Considering how few shrubs or trees bloom in lilac, blue, or purple, it’s surprising more gardeners haven’t discovered chaste tree (Vitex agnus-castus). Considering how many want pest-free, deer-resistant plants that bloom for weeks, it’s amazing this tree is almost uncommon in our state. Fast-paced growth soon forms several trunks topped by a canopy that reaches out in every direction. Leaves and flowers have distinct, if subtle, aromas, attracting bees and hummingbirds to the tubular flowers.
Chaste tree can hold its own amid prize-winning daylilies or welcome visitors at streetside, even stop traffic with its beauty. Upright branches hold their flowers at attention as if to salute the hot weather that brings on the blooms. Like the Beefeaters at Buckingham Palace, they stare straight ahead and never wilt in the humidity. But unlike the red uniformed palace guards, chaste tree’s colors are cool, and so is their impact on the garden. When spring warms the soil, chaste tree puts on its leaves, and the new, light green growth darkens quickly as they expand. As summer heats up, dozens of showy flower clusters adorn chaste tree; it truly buzzes with life.
At its best, chaste tree is an asset in gardens large and small. Ignored for a few seasons in any garden, it becomes unruly, a twiggy, thickety mess and sparse flowers. If many stems continually sprout from the ground, select three of them, remove the rest, and use a less-nitrogen rich fertilizer such as one made for flowering trees. A late winter or early spring pruning to remove dead twigs and shape the canopy yields big results in two ways. Keeping the twigs cut off reveals the gnarly trunks and, since chaste tree blooms on the current season’s growth, tip pruning brings on more flowers. Each time they fade, deadheading to remove spent blossoms will spur another round, especially if you follow the grooming with fertilizer.
Vitex seedlings can vary widely; just because Mama is dark blue doesn’t mean the seedling you find sprouting next to her will be. Named varieties recommended across the South include ‘Abbeville Blue’ with dark blue spikes, ‘Rosea’ (dusty pink), ‘Shoal Creek’, noted for huge violet spikes, and ‘Fletcher Pink’ a dramatic light purple-pink with especially fast growth. Chaste tree can grow anywhere in our state, and is both drought- and salt-tolerant, but will be a larger plant nearer the Gulf Coast.
Here’s a capsule of facts about chaste trees:
Common Name: Chaste Tree
Botanical Name: Vitex agnus-castus
Varieties to Look For: ‘Abbeville Blue’, ‘Rosea’, ‘Alba’
Color: blue, pink, white
Blooming Period: summer into fall
Type: deciduous large shrub or small tree
Size: 10’-15’ and as wide
When to Plant: fall to spring
How to Plant: 5’-8’ apart
Watering: drought tolerant once established
When to Prune: late winter
When to Fertilize: compost in early spring and flowering tree formula in late spring
*some of this article was first included in MS Gardener, 2005.