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Scientific: Vitex trifolia
Common: Arabian lilac, simpleleaf chastetree, coastal vitex
Family: Verbenaceae (Lamiaceae)
Origin: Coastal regions of tropical east Africa as far east as French Polynesia.

Pronounciation: VI-tex AG-nus tri-FOL-ee-a

Hardiness zones:
Sunset 12-24
USDA 9-11

Landscape Use: Makes a nice large background shrub, large informal hedge or screen, smaller clipped hedge (high maintenance requirement), or a small multiple trunk shade tree for smaller residential and commercial landscapes; use for mesic or oasis landscape design themes, unique summer flowering accent tree or shrub.

Form & Character: Upright and asymmetrical, informal, soft, subtle, regal.

Growth Habit: Semi-deciduous, woody, broadleaf perennial large shrub or small tree, moderate growth to 15- to 20-feet tall with greater spread. Growth rate is faster in more tropical climates or when heavily irrigated.

Foliage/Texture: Leaves are opposite, variably ranging from simple and ovate to trifoliate (three lanceolate leaflets per leaf), sometimes abaxial leaf surfaces and petioles are purplish in color, sparse pubescence on young stems; medium texture.

Flowers & Fruits: Flowers with blue to violet corollas are born in panicles or clusters to 6-inches long, stamens are in two pairs. Flowers attract bees. Fruits are yellow-brown, small, in panicles, and are somewhat fleshy and contain 4 seeds.

Seasonal Color: Early summer flowers (generally May in Phoenix) that are not as showy as those of Vitex agnus-castus (lilac chaste tree). Fall color of senescing foliage of mature plants in Phoenix is wonderful some years depending on the advent of colder winter temperatures.

Temperature: Quite tolerant of desert heat, freeze intolerant when plants are young and tend to be more evergreen, shoots are damaged below 30oF, but will quickly recover. In contrast, older, established plants will transition to being deciduous during early winter.

Light: Full sun

Soil: Tolerant of alkaline soil.

Watering: Apply regular, deep. but infrequent water throughout the year.

Pruning: Arabian lilac can be trained many different ways (and it will need to be trained!) ranging from elevating the canopy base into a small multi-trunk tree to heading it back severely to any desired height. It's best to prune from December to early March, but can be lightly pruned most all year. Not unexpectably though the 'Horticultural clods of Phoenix' (aka 'Hort clods') will prune Arabian lilac the only way they know how to - frequent shearing.

Propagation: Softwood cutting, seed.

Disease and Pests: None

Additional comments: This is a wide spreading large shrub with an informal, asymmetrical growth habit! There are several cultivars including 'Purpurea' and 'Variegata'.

Medicinal notes: There are many locally indigenuous medicinal uses of this shrub. In fact, the entire genus Vitex is known for having medicinal uses.