Scientific:
Vitex agnus-castus
Common: lilac chaste tree, chasteberry, Monk's pepper tree, Abraham's balm
Family: Verbenaceae
Origin: Southern Europe, but used as a landscape element across the southern United States. It has naturalized in the southeastern United States and seed will germinate readily in irrigated Phoenix landscapes.
Pronounciation: VI-tex AG-nus CAS-tus
Hardiness zones:
Sunset 4-24
USDA 6-11
Landscape Use: Lilac chaste tree makes a nice large background shrub, to small multiple trunk shade tree for residential and commercial landscapes; use for mesic or oasis landscape design themes, unique summer flowing accent tree or shrub.
Form & Character: Winter deciduous habit makes for a distinct bimodal character (ugly during winter, beautiful during summer), upright, arching and spreading, rounded when mature, regal when flowering.
Growth Habit: Deciduous, woody, broadleaf perennial large shrub to small tree, moderate growth rate to 20-feet tall with equal spread. Growth rate and floral display related to irrigation and moisture availability.
Foliage/Texture: Classic palmately compound leaf, 5 to 7 lanceolate entire leaflets (not dentate like Cannabis sp.) to 6-inches long, dull green, aromatic, slightly pubescent when young; medium texture in summer.
Flowers & Fruits: Terminal plumes/spikes of white, pink to violet blue (most common color) flower plumes to 3-inches long, flowers attract bees; fruits are aromatic, small brown seed capsules on stalks, unsightly and persistent through the winter months.
Seasonal Color: Lilac chaste tree produces copious and intense plumes of blue flowers in early summer (that would be late May to June in Phoenix). During late winter, lilac chaste tree leaves turn a golden yellow color, though the intensity of fall color varies from year-to-year in Phoenix depending on the late fall and early winter temperature profile.
Temperature: Lilac chaste tree needs summer heat for best flowering, and because of this it's no surprise that it flowers like crazy in Phoenix during May and June.
Light: Full sun
Soil: Tolerant, even of soil alkalinity.
Watering: Apply regular, deep. but infrequent water from April to October. Little to no supplemental water is needed during the rest of the year. Like bougainvillea, more water = faster growth, but fewer flowers.
Pruning: Lilac chaste tree may be trained in many different ways ranging from elevating the canopy base into a small tree to heading it back severely to any desired height. Best to prune while dormant from December to early March.
Propagation: Seed
Disease and Pests: Aphids, scale, and white flies
Additional comments: In Phoenix, lilac chaste tree is a great large shrub or small multiple trunk tree for an early summer (May-June) floral display. Some clients may not like this plant because it is deciduous (sticks and seeds) during winter!.
There are many outstanding cultivars including:
Biomedical note: Vitex has a long history of medicinal value including rerecent discoveries of antioxidant and antidiabetic bioactive compounds.
