Centaurea montana (Perennial cornflower): Large blue flowers in early summer, repeated later in year if cut back. Very attractive to bees. To 50cm. Hardy

Geranium 'Alan Mayes' (Cranesbill 'Alan Mayes'): Long flowering geranium with bright blue flowers with purple veining. Clumps of hairy green leaves, turning red in autumn. Hardy. Up to 45cm.

Geranium 'Brookside' (Cranesbill 'Brookside'): A reliable, robust variety with large rich blue flowers over a mound of deeply divided leaves. Height to 45cm. Hardy

Geranium 'Orion' (Cranesbill 'Orion'): A dome of deeply divided foliage, smothered in large blue flowers from early summer onwards

Nepeta racemosa 'Walker's Low' (Catmint 'Walker's Low'): Forms neat mounds of silvery green foliage, topped with masses of lavender blue flowers in early summer. Up to 40cm. Hardy.

Polemonium reptans 'Stairway to Heaven' (PBR) (Jacob's Ladder 'Stairway to Heaven'): Superb variety with attractive variegated foliage and lavender blue flowers. To 50cm. Hardy