Admittedly, I only discovered this tree when developing our plant list for student studies, so in this situation, I am the student as well. Cal Poly's Urban Forest Ecosystems Institutes illustrates examples growing in Berkeley and Santa Barbara, which supports Sunset's comment, "Blooms best in coastal conditions" (p.397). Commonly called primrose tree, it tolerates a number of conditions we have in California: diverse soils, ocean winds and salt spray, intense heat, and bounces back from frosts. So why is this tree not more readily seen in our ornamental landscapes further inland?
One problem, also noted from the above references, may clarify its other common name, the cow itch tree. After blooming, the brown seed capsules are coated with fine hairs acting as an irritant to skin. I am assuming this is a problem only if cows rub up against them, but I am also thinking the hairs could irritate people. San Marcos growers, another informative reference, offers this observation:
"A beautiful and adaptable tree but the possible interaction with the irritating seed fibers (akin to fiberglass) should be taken into account when determining placement in the garden."
So, don't wallow in its branches! How much of an irritant is still in question, since Sunset also mentions the seed capsules are popular among florists. If anyone out there has had some experience with this tree, I would love to see your comments.
Several references discuss its use in coastal areas, an appropriate location when considering yet another common name alluding to its origin, Norfolk Island hibiscus. I am imagining a garden with this tree interspersed with another island native, Norfolk Island pine. Coastal areas, certainly, even in San Francisco, but its apparent tolerance of "intense heat" suggests L. patersonii could be fine inland as well, providing the region is not susceptible to frosts below twenty-five degrees Fahrenheit. Its overall size lends itself to street tree locations but perhaps not well suited to canopy over patios and outdoor dining tables. So, what do you think? Should this tree be more integrated into California's landscapes?
Botanical Name: Lagunaria patersonii
Lagunaria: Honoree, botanist and physician Andrés de Laguna
Patersonii: Honoree, soldier and botanist William Paterson
Common Name: Norfolk Island hibiscus; primrose tree; cow itch tree
Family Name: Malvaceae
Origin: South Pacific, Australia
Positioning: Background, streets, parks
Garden Themes: Tropical, coastal
Uses: Street tree, screen, windbreak if as large hedge, specimen, accent
Type: Evergreen tree
Form: Upright when young, spreading with age
Size: 30' tall and wide
Outstanding Feature(s): Flower
Bark: Light and dark gray, rough with fissures
Color: Drab blue-green above, gray-green underneath
Flower: Summer. Showy but small hibiscus form in shades of pink
Fruit: Autumn. Fuzzy brown capsule may be an irritant
cultural requirements, tolerances & problems
Sunset Zones: 13, 15-24; H1, H2
USDA Zones: 9-11
WUCOLS SF Bay Area Hydro Zone: Low
Texture: Sand, loam, clay
Moisture Retention: Well-drained
pH: Very acidic to very alkaline
Tolerances: Salt spray, heat, deer
Branch Strength: Medium
Insects: None recorded at time of posting.
Disease: Phytophthora, 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.
Norris Brenzel, K. (Ed.). (2012). The New Sunset Western Garden Book. New York: Time Home Entertainment, Inc.
Plant Finder. "Lagunaria patersonii." Missouri Botanical Garden, St. Louis. Accessed on August 31, 2021, from http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=277946&isprofile=0&pt=2.
SelecTree. UFEI. "Lagunaria patersonii Tree Record." 1995-2021. Cal Poly State University, San Luis Obispo. Accessed on August 31, 2021, from https://selectree.calpoly.edu/tree-detail/799.
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/.
Flower detail purchased from Shutterstock