Verbascum ‘Blue Lagoon’ – The world’s first ‘true-blue’ Verbascum (tinted like Meconopsis or Blue Himalayan Poppy) with purple centers accented with a thin white halo. It blooms from late May to August (with deadheading) on tall stems that rise over a basal rosette of deep green leaves. Best in full sun with good soil drainage. Grows 30″ high by 12″ wide. Zone 6.
Dracocephalum argunense ‘Fuji Blue’ – The tubular periwinkle-blue flowers of this perennial are very Snapdragon like, with the lip being accented with pale blue. These are borne on short stems from June through to August over a compact plant with linear mid green leaves. Dragon’s Head is a long-lived perennial with few problems. Grows 12″ high by 10-12″. Z5.
Catananche caerulea – Cupid’s Dart is an old-fashioned cottage garden favourite and bears lavender-blue flowers that emerge from papery buds from midsummer to autumn. This native of southern Europe works well as filler between other sun-loving perennials such as Rudbeckia, Coreopsis and Echinacea. Makes a good dried flower. Grows 18-30″ high by 12″ wide. Zone 4.
Corydalis x ‘Sapphire’ – This cross of Corydalis cashmeriana and C. flexuosa bears clusters of highly fragrant electric blue flowers (with some white highlights) from May through to August. These sit above pale green fern-like leaves that somewhat resembles Bleeding Heart foliage. Thrives in open shade with soil that is evenly moist. Grows 12-14″ high by 10-12″ wide. Zone 6.
Campanula glomerata ‘Freya’ – The bold terminal blooms of ‘Freya’ are an eye-catching purplish-blue but with about 2/3 of the entire plant being covered by flowers. It blooms from late spring through to midsummer with clusters of star-shaped blooms. The coarse dark green leaves form a tidy basal mound. Grows 16-18″ high by 12-18″ wide. Hardy to zone 3.