There sure are a lot of trees that put on a showstopping bounty of blooms in spring, but there aren’t that many that can do it in summer. But chastetree (Vitex agnus-castus) can – and it’s one of the best.
The typical chastetree has a pointed inflorescence and marijuana-like leaves.
Photo Credit: Gerald L. Klingaman
‘Montrose Purple’ is an especially floriferous selection of chastetree, but the bloom spikes lack the typical pointed tip.
Photo Credit: Gerald L. Klingaman
chastetrees start out looking like a shrub, but they’ll grow 10-18 feet tall if you let them.
Photo Credit: Gerald L. Klingaman
Although you don’t find it too often, chastetree’s a widely adapted small tree or large shrub that reaches about 10-18 feet tall. It usually grows wider than tall, reaching out with spreading branches. A native to western Asia and southern Europe, it’s typically multi-trunked with distinctively palmate compound leaves. (In fact, the foliage looks a lot like marijuana leaves, and that’s why the plant’s sometimes called hemp tree.) If you crush the leaves, you’ll notice a very distinguishing aromatic smell.
While the tree’s a beauty to look at almost anytime of the year, it’s in the summer that it really shines. Blue to violet flower spikes appear in early to midsummer on the ends of new shoots. These spikes are branched, with the entire flower cluster reaching up to 1 foot long and wide! And the show continues on and off throughout summer. Once the flowers fade, the bloom spikes are covered with peppercorn-sized, round fruit.
Hardy from zones 6-9, chastetree is one of the few winter-hardy, woody members of the verbena family. It’s also a tough, drought-resistant plant. It needs full sun to bloom, but it’s not particular about soil type. Like most plants, the tree will grow larger in better soils and when some attention is paid to watering and fertilizing. Other than the possibility of root rot in heavy clay soils, chastetree isn’t bothered by insects or disease.
Summer-flowering selections like chastetrees make good additions to your shrub border, for screening or as lawn specimens. You can easily control the plant’s size with late-winter pruning. Because chastetrees bloom on new growth, hard pruning doesn’t disrupt flowering. When thinking of where to site your tree, remember it’s a favorite of butterflies, hummingbirds and bees (in fact, many beekeepers seek out chastetree as a summertime nectar source), so consider putting it where you can enjoy the wildlife – like near a patio or deck.
If your yard looks particularly “blah” in summer’s heat and humidity, think about bringing in the big blooms. With a sunny space to grow and a bit of tender, loving care, you’re sure to enjoy the bright, blue flowers of chastetree all summer long.
