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

Baptisia 'Purple Smoke' (Indigo weed 'Purple Smoke'): Tall spikes of violet pea-like flowers on almost black stems, attractive grey-green foliage. Dark-grey seed pods. Hardy. Up to 1.2m

Baptisia australis (Indigo weed): Spires of lipped indigo flowers over olive-green foliage. Flowering height 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.

Centaurea 'John Coutts' (Knapweed 'John Coutts'): Large almost fluffy soft pink flowers over green, slightly felty foliage with white undersides. To 40cm. Hardy. [Collect Only]

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

Euphorbia characias (Spurge): Evergreen perennial with blue-green leaves and lime-green flowers in early summer. Long-flowering. May self-seed. Prefers a sunny spot. [Collect Only]

Euphorbia characias subsp. wulfenii (Mediterranean spurge): Evergreen perennial with blue-green leaves and vibrant lime-green flowers in early summer. Prefers full sun. Hardy to about -10C, but not for long periods. Up to 1.2m. [Collect Only]

Geranium pyrenaicum 'Bill Wallis' (Mountain cranesbill 'Bill Wallis'): Masses of tiny purple flowers, good for ground cover

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 racemosa 'Snowflake' (Catmint 'Snowflake'): Compact variety of catmint forming mounds of silvery-green foliage and masses of clear white flowers. Loved by bees. Hardy. Up to 45cm.

Nepeta sibirica 'Souvenir d'Andre Chaudron' (Catmint 'Souvenir d'Andre Chaudron'): One of the largest flowers and more upright growth than other catmints. Aromatic lance shaped leaves. Hardy. Up to 45cm. [Collect Only]

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.

Persicaria affinis 'Darjeeling Red' (Knotweed 'Darjeeling Red'): Semi-evergreen mat-forming perennial with green narrow leaves that turn bronze over winter. Spikes of pink poker-like flowers which darken with age.

Sedum spathulifolium 'Purpureum' (Purple stonecrop): Mat forming, fleshy purple rosettes with an attractive grey cast when young. Yellow flowers in summer.