Updated: Aug 19, 2021
Summer is here, and I love chocolate, so let's dive right into a tree that does not receive too much attention. Meet the velvety chocolate descendent of Albizia julibrissin with its deep purple to burgundy leaflets that make the pink puffy flowers pop in summer. Its coloring was first noticed in 1990 when Dr. Masato Yokoi noticed a seedling singing, "I gotta be me!" with its unique coloring among its green brethren, as I loosely interpret from the U.S. Patent. Yes, plants are patented now, because horticulture science creates new plants all the time, and like musicians, their creators want to maintain rights of ownership. It has become a sensitive issue, because unscrupulous people will take plants home, propagate them, and resale them under different names in an attempt to make a buck. Champagne versus sparkling wine kind of thing...sort of.
Summer chocolate silk tree was patented by Hines Nursery, Inc., who holds patents on several species. For our purposes, summer chocolate does not reach the same size as its parent, but that might be debatable, since several websites describe its size anywhere from 20' to 40' tall. Their growth habit is similar, too, with horizontal branching causing beautiful layering, similar to larger Japanese maples. Minor pruning maintains an attractive silhouette.
For California designers, A. julibrissin 'Summer Chocolate' presents an opportunity to migrate away from the ubiquitous purple-leaf plums seen in too many commercial developments where they struggle under extended droughts or even insect invasions like the tussock moth. This purple-leafed silk tree is considerably more drought tolerant while still producing pink blooms. Of course, there is that size question; anything more than 20' and it will be larger than the purple-leaf plums. Their different overall form and texture should also be taken into consideration. Still, if purple leaves are desired as a contrast to green, this is a noteworthy option to withstand California's climate.
Botanical Name: Albizia julibrissin 'Summer Chocolate'
Albizia: Honoree, 18th century naturalist, Filippo degli Albizzi
Julibrissin: Persian, gul-ebruschin, for floss silk (referencing the delicate flower appearance)
Common Name: Summer chocolate silk tree; purple-leaf mimosa
Family Name: Sapindaceae
Origin: Iran to Japan
Positioning: Lawn, riparian (may lead to reseeding), patio, street, slope, forest edge
Garden Themes: Asian, Mediterranean, desert, pollinator, woodland
Uses: Shade tree, specimen, street, accent, foliage contrast
Type: Deciduous tree (multi-trunk or standard)
Form: Vase, umbrella, spreading (with horizontal branching)
Size: 20' wide x 20' tall (may become larger with age)
Outstanding Feature(s): Flowers, foliage, shade value
Bark: Dark gray and smooth
Type: Bi-pinnately compound
Shape: Elliptical to oval (leaflets are oblong, from 10-25 pinnules; 50-60 leaflets)
Color: Light green as new leaves unfurl turning deep purple above, bright burgundy underneath at maturity. Little to no fall color value.
Flower: Summer. Puffs of stamens, white to pink in apical clusters. Fragrant (close range)
Fruit: Autumn into winter or longer. Legume, deep brown
cultural requirements, tolerances & problems
Sunset Zones: 4-23
USDA Zones: 6-9
Light: Full sun to part shade
WUCOLS SF Bay Area Hydro Zone: Low
Texture: Sand, loam, clay, chalk
Moisture Retention: May dry between watering
pH: Highly acidic to highly alkaline
Tolerances: Drought, heat, poor soils, saline
Problems: Considered short-lived elsewhere
Branch Strength: Medium to weak
Insects: Borers, aphids
Disease: Armillaria, fusarium, root rot
citations & attributions
Bayton, R. (2019). The Royal Horticultural Society's the Gardener's Botanical: An Encyclopedia of Latin Plant Names. London: Mitchell Beazley.
Hines Nursery, Inc. "Albizia julibrissin tree named 'Summer Chocolate'." JUSTIA Patents. Accessed on July 2, 2021 from https://patents.justia.com/patent/PP13822.
Missouri Botanical Garden. "Albizia julibrissin 'Summer Chocolate'." Accessed on July 2, 2021 from https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=293062&isprofile=0&.
Norris Brenzel, K. (Ed.). (2012). The New Sunset Western Garden Book. New York: Time Home Entertainment, Inc.
NC State Extension. "Albizia julibrissin." North Carolina State University, Raleigh. Accessed on July 1, 2021 from https://plants.ces.ncsu.edu/plants/albizia-julibrissin/.
RHS. "Albizia julibrissin 'Summer Chocolate'." Royal Horticulture Society, London. Accessed on July 2, 2021 from https://www.rhs.org.uk/plants/258154/albizia-julibrissin-summer-chocolate-pbr/details.
Urban Forest Ecosystems Institute SelecTree. "Albizia julibrissin Tree Record." 1995-2021. Cal Poly State University, San Luis Obispo. Accessed on July 1, 2021 from https://selectree.calpoly.edu/tree-detail/147.
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/.
All photos by TELCS.