There are two Vitex, Vitex negundo and Vitex agnus-castus. Vitex negundo has serrated leaves and was originally found in Southeast Africa, Madagascar and Southeast Asia. Vitex agnus castus is a smooth leaved species that is native to Southern Europe and Western Asia.
Both species are known as Chastetree. The foliage is fragrant and may repel mosquitoes. The form of Vitex is variable. In the south it can be trained as a large shrub of 8′ to 15′ high or as a small tree up to 25′ tall. Farther north in zones 5 and the upper portions of zone 6 it is grown as a tender perennial as a large shrub. In zones 5 and 6, Negundo is slightly hardier but even so, it will show winter injury in most years. USDA Zone Map In those areas, it is best to cut it back to the ground each year. Amazingly, it will grow back each year to 6′ to 8′ and bloom profusely, covered with beautiful lavender flowers.
Southern areas will find both species to be a relatively carefree plant. Few insects bother these plants. A few leaf spot fungi appear in wet years. Vitex is a tough plant that can survive the worst of growing conditions. Negundo is more tolerant of wet conditions but neither like wet feet. Agnus castus is at home on the rocky dry hillsides of the Mediterranean.
Vitex agnus-castus is showier with larger flowers than negundo. Varieties have been selected over the years for flower color, deep purple, red, lavender and white. Despite all this selection, Vitex is uncommon in the nursery trade. It needs a marketing team. Name recognition is a problem and confusion with another species. Buddleia resembles Vitex in flower form and flower color and has the appealing common name Butterfly Bush which helps it popularity. many people believe they have a Vitex when in fact they have a Butterfly Bush that does not attract bees at all. Vitex is more attractive to bees and other pollinating insects. it is also larger and far more spectacular in bloom. In parts of the south, Vitex is an important flowering tree for beekeepers. Where there are enough trees, it can make a significant summer honey flow.
The trees can be managed for a repeat bloom. It naturally blooms heavily in late June and July and then sporadically until frost. Once the heavy bloom fades, trimming the spent flower heads and seed heads will encourage another heavy bloom. One southern beekeeper mows his vitex every summer after the first bloom to get a heavy fall bloom.
Vitex was known as Chastetree in colonial times and was considered to have medicinal qualities. Since it responds well to being cut back, it is useful to gardeners for poles. Cutting back to the ground is called coppicing and cutting back above ground is called pollarding. These methods of pole production were common in Europe and were used here as well. Both methods will produce long straight whips that may be harvested every couple of years for many years. The poles may be used for bean poles or tomato stakes. Twiggy growth may be used for peas to climb.
Both Vitex are beautiful, useful, versatile pollinator friendly plants that should be found in more yards and gardens.