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.

Ceratostigma plumbaginoides (Plumbago, Hardy plumbago, dwarf plumbago): Brilliant blue flowers in later summer over foliage which turns redder as winter approaches. Stunning ground cover plant for sheltered spots. Not fully hardy in colder parts of UK. To 20cm. Frost-hardy

Eryngium x zabelii 'Big Blue (Sea Holly 'Big Blue): Large electric-blue thimble-shaped flowers with a spiky collar and silver-green foliage. Long flowering and bee-friendly. Hardy. Up to 75cm

Salvia patens 'Cambridge Blue': Beautiful Salvia with pale blue two-lipped flowers flowering in late summer. Needs a sunny, sheltered position and protect with mulch.To 1m.

Salvia uliginosa (Bog Sage): Branched stems of clear blue flowers and lance-shaped leaves. Needs a sunny spot but with moist soil. Late flowering. To 2m.