Salvia uliginosa

Commonly known as 'Bog Sage', this tall Salvia produces short spikes of clear blue flowers on branching, mostly naked, stems above slightly leathery, pointed green leaves. Naturally found in South American damp grasslands where it will flower throughout the summer.
It is ideal for the back of a moist but sunny border or add to edges of ponds. Good for bees. Height 2m. Full sun.