We have found 12 plants that meet your criteria.

Chinese plumbago
Ceratostigma willmottianum Forest Blue ('Lice') (PBR) Chinese plumbago Foliage turns wonderful autumnal... £9.99 Buy
tree hollyhock (syn. Blue Bird)
Hibiscus syriacus 'Oiseau Bleu' tree hollyhock (syn. Blue Bird)... Late flowering shrub with large blue flowers £12.99 Buy
Price Pruned
rose Rhapsody in Blue (shrub)
Rosa Rhapsody in Blue ('Frantasia') (PBR) rose Rhapsody in Blue (shrub)... The closest to a... NOW £13.49 Buy
Price Pruned
common Lilac
Syringa vulgaris 'Katherine Havemeyer' common Lilac Wonderful scented lavender-purple flowers NOW £16.99 Buy
periwinkle
Vinca difformis periwinkle Perfect for underplanting in shady spots £8.99 Buy
greater periwinkle
Vinca major 'Variegata' greater periwinkle Large, bright blue flowers £8.99 Buy
periwinkle
Vinca minor 'Illumination' periwinkle A recent introduction £8.99 Buy
New
lesser periwinkle
Vinca minor 'La Grave' lesser periwinkle Gorgeous lavender-blue blooms £5.99 Buy
lesser periwinkle (syn. 'Bowles Variety')
Vinca minor 'La Grave' lesser periwinkle (syn. 'Bowles Variety')... Gorgeous lavender-blue blooms £8.99 Buy
butterfly bush
Buddleja 'Lochinch' butterfly bush Fragrant violet-blue flowers all summer £8.99 coming soon
greater periwinkle
Vinca major greater periwinkle Elegant blue-violet flowers £8.99 coming soon
lesser periwinkle
Vinca minor lesser periwinkle Superb ground cover £8.99 coming soon