Meet Miss Agnes. She's "vital to chastity." That's how I remember her name...both the plant's botanical and common names. Students taking plant identification courses for landscape architecture find the botanical names particularly difficult to remember for tests. One way to remember is by word association (along with practice, practice, practice). I have internalized Vitex agnus-castus, but I will always greet this large shrub, small tree with "Hello Miss Agnes" (#plantnerd). She is quite the summer show-stopper, too, despite being chaste, which happens to be her common name: chaste tree. See cultural interests below.
Several references, including Sunset, note flower and leaf fragrance, but that has not been my experience. When crushed, the leaves do have a minor scent of, well, a crushed leaf, so I wonder if environmental influences like soil or time of day are influences. If anyone has another experience, please leave a comment. Regardless of fragrance, the intensely blue flower spikes can be show stoppers with the deep green leaves behind them.
Miss Agnus is not as common in the landscape as she could be, in part because finding the right place may be difficult. Planted too far away, people will not appreciate summer's bloom. Too close and its lower limbs might be in the way, and A. agnus-castus is not particularly interesting in winter. It seems the best locations might be where they can act as background during the summer, enhanced by flowers, but is not missed during winter's dormancy. I would not use it as a street tree since it is prone to being multi-trunk and low-limbed, but the wood is considered weak, which means limbs can easily break. I have not seen damaged branches on A. agnus-castus, so I am curious to know what conditions like wind or poor pruning practices might prompt such problems.
There once was a beautiful abandoned building at Depot Road and Sonoma Highway in Aqua Caliente. While the two-story building was gutted, the exterior thrived with a Cecile Brunner rose and at least one chaste tree. The combination of pink roses and blue spikes made for a romantic streetscape that is no more. What this location told me is that A. agnus-castus is a very drought tolerant species, thriving in dry, rocky soil. Given their ability to attract bees and butterflies, we should consider this shrub/tree a worthy landscape addition.
facts
Botanical Name: Vitex agnus-castus
Vitex: Traditional Latin name for the chaste tree
Agnus-castus: Greek, agnos, for this species; castus, meaning chaste
Common Name: Chaste tree
Family Name: Lamiaceae
Origin: Mediterranean region to Pakistan
design considerations
Positioning: Lawn, riparian (may lead to reseeding), patio, street, slope, forest edge
Garden Themes: Mediterranean, pollinator, informal/cottage, apothecary
Uses: Summer screen, container (not long-term), buffer, background, patio, mass, accent, essential oils
identifying characteristics
Type: Deciduous tree (multi-trunk or standard)
Form: Vase, round, spreading
Texture: Medium
Size: 15' wide x 15' tall
Outstanding Feature(s): Flowers, foliage
Bark: Dark gray and smooth (may become furrowed)
Leaf:
Type: Pinnately compound
Arrangement: Opposite
Shape: Palmate; lanceolate leaflets
Margin: Entire
Color: Blue-green above, lighter underneath
Surface: Smooth
Flower: Summer. Small, tubular, lavender flowers clustered in whorls along apical spikes. Possibly fragrant but would like to verify.
Fruit: Autumn into winter. Dark brown drupe.
cultural requirements, tolerances & problems
Sunset Zones: 4-24; H1, H2
USDA Zones: 7-9
Light: Full sun to part shade
WUCOLS SF Bay Area Hydro Zone: Low
Soil:
Texture: Sand, loam, clay, (rocky, well-drained)
Moisture Retention: May dry between watering
pH: Highly acidic to highly alkaline
Tolerances: Drought, heat; deer
Problems:
Branch Strength: Medium to weak
Insects:
Disease: Armillaria
cultural interests
Vitex has the common name "Chastetree" since Athenian women used the leaves in their beds to keep themselves chaste during the feasts of Ceres.
~ Gilman & Watson
Is it a coincidence that researches explored Vitex's capacity to help women with female reproductive disorders? Note to self to learn more about this Feast of Ceres, but wearing my empathy hat and the sometimes uncomfortable shoes of another gender (I've tried), I can imagine a time when having health challenges would prompt me to cover my bed with Vitex leaves to ward off any suitors. This is just my imagination running wild; please feel free to provide corrections in comments.
citations & attributions
Bayton, R. (2019). The Royal Horticultural Society's the Gardener's Botanical: An Encyclopedia of Latin Plant Names. London: Mitchell Beazley.
Gilman, E.F., Watson, D.G. (1994). Vitex agnus-castus; Chastetree. Forest Service Department of Agriculture. Retrieved on July 2, 2021, from http://hort.ufl.edu/database/documents/pdf/tree_fact_sheets/vitagna.pdf.
Missouri Botanical Garden. "Vitex agnus-castus." Accessed on July 5, 2021 from http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=g290.
Norris Brenzel, K. (Ed.). (2012). The New Sunset Western Garden Book. New York: Time Home Entertainment, Inc.
NC State Extension. "Vitex agnus-castus." North Carolina State University, Raleigh. Accessed on July 5, 2021 from https://plants.ces.ncsu.edu/plants/vitex-agnus-castus/.
Urban Forest Ecosystems Institute SelecTree. "Vitex agnus-castus Tree Record." 1995-2021. Cal Poly State University, San Luis Obispo. Accessed on July 5, 2021 from https://selectree.calpoly.edu/tree-detail/1464.
van Die, M. D., Burger, H. G., Teede, H. J., & Bone, K. M. (2013). Vitex agnus-castus extracts for female reproductive disorders: a systematic review of clinical trials. Planta medica, 79 (7), 562–575. https://doi.org/10.1055/s-0032-1327831.
Water Use Classification of Landscape Species. "WUCOLS IV Plant List." University of California, Division of Agriculture and Natural Resources, Davis. Accessed on June 28, 2021 from https://ucanr.edu/sites/WUCOLS/Download_WUCOLS_IV_List/.
Photos:
All photos by TELCS.