How to prune lobelia siphilitica

Deadhead through late summer; cut to ground in autumn. Cut spent flower spikes back to a leaf node or lateral shoot during the season. After all flowering ends, cut stems to soil level. Protect basal rosettes from slug damage over winter but do not remove until spring growth begins.

Deadhead regularly; annual cutback in autumn. Lobelia siphilitica (great blue lobelia) responds well to deadheading to extend its late-summer display. Remove spent flower spikes down to a leaf node to encourage lateral branching and secondary blooms. After the final flush in autumn, cut plants to the ground. Overwintering basal rosettes should be left until spring.

Cut spent flower spikes back to a leaf node or lateral shoot during the season. After all flowering ends, cut stems to soil level. Protect basal rosettes from slug damage over winter but do not remove until spring growth begins.