Right now in Eastern North Carolina landscapes, a lovely and under used small, deciduous, ornamental tree or shrub, Vitex agnus-castus, chastetree, vitex, or lilac chastetree, is blooming. When I returned from a meeting about a week ago mine at home was in full bloom. Ours in the Certified Plant Professional Collection at the Pitt County Arboretum is in full bloom this week also. Chastetree has opposite palmately compound leaves with five to seven leaflets. Each leaflet is widest at the middle, longer than wide, gray-green on the upper side and light gray beneath due to a number of fine hairs.
The flowers are arranged in clusters along a spike. Flower color of the species is lilac or pale violet and they occur from June through September. Most blooms have occurred in June and July in the past in the Pitt County Arboretum with some sporadically appearing through September. Because of the shape and color of flowers people often confuse this plant with butterfly bush. Since the blooms occur on new growth, old blooms could be pruned off as they fade on small plants to promote new growth and new blooms later in the season.
Chastetree can grow up to 25 feet tall and wide. Nurseries usually train them as multi-trunk small trees or large shrubs. Two to three feet of growth a year is common.
As plants get older the gray bark becomes blocky in appearance similar to that of dogwoods.
A number of cultivars are available to choose from if the straight species is not to your liking. Here are the ones listed in Michael Dirr’s Manual of Woody Landscape Plants: ‘Abbeville Blue’ has deep blue flowers, ‘Alba’ has white flowers, ‘Blushing Spires’ has soft pink flowers, ‘Fletcher Pink’ has lavender-pink flowers, ‘Lilac Queen’ has lavender flowers, ‘Mississippi Blues’ is a smaller plant growing to 12 feet with deep blue flowers, ‘Montrose Purple’ has violet flowers, ‘Rosea’ has pink flowers, ‘Salias Pink’ has light pink flowers, ‘Shoal Creek’ has blue-violet flowers, ‘Silver Spire’ has white flowers, ‘Snow Spire’ has white flowers, and ‘Woodlanders White’ is of course white.
Plants prefer full sun, hot weather and well-drained soil. If you would like to see a chastetree we have one in the Certified Plant Professional Collection of the Pitt County Arboretum located in front of the Agricultural Center and one in the mixed border behind the building. Many nurseries grow this plant in containers. Plant it as you would any other tree. Soil testing should be done if you have never done so or if it has been over three years since the last one. Prepare a planting hole at least twice as wide as the root ball and no deeper than the root ball. Use a knife or shovel to make several vertical cuts around the outside of the root ball to cause any circling roots to branch or use your hands to loosen roots around the edge. Soil amendments are not needed if digging a single hole and planting. Backfilling with the soil that came out of the hole is best, lightly tamping every few inches to remove air pockets. Water after the hole is two thirds full to further settle air pockets, backfill with remaining soil and water in again. Make sure not to cover the root system with soil or mound soil against the stem. Mulching with the product of your choice to a depth of two to four inches and at least to the edge of the canopy. Do not place mulch directly against the stem. To date there are no major disease or insect problems associated with this plant.
If you are interested in growing your own chastetree, softwood cuttings taken from new growth are easy to root. Take cuttings about 4 to 6 inches long from new growth, remove flowers and lower leaves, dip cutting in rooting hormone, and stick into sand or other well drained planting mix and water. Place the container the cuttings are stuck into in a clear plastic bag to produce a humid environment. Keep cuttings misted in a lightly shaded area until roots develop and then water less frequently.
Vitex is truly a tough, small, ornamental tree with many different uses. Train it as a small multi-stemmed or single stemmed tree, a large shrub, or you can even plant it in the perennial border and cut it back to the ground every year. By the way, vitex is very drought tolerant. Yet another reason to give one a home in your yard. Extension Agents and the NC Nursery and Landscape Association have selected the cultivar Shoal Creek as a Showstopper Plant for 2013. More information on this and other showstopper plants can be found at http://www.tarheelgardening.com/wordpress/2013/03/.
If you have gardening questions give the Master Gardener Extension Volunteers a call at the N.C. Cooperative Extension office in Pitt County at 902-1705 or email questions to firstname.lastname@example.org. More gardening information can be found at https://pitt.ces.ncsu.edu.