How to Prune bearded penstemon?
Deadhead after flowering to maintain vigour, then cut back to base in winter

bearded penstemon · Penstemon barbatus
Also known as: bitterherb; bitterweed; broom-shell flower; cod head; firecracker plant; fish mouth
Grow in fertile, well-drained soil in a sheltered position in full sun or partial shade. In cold areas, protect plant overwinter with a dry mulch. See penstemon cultivation
Deadhead after flowering to maintain vigour, then cut back to base in winter