The chaste tree is a heat- and drought-tolerant plant with attractive foliage and lavender flower spikes that lure bees and butterflies to your garden. The individual flowers are tiny and lipped, ranging from purple or violet to pale lavender. Attaining a lovely upright shape with wispy branches covered in feathery leaves, a chaste tree makes a great specimen shrub or small tree in the garden border or large patio container.
At least three species of chaste tree are known in gardens, all belonging to the botanical group or genus Vitex, part of the vervain family, Verbenaceae. The three species of chaste tree are: Vitex agnus-castus, Vitex negundo and Vitex trifoliata.
Chaste tree species are native to the warm regions of the Old World. Vitex agnus-castus grows naturally from the Mediterranean Sea eastward to central Asia. Vitex negundo hails from southeastern Africa to across southern and southeastern Asia, and Vitex trifolia is native to southeastern Asia and Melanesia.
All three chaste trees have attractive foliage that has a feathery texture on the branches. If the leaves are crushed, a pleasant aroma is released. The leaves are light green to pale silvery green in color and are compound, with three to seven narrow, tapering leaflets. Large plants have papery, grayish-brown bark. The crowning glory of these plants is the purple or violet to lavender flowers that occur in fingerlike clusters, called panicles, at tips of branches. They are sweetly fragrant and attract bees and butterflies.
Tolerant of hot temperatures and dry soil conditions, all chaste trees grow well in any soil that is well-draining, those that drain within five minutes after a rain and never flood. A slightly moist soil across the growing season ensures the lushest display of foliage on a nicely shaped plant. Full sun exposures, direct sunlight for over eight hours daily, guarantees abundant flowering. The plants do well with only four to eight hours of sun each day, but stems are longer, leaves fewer and less prolific flowering occurs.
Chaste trees differ in their hardiness to winter cold. Vitex agnus-castus and Vitex negundo are best in USDA Plant Hardiness Zones 6 through 9; Vitex trifolia is not tolerant of frosts and thus only good in Zones 10 and higher.
Fast growing when temperatures are warm, prune the tree back in late winter and again in the middle of summer after the first flowering display to encourage new growth and more compact, rounded shrubs. Removing only lowermost branches from the trunk creates a tree-like silhouette. Deadhead, or cut off spent flowers, to promote new growth and a repeat flowering one to three months later.