By Ellen Reardon and Carl Price. First published in Let's Talk Plants! August 2008, No. 167.
In a previous essay* we referred to a meeting at Penn State University at which we listened in awe as John Ritter of North Carolina State University discussed the origin, and decline, of women’s “take-charge” roles in managing their bodies prior to the 1400’s. He specifically cited the chaste tree, Vitex agnus-castus, from both a botanical and medical perspective. Throughout much of history, many European women had “known” how to use the extracts of the chaste tree to enhance or decrease fertility; that is, until the 15th century. As a small group of us discussed the rationale for this sudden termination of the dispensation of knowledge, Dr. Ritter supplied us with the surprising-but-true history — the rise of medical schools: Women who knew these facts had to be witches, therefore they were burned at the stake! Extracts of Vitex agnus-castus act by inducing progesterone so that ovulation may be enhanced or repressed, and physicians certainly couldn’t allow ignorant peasant women to undercut the medical profession!
The chaste tree is endemic to the Mediterranean regions, New Zealand, and Kenya, so it is also a natural for Southern California. It is heat loving, drought and deer tolerant, and even resistant to salt drift. Unfortunately, it is susceptible to mushroom root rot and nematodes. Formerly classified as in the Verbena family, it has recently been transferred to the Lamiaceae (mint) family. There are about 250 species of the genus Vitex, and V. agnus-castus can be grown as a small deciduous tree or a large shrub, growing 10–20 feet (3–6 m) tall. A landscape specimen carried by the California Flora nursery bears spikes of lavender-blue flowers in the summer.
The leaves of V. agnus-castus are 3–4 inches (7.6–10 cm) in diameter with 5 to 7 fingerlike leaflets, grey-green to dark green, with an aroma similar to that of sage. The leaves bear a strong resemblance to Cannabis (!) species, inspiring another common name: hemp tree. While flowering**, it is often mistaken for the butterfly bush (Buddleia spp.) because of the similarity of their blooms.
If pruning is necessary, do it in winter, since the blooms form on new wood. It can easily be propagated by seed or by cuttings, which root easily in warm weather. It is hardy in USDA zones 6–10, but may need additional protection against the cold in zone 6. We seldom have that problem here.
*Plants That Heal, September 2007
**The original photograph accompanying this article of flowers of the chaste tree, Vitex agnus-castus, is by Jack Scheper, Floridata.com., and can be downloaded from www.floridata.com/ref/v/vitex_a.cfm.
Members Ellen Reardon and Carl Price are retired from Rutgers University, where they conducted research on the molecular biology of plastids and served as editors of journals in their field.