Five reasons you should plant a Vitex
If you garden in zone 6 or warmer and your garden doesn't include Vitex agnus-castus—commonly known as chaste tree, or Texas lilac, or just vitex—I'm here to make the case for adding one to your shopping list this season.
Reason No. 1: Hello, look at those spectacular purple blooms (here on the cultivar "Shoal Creek"). They practically cover this large shrub/small tree. (I have seen vitex close to 20 feet high at the Atlanta Botanical Garden, but they are easy to keep smaller.) And, if you deadhead after blooming, you can probably get three flushes of bloom a season. For me, in Florida, that means blooms from May to almost November.
Reason No. 2: The blooms aren't just pretty, they are magnets for all manner of winged pollinators. Bees and butterflies (like the Pieris rapae in this photo) flock to this plant.
Reason No. 3: It can serve as a beautiful specimen plant, but also plays well with others in a mixed perennial-shrub border. I prune mine to a large multi-stemmed form, as shown here.
Reason No. 4: It will cause your friends to wonder what you're up to, because the leaves bear more than a passing resemblance to cannabis. (If salt-tolerance is an issue for you, the foliage is moderately so. If we have a big coastal storm, it takes something of a beating and I try to give the foliage a good rinse afterward.)
Reason No. 5: You really did want another look at those flowers, didn't you? Vitex produces them while being amazingly heat- and drought-tolerant. Those qualities, and its generally resistance to pests, caused Texas A&M to name it a "Texas Superstar." Here's one caveat: In zone 6, you may want to plant this in a protected spot, say against a wall, where it can get some reflective heat in the coldest parts of winter. It may die back to the ground during the winter in the northern parts of its range, but should come back from the roots and can easily grow 5 feet in a season.