Butterfly bushes are no brainer plants. You cut them back to about 10 - 12 inches in early spring and then let them do their thing. They'll shoot up 5 - 6' in a season and send out a continuous supply of spiky flowers in shades of white, pink, magenta and purple. And if you plant them, they will come. Butterflies really do love butterfly bushes.
Note: Butterfly Bush is invasive in some areas, such as the Pacific NW. Check with your Cooperative Extension to see if you should be planting Buddleia in your area.
Buddleia davidii 'Potters Purple' (USDA Zones 5 - 9, 6' x 4' Purple Blossoms: July - Oct.)
- Vitex agnus-castus (Chaste Tree) 'Colonial Blue' (USDA Zones 5 - 11, 4' x 3', Purple Blooms: July - August)