Chastetree (Vitex agnus-castus) is a deciduous (loses its leaves in the fall), multi-trunked shrub or small tree that is native to southern Europe and western Asia. It is an excellent selection for southern landscapes in USDA zones 7-9, but will have cold damage or be killed to the ground in USDA zones 6 and colder. The leaves, flowers, and seeds are aromatic with a spice-like scent similar to crushed sage.
Depending on the variety, the mature size of a chastetree can range from 3 to 20 feet tall and wide. The larger varieties are fast growers and may be grown as a large, vase-shaped shrub or trained into a small tree.
The oppositely arranged, grey-green leaves are palmately compound (hand shaped) with 5 to 7 lance-shaped leaflets. They are dark grey or blue-green on upper surface and greyish-green underneath with fine pubescent hairs. There is no significant fall leaf color.
The violet, blue, white, or pink 3 to 6 inch panicle (loosely branched flower cluster) flowers are produced on new growth. They begin to bloom in June and continue until September. Removing old blooms will encourage new growth with a repeat bloom in about six weeks. The bark is a greyish-tan that is smooth on a young tree but will become a fissured dark grey as the tree matures.
It prefers full sun and a loose, well-drained soil with adequate, but not wet soil moisture. After becoming established, it does well in a hot, dry setting (e.g. xeric or water-wise garden) and tolerates drought conditions.
Chastetree is resistant to damage by deer and is moderately salt tolerant. The fragrant flowers attract butterflies, bees, and other pollinating insects. In fact, it is often planted in areas to promote honey production.
Due to the chastetree’s interesting foliage and late summer flowers, it can be used in shrub borders, cottage or butterfly gardens, or as a small tree.
Chastetree is resistant to most insect pests and diseases. If planted in soil that is not well-drained or remains wet, it can succumb to root rot and dieback. Leaf spots can be a problem, especially if overhead irrigation is used. Several cultivars are available that have resistance to leaf spot.
Due to the possibility of reseeding, it can become invasive in some areas.
- ´Abbeville Blue´: This cultivar was selected in the early 1990’s and grows 6 feet tall and wide. It has 12 to 18 inch long, deep blue panicle flowers.
- ´Alba´: This large grower matures at a height of 10 to 15 feet and a width of 15 to 20 feet. The flowers are white.
- Blue Puffball™ (´PIIVAC-II´ PP26775): This compact cultivar grows 3 feet tall by 4 feet wide and is resistant to leaf spot. The flower panicles are deep blue. It was introduced by First Editions® in 2016.
- Blue Diddley® (´SMVACBS´ PPAF, CBRAF): This 2015 Proven Winners introduction is a compact grower. It has lavender-blue flowers on a 3 to 6 feet tall and wide shrub.
- Delta Blues™ (´PIIVAC-1’, PPAF): The blooms are dark purplish-blue, compact panicles. The foliage is more refined, and the plant will grow 8 to 10 feet tall and wide.
- ´Rosa Ann´: This variety will reach a height of 8 to 15 feet tall and 10 to 15 feet wide. The fragrant flower spikes are pink.
- ´Shoal Creek´: This is one of the more commonly available varieties and matures at 10 to 15 feet tall and 15 to 20 feet wide. The large, blue-violet flowers are 12-18 inches long. Foliage is resistant to leaf spot.