Amsonia tabernaemontana (Blue dogbane): Starry blue flowers on strong stems with willowy green leaves. Hardy. Up to 90cm.

Aster macrophyllus 'Twilight' (Syn. Eurybia x herveyi): Lavender-blue flowers with a yellow centre in late summer. Mildew-resistant foliage. An earlier flowering variety. Height to 1m.

Catananche caerulea (Cupid's dart): Masses of papery lavender blue flowers held on wiry stems all summer. Seed heads turn silver in late summer. Good dried flower. Up to 60cm.

Catananche caerulea 'Major' (Cupid's dart 'Major'): Masses of papery blue flowers held on wiry stems all summer. Seed heads turn silver in late summer.

Linum perenne 'Blau Saphir' (Syn. L. perenne 'Blue Sapphire') (Perennial flax): Slender wand like stems, topped with open faced blue flowers in summer. To 30cm. Hardy.

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.

Veronica austriaca 'Crater Lake Blue' (Speedwell 'Crater Lake Blue'): Vivid blue spikes above a mound of green foliage.To 30cm. Hardy.