Veronicastrum virginicum 'Cupid' is a Culver's root with architectural lilac-blue blooms on tall rigid stems.

Veronica 'Tidal Pool' has darling blue flowers with white eyes and lush ground covering foliage.

Veronica 'Waterperry Blue' is a great evergreen speedwell with burgundy-flushed green foliage and charming lavender flowers.

Viola corsica, the Corsican violet, offers masses of violet-blue flowers with purple whiskers and tiny yellow centres.

Viola pedata is a lovely little violet with very cool, dissected foliage that looks like a bird's foot.

Viola Magnifi Scent 'Blue Sails' is a hardy viola with beautiful blue and white flowers and a strong, sweet violet fragrance.

'Blue Moon' is an extremely fast growing and super hardy Wisteria for zone 3(!) that blooms up to three times a year.