Clerodendrum trichotomum


This large shrub, small tree came my way from generous owners of a small resort in Guerneville. I would occasionally talk with them about the plants on property, and at the time I was unfamiliar with this species. Harlequin glorybower, as it is known, was reseeding in several places, so they gladly donated one to my education. Now about 8' tall and slow to achieve its ultimate height, it reseeded a couple times. Only one other has gained a foothold. I suspect seedlings do not like dryness or competition; there are already some well-established understory plants unwilling to give up space for another. This autumn, I will attempt to purposefully propagate a few; the current plants are in the way of some garden remodeling and may not be saved. Relocation is our first choice, but starting new ones are back up plants just in case.


C. trichotomum has a stately form, symmetrical, low branching, with vase-shaped branch scaffolding, defies other observations classifying its form as irregular, suckering, and an unkempt appearance. We must be lucky! Online searches has shown photos of specimens trained as standards for street trees (photo below), which seems odd given how small they are at maturity.


The flower fragrance is delightful, somewhere between jasmine and stephanotis. Individual flowers are showy, but their blooming seems sparing amidst the clusters. In other words, there are clusters and photos online showing many blooms at once, but ours has a bloom here and there despite bud clusters looking ready to burst. This may be a ploy to conserve energy at this driest time of year (a guess on my part). An observation that should be cross referenced. Its leaves offer something else surprisingly fragrant. When crushed, they briefly smell like peanut butter. I could not believe when reading about it, but I can attest to this distinct scent.


It has yet another showy benefit, hence the harlequin reference. After flowering, the calyx will turn bright red and reveal in its center a deep blue fruit. As a cluster, the pattern does remind me of the diamond pattern associated with harlequins. Best suited in an intimate garden, perhaps a courtyard, where the subtle fragrance and beauty can be enjoyed.



facts

Botanical Name: Clerodendrum trichotomum

Clerodendrum: Greek, kleros for chance; dendron for tree (unclear reference meaning)

Trichotomum: Three-branched (unclear reference meaning)

Common Name: Harlequin glorybower

Family Name: Lamiaceae


Origin: Japan, eastern China


design considerations


Positioning: Background, lawn, forest edge, planter

Garden Themes: Sensory, woodland, courtyard/patio, urban

Uses: Border, specimen, informal hedge, mass, understory


identifying characteristics


Type: Deciduous tree

Form: Irregular, open, round (natural form has low branching)

Texture: Coarse

Size: 20' tall and wide (multi-); may become taller as standard


Outstanding Feature(s): Flower, fragrance, fruit clusters (decorative)


Bark: Green-brown and smooth in youth turning warm gray and lightly fissured or scaly with age.

Leaf:

  • Type: Simple

  • Arrangement: Opposite

  • Shape: Ovate to deltoid

  • Margin: Entire to slightly crenate

  • Color: Medium green

  • Surface: Slight pubescence, more prominent on underside along veins

Flower: Summer. Showy cyme of tubular flowers opening star-shape. White, lightly fragrant.

Fruit: Autumn. Star-shape calyx behind deep blue drupe, showy in clusters


cultural requirements, tolerances & problems


Sunset Zones: 15-17, 20-24

USDA Zones: 7-9


Light: Sun; prefers partial shade in the afternoon

WUCOLS SF Bay Area Hydro Zone: Moderate

Soil:

  • Texture: Loam, well-composted

  • Moisture Retention: Well-drained

  • pH: Acidic to lightly alkaline

Tolerances: Deer

Problems:

  • Branch Strength: Medium

  • Insects: None recorded at time of posting.

  • Disease: None recorded at time of posting.


citations & attributions


Bayton, R. (2019). The Royal Horticultural Society's the Gardener's Botanical: An Encyclopedia of Latin Plant Names. London: Mitchell Beazley.


Breen, P., Landscape Plants. "Clerodendrum trichotomum." Oregon State University, Corvalis. Accessed on August 31, 2021, from https://landscapeplants.oregonstate.edu/plants/clerodendrum-trichotomum.

Extension Gardener. "Clerodendrum trichotomum." North Carolina State University, Raleigh. Accessed on August 31, 2021, from https://plants.ces.ncsu.edu/plants/clerodendrum-trichotomum/.


Norris Brenzel, K. (Ed.). (2012). The New Sunset Western Garden Book. New York: Time Home Entertainment, Inc.


Plant Finder. "Clerodendrum trichotomum." Missouri Botanical Garden, St. Louis. Accessed on August 31, 2021, from http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=287499.


SelecTree. UFEI. "Clerodendrum trichotomum Tree Record." 1995-2021. Cal Poly State University, San Luis Obispo. Accessed on August 31, 2021, from https://selectree.calpoly.edu/tree-detail/371.


Water Use Classification of Landscape Species. "WUCOLS IV Plant List." University of California, Division of Agriculture and Natural Resources, Davis. Accessed on August 31, 2021, from https://ucanr.edu/sites/WUCOLS/Download_WUCOLS_IV_List/.


Photos:



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