Monarda x ‘Snow White’ – This 1955 introduction is still considered one of the best white Bee Balms even though the blooms are about half the size of some of the larger red cultivars. It flowers from July to September and should be watered well and mulched during dry spells to discourage powdery mildew. Good cut flower. Grows 24-32″ high by 20-24″ wide. Zone 4.
Liatris spicata ‘Floristan White’ (syn. ‘Floristan Weiss’) – A white-flowered cultivar of Gayfeather or Blazing Star with spires of bottlebrush flowers (from July to August) with short green grass-like leaves near the base. It attracts butterflies and is quite drought tolerant. Liatris can be purchased as tubers or potted plants. Grows 30-36″ high by 20″ wide. Hardy to zone 3.
Silene alpestris ‘Flore Pleno’ – A double-flowered form of Catchfly with fringed white blooms in summer (that much resemble Baby’s Breath) held on 4-6″ high stalks. It is a good choice for the alpine garden as it prefers part to full sun and gritty, well-drained soils. This Silene has deep green foliage and can be used as a small-scale groundcover. Grows 6″ high by 12″ wide. Hardy to zone 4.
Astrantia major ‘Star of Heaven’ – This Masterwort bears pincushion-shaped white and green flowers (throughout the summer) surrounded by a papery bract that resembles an Elizabethan collar. It prefers a part shade exposure and should be deadheaded regularly to promote new blooms. Long-lasting cut or dried flower. Grows 18-24″ high and wide. Hardy to zone 5.
Anemone nemorosa – Wood Anemone is an RHS Award of Garden Merit winner and native throughout much of northern Europe. It bears pure white daisy blooms of 6-7 petals with contrasting golden yellow stamens and a pale pink reverse. It spreads by vigorous underground rhizomes which makes it a good woodland groundcover. Goes summer dormant. Grows 6-9″ high. Zone 3.