Agastache 'Blackadder' (Giant hyssop 'Blackadder'): Bright blue flower spikes and aromatic foliage - very attractive to bees. To 1.2m. Hardy

Agastache rugosa 'Liquorice Blue' (Korean mint 'Liquorice Blue'): Spikes of warm blue lipped flowers from late June onwards. Very attractive to bees. Aromatic foliage. To 1.5m. Hardy in light soils. [Collect Only]

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.

Baptisia 'Indigo Spires' (Indigo weed 'Indigo Spires'): Spikes of violet-blue pea-like flowers with a yellow edge above a mound of grey-green foliage. Long flowering. Hardy. Up to 1.2m

Campanula portenschlagiana 'Resholdt's Variety' (Wall bellflower 'Resholdt's Variety'): Carpeting alpine with brilliant blue flowers over a long flowering period in summer.

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.

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

Eryngium bourgatii Graham Stuart Thomas's selection (Sea Holly Graham Stuart Thomas's selection): Spiny, violet blue flowers in summer of even spinier blue-green leaves with white mid-ribs.

Nepeta 'Six Hills Giant' (Catmint 'Six Hills Giant'): A vigorous sun lover which will soon make a generous clump. Spikes of tiny purple flowers over aromatic grey/green foliage.

Nepeta grandiflora 'Summer Magic' (PBR) (Catmint 'Summer Magic'): A more compact, upright growing variety of Catmint with aromatic grey foliage and spikes of lavender blue flowers. Hardy. Up to 35cm.

Nepeta x faassenii 'Kit Cat' (Catmint 'Kit Cat'): A compact variety of catmint making a neat mound of aromatic green foliage and clusters of lavender blue flowers. Hardy. Up to 30cm.

Scabiosa caucasica 'Stafa' (Scabious 'Stafa'): A darker blue form of the classic large cornflower blue frilled scabious flowers over lance-shaped grey-green foliage. Height to 60cm. Hardy.

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