Delphinium exaltum (Tall Larkspur)
This native of Eastern North America grows four to six feet tall, with a spread of one to two feet and blooms from July to September with showy Gentian blue flowers. It appreciates a little shade where it is hot and humid but, otherwise, full sun is fine. Tall Larkspur blooms when other Larkspur has long disappeared, and removing spent blooms will prolong blooming and even encourage a second bloom in fall. Tall Larkspur grows best in fertile soil, medium, well-drained moisture, and it may require staking if you are in an area prone to high winds. Best planted in groups. (Photo by NPS (http://www.nps.gov/ozar/naturescience/larkspur.htm) [Public domain or Public domain], via Wikimedia Commons). Zones 5-7.