and apply a balanced liquid fertilizer every other week during the growing season. Set crown above soil. It will need shelter from strong winds; staking may be necessary. See staking: perennials and delphinium cultivation for further advice
Deadhead spent flower spikes back to fresh flowering side shoots and cut back to ground level in late autumn.