Common Name: Lilac Chastetree
Scientific Name: Vitex agnus-castus
Order: Lamiales
Family: Verbenaceae
Description Lilac chastetree is a deciduous, fast-growing, ornamental tree or shrub. It can grow to a height of 10 to 15 feet and can have a canopy width of 15 to 20 feet. The lanceolate leaves of this plant are opposite and palmately compound with 5 to 7 leaflets. Leaflets are 2 to 4 inches wide while the entire leaf is 4 to 8 inches long. The showy flowers of lilac chastetree are terminal spikes of white to violet and approximately 3 inches long. These flowers can bloom from June until September exclusively on new growth. The fruit are small, brown, inconspicuous capsules that persist through the winter. The fruit, however, does not attract wildlife.
Growth Habit Lilac chastetree is a fast-growing plant that can reach a canopy width of 20 feet. However, this, as well as floral development, is contingent on good soil moisture. It does well in almost any type of soil that is well drained. It also requires lots of sunlight for optimum growth and development.
Hardiness Zone(s) Lilac chastetree does well in USDA Zones 6-11. The ability of this plant to thrive well in Zone 6 indicates that it is cold hardy and can be enjoyed across much of the United States (excluding the north-central region and northern portion of the New England region). It does, however, prefer warm weather.
Culture This plant should be established in an area with full to partial sunlight. It tolerates sandy, loamy, clayey, acidic, and alkaline soils that are well-drained. It has a high drought tolerance and a moderate aerosol salt tolerance.
Diseases & Insects While insect pests are not of major concern in regards to the lilac chastetree, it can have some issues with aphids, scale, and white flies. The disease leaf spot can cause defoliation of this species. Root rot can also be a problem if the soils are kept too moist.
Landscape Value This plant works well when intermingled with other species to form a mixed shrubbery border, but also is great as an individual specimen. It can have multiple stems, or, if trained in a nursery, can have a single trunk. It is an especially great species for city landscaping because it will not grow tall enough to interfere with power lines or wide enough to obstruct the line-of-sight of drivers. It can be found in residential and commercial landscapes, such as around homes and businesses, and on road medians. Lilac chastetree is great for bird and butterfly gardens because hummingbirds and butterflies are attracted to its showy flowers. Bees are also attracted to the flowers. In fact, lilac chastetree is often planted in areas that are used for honey production.
References Gillman, E. F. and D. G. Watson. 2015. Vitex agnus-castus: Chastetree. University of Florida Institute of Food and Agricultural Sciences. Online.
This document was authored by Dr. Heidi Adams, School of Forestry, Louisiana Tech University, August 2015.