How to Prune brown foxtail lily?
Unless seeds are required, spent flower spikes can be cut down at the base

brown foxtail lily · Eremurus fuscus
Grow in fertile, free draining soil, in a sunny position with plenty of root space. May need staking in windy sites. Mulch with garden compost in autumn, but avoid covering the crown. Needs winter cold to flower, but protect young spring growth from frost. See eremurus cultivation for more detailed advice
Unless seeds are required, spent flower spikes can be cut down at the base