How to prune sea holly

Late winter to early spring for the annual tidy-up; deadhead in late summer if self-seeding is unwanted. Cut spent flower stems back to the basal rosette with sharp secateurs in late winter. If leaving for winter structure, simply remove stems once they deteriorate completely.

Once annually for the main tidy; deadhead as needed in summer. Sea Holly (Eryngium planum) needs minimal pruning. Deadhead after flowering if you want to prevent self-seeding, but the spiny, steel-blue dried seed heads are ornamentally valuable through winter. Cut stems down to the basal rosette in late winter or early spring to tidy the plant.

Cut spent flower stems back to the basal rosette with sharp secateurs in late winter. If leaving for winter structure, simply remove stems once they deteriorate completely.