We have found 12 plants that meet your criteria.

Aconitum 'Stainless Steel' Monkshood Striking metallic-blue hooded flowers £7.99 Buy
Price Pruned
Delphinium 'Blue Jay' Delphinium Showy, semi-double blue flowers with dark eyes NOW £5.99 Buy
Price Pruned
Delphinium 'Gillian Dallas' Delphinium Stunning mauve-blue flowers with a white eye NOW £7.99 Buy
Price Pruned
Delphinium 'Langdon's Orpheus' Delphinium Pretty, iridiscent blue-mauve flowers NOW £7.99 Buy
Iris 'Dusky Challenger' Bearded Iris Huge ruffled silky rich purple-blue blooms £6.99 Buy
Salvia uliginosa Bog Sage Intense blue flowers £5.99 Buy
Syringa vulgaris 'Katherine Havemeyer' Common Lilac Wonderful scented lavender-purple flowers £9.99 Buy
Agapanthus 'Lavender Haze' African Lily A new, large-headed variety £8.99 Buy
Hydrangea aspera 'Villosa Group' Rough-leaved Hydrangea Long-lasting, deep mauve flowers in autumn £10.99 Buy
Hydrangea serrata 'Bluebird' Hydrangea Distinctive blue flowers and autumn colour £8.99 Buy
Price Pruned
Solanum crispum 'Glasnevin' Chilean Potato Tree Clusters of purple flowers NOW £7.99 Buy
Price Pruned
Veronicastrum virginicum 'Fascination' Culver's Root Elegant spires of bluey-mauve blooms NOW £5.49 Buy