In USDA zone 3, hostas dominate the list of those species able to tolerate shade and still generate a purple flower. Among the cultivars fit for the cold of this particular zone are Sugar Plum Fairy, Golden Tiara and Lemon Lime. Different species of hosta for the zone include the narrow-leafed hosta, which blooms from July through September and has the long stems typical of hostas upon which the purple-violet flowers develop. Red-purple is the color of the flowers of some cultivars of the hybrid primrose called primula. Wanda is a type with April flowers, growing to 6 inches tall in zone 3.
Disanthus features October purple flowers, growing in the shade and surviving in environments as chilly as those of USDA zone 5. This deciduous Asian shrub grows to 10 feet high and develops bright fall foliage as it blooms, giving it a double appeal. The Korean azalea and Korean rhododendron also have purple flowers and handle shady sites. Perennial plants such as corydalis, fumewort and bishop's hat like shade and provide purple flowers. Hellebore is a perennial for zone 5 with several purple-flowering types, such as Royal Heritage, to choose from. Lilies, such as the toad, wood and spider lily, also fit this description.
In some instances, the foliage of a purple-flowering plant for shade has at least as much ornamental value as the flowers do -- and sometimes more. Dark Vader is a type of lungwort with purple flowers, but the large green leaves with silver spots are what get a passerby's attention. This plant grows in USDA zone 7, as does the cultivar of evergreen azalea called Mrs. Henry Schroeder. It grows to 3 feet, with purple-pink flowers in May. Zones warmer than zone 7 are too hot for this plant. Other plants with purple blooms for zone 7 shade include Jack-in-the-pulpit and arisaema.
Keep the spring vetch out of full sun, or the plant suffers damage. This species of perennial, appropriate for USDA zone 9, grows to 12 inches high and turns out purple flowers in early spring. Use the toad lily in zone 9 shade and woodland gardens. This plant has a white flower, but it has a dense covering of purplish spots on it. Other species appropriate for zone 9 shade with a purple-flowering effect include certain hellebores, spider lilies and primulas, such as the Wanda Elaine cultivar.