Single roots.
Once established will make a large clump producing light blue flowers.
ummer-flowering perennial plants, grown for their showy flowers, commonly in shades of blue and purple, but also white and pink. They thrive in any well-drained, sunny position in the garden, or grow these beauties in containers. All flower best when the clumps become mature. 
Feed in spring with Tomorite.
Height 30-36″ (75-90cm)