The common name is chaste tree, which should clue you into some of the folklore around it. Yes, its berries were believed to help monks keep their thoughts pure. Conversely, it has a long tradition in folk medicine for helping women with reproductive system issues. More recently it is valued simply as an ornamental, particularly in southern areas where lilacs don’t do well – it has a similar flower color. Vitex also has pretty good deer resistance and salt tolerance.
Blue Diddley® is a compact version of chaste tree. While traditional varieties can get large, even grow to be a small tree, Blue Diddley® maxes out at about 6′. In colder climates, Vitex agnus-castus is like Buddleia and behaves more like a perennial. It’s considered hardy to USDA Zone 5 as a dieback shrub, and will be a shrub in Zone 7 and warmer. Zone 6? Well, I guess it will depend on the winter. Check with your local extension service to see if it’s suitable for your area. Either way, it’s an interesting addition to a sunny bed or border. Just make sure the soil is well-drained.