Updated: Nov 21, 2021
Ages ago...I am referring to my own ancient history...I was an outsider yet still involved with activities on Stanford's campus. My friends and I belonged to a club that was open to the community, and we took full advantage of the opportunity to connect with other students. "Other" truly meaning outsiders as we were. I first learned I could visit while attending Palo Alto High School; its adjacency to Stanford has been a constant influence on studious teens. I would continue visiting while attending Foothill Community College, and it was through that Stanford club I forged lasting friendships that are still true today. We'd dance into the night, crash a few institutional traditions (with Stanford students leading the way), hang out in a few dorm rooms talking past my curfew, or climb the dilapidated water tower attached to the old fire house. Good times!
When the fall semester begins at Stanford, I find myself walking the campus, exploring the landscape. It has changed over the years (that should be another post), but there is one tree I need to see each year, a kind of homage to a struggling rarity, Ceiba speciosa, or floss silk tree. I see both floss silk and silk floss written, so you decided which is best.
Its tropical appearance suggest high watering requirements when in actuality does just fine with drought. Maybe not to the severity of the last couple years, but here is what designers need to know. Once established, C. speciosa needs a deep watering only once a month during the dry season. As autumn approaches, watering should be reduced further which promotes greater blooming. This is not easy to accomplish if the tree is set on an irrigation line scheduled to water more regularly, so it may suffer from excesses. As it matures, the trunk can swell into a bottle shape, and as the form suggests, becomes a place to store yet more water. Of any tree, this one seems to be self-reliant in the right circumstances.
There are several online videos about the silk floss tree, but this one is filmed locally by Gary Gragg of Golden Gate Palms nursery.
Botanical Name: Ceibe speciosa
Ceibe: Referenced by San Marcos Growers, "The name Ceiba comes from a Spanish language interpretation of a Caribbean Taino word meaning a 'giant tree'."
Common Name: Floss silk tree
Family Name: Malvaceae
Origin: Brazil, Argentina, eastern Bolivia, Paraguay, Uruguay
Positioning: Background (safely away from contact)
Garden Themes: Tropical, open space, botanical, winter interest, autumn interest, Mediterranean, drought
Uses: Shade, specimen, accent, focal, silhouette, bonsai
Type: Deciduous tree
Form: Pyramidal when young becoming irregular, umbrella
Size: 50' tall by 40' wide
Outstanding Feature(s): Fall flower, trunk form and bark
Bark: Gray, green, orange, smooth unless significant thorns or prickly spines
Type: Pinnately compound
Shape: Palmate, leaflets elliptic (5-7 leaflets)
Color: Medium green, no fall color
Flower: Autumn. Blooming will overlap leaf drop. Showy, large, white to shades of pink, 5-petal funnel with prominent pistil.
Fruit: Autumn to Winter. Large capsules open to review "floss" seeds
cultural requirements, tolerances & problems
Sunset Zones: 12-24
USDA Zones: 10-11
Light: Full sun
WUCOLS SF Bay Area Hydro Zone: Low
Texture: Sand, loam
Moisture Retention: Well-drained. Watering should be deep, about once a month, then tapered at end of summer to promote greater flowering, according to Sunset (p. 241).
pH: Neutral to slightly alkaline
Tolerances: Drought, deer
Problems: Frost tender below 20° F. Fruit drop may be messy due to seed spread resembling cottony mass
Branch Strength: No observed at time of posting
Insects: Scale, spider mites
Disease: Leaf spot
'Los Angeles Beautiful': Deep pink blooms.
'Majestic Beauty': Spineless
There are several online videos about the silk floss tree, but this one is filmed locally.
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. "Ceiba speciosa." Department of Horticulture, College of Agricultural Sciences, Oregon State University, Corvalis. Accessed on October 22, 2021, from https://landscapeplants.oregonstate.edu/node/2137.
Gilman, E.F., Watson, D.G. (1993, November). "Chorisia speciosa: Floss-Silk Tree." University of Florida, Gainesville. Accessed on October 22, 2021, from https://hort.ifas.ufl.edu/database/documents/pdf/tree_fact_sheets/chospea.pdf.
Norris Brenzel, K. (Ed.). (2012). The New Sunset Western Garden Book. New York: Time Home Entertainment, Inc.
Plant Finder. "Chorisia speciosa." Missouri Botanical Garden, St. Louis. Accessed on October 22, 2021, from https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=277944.
Products. "Ceiba speciosa." San Marcos Growers, Santa Barbara. Accessed on October 22, 2021, from https://www.smgrowers.com/products/plants/plantdisplay.asp?plant_id=401.
SelecTree. UFEI. "Ceiba speciosa Tree Record." 1995-2021. Cal Poly State University, San Luis Obispo. Accessed on October 22, 2021, from https://selectree.calpoly.edu/tree-detail/351.
Water Use Classification of Landscape Species. "WUCOLS IV Plant List." University of California, Division of Agriculture and Natural Resources, Davis. Accessed on October 22, 2021.
Photos by TELCS