Tea-oil camellia blooming in the Arboretum in November (Photo by Niall Dunne)
BY CORINNE KENNEDY
Camellia oleifera is a cold-hardy species of camellia that bears lovely, fragrant, white flowers in autumn. It’s relatively rare in American gardens, but the Seattle Japanese Garden is fortunate to have a large specimen growing next to the Garden’s original East Gate. In 1962, the Washington Park Arboretum obtained one plant from the U.S. Plant Introduction Station in Glenn Dale, Maryland, propagated there from seeds originally received from Nanjing, China. It was planted in the north end of the Japanese Garden in 1970 and relocated to its current location a decade or two later. (There’s also a specimen in the main Tea Family Collection in the Arboretum; see “Tea-Oil Camellia in the Arboretum” below.)
Camellia oleifera is a broadleaf evergreen shrub or small tree noteworthy as the main camellia species cultivated for its oil-bearing seeds. In fact, the species name oleifera means “oil-bearing.” Common names include oil-seed camellia, tea-oil camellia and tea-oil tree. (The genus Camellia, in the family Theaceae, includes more than 275 species and was named in honor of Georg Joseph Camel, a 17th century German Jesuit missionary, pharmacist and naturalist who served in the Philippines.)
A Source of Valuable Seed Oil
Oil-seed camellia is native to China, Laos, Myanmar and Vietnam. Wild populations grow on streambanks and in forests and thickets at elevations of about 1650 to 4000 feet. Oil-seed camellia is the hardiest species in its genus, with a native range extending farther north than that of any other camellia. In China, the plant has been widely cultivated for more than 2300 years for the edible oil pressed from its seeds. Known as tea seed oil or camellia oil, it is used primarily in China and other Asian countries as a high-temperature cooking oil. Though other camellia species are also used, C. oleifera is by far the most important source of this valuable oil.
The fruit and seed.(Photo courtesy www.soapkitchen.co.uk)
The seeds are pressed after the mature seed pods crack open, and the oil is not only used for cooking but also in cosmetics and traditional medicine. Tea seed oil is lightweight, mild tasting, delicately scented, and high in antioxidants and beneficial fats. Camellia seed cake, a byproduct of oil production, is also used in cooking and cosmetics, and as feed for livestock. Other by-products are widely used in the chemical, papermaking, textile and other industries, and oil seed camellia is considered to have great economic promise, with new uses yet to be discovered.
Attractive Form, Leaves, Bark and Flowers
Camellia oleifera is a large, dense, multi-trunked evergreen shrub or small tree with an upright, rounded habit. It grows up to 25 feet tall in the wild, but cultivated plants mature at about 20 feet tall by 15 feet wide. Their trunks and branches are slender, with smooth, cinnamon-colored bark.
Oil-seed camellia’s glossy, leathery, deep-green leaves are simple, toothed, and about three inches long. Held alternately on the stems, they are oval in shape and tapered at both ends. Like the leaves of the tea plant, Camellia sinensis, the leaves of oil-seed camellia can also be used to brew tea.
Flowers are single, fragrant, and typically white or white with tinges of pink on the petal edges. Sometimes, they can be entirely pink. Opening in fall and early winter, the blooms are two-to-three inches wide, with five-to-seven slightly twisted petals and bright-yellow stamens. The fruits that follow are rounded, woody capsules about one inch wide. Botanically, Camellia oleifera is very similar to Camellia sasanqua and has often been incorrectly identified as the latter. (In fact, some authorities maintain that C. oleifera is the Chinese form of C. sasanqua.)
Camellia oleifera grows best in moist, acidic, organically rich soils, in part shade. With suffi-cient water and protection from reflected heat, it tolerates full sun here in the Pacific Northwest. It is hardy to USDA Zone 7 (minimum temperature 0 degrees Fahrenheit), but established plants may tolerate slightly colder tempera-tures for short periods. Like other camellias, it is susceptible to viruses and some fungal diseases, including flower blight, cankers and root rot. Stressed plants may be attacked by aphids, scales and spider mites.
Camellia oleifera in bloom in the Seattle Japanese Garden. (Photo courtesy Aleks Monk)
Use in Breeding Cold-Hardy Hybrids
In the late 20th century, the U.S. National Arboretum in Washington, D.C., developed an important program breeding cold-hardy camellia hybrids from Camellia oleifera stock. An oil-seed camellia specimen there was the only camellia that survived an extremely cold winter in the late 1970s. Renowned hybridizer Dr. William Ackerman noticed that crosses of C. sasanqua and C. oleifera derived from this plant were better garden performers than either parent or C. oleifera alone—and were hardy enough to do well in the East Coast states.
The aim of his breeding program was to produce heavy-blooming camellias of greater hardiness than were currently available—culti-vars that flowered in autumn, before the start of harsh winter weather. He made interspecific crosses between C. oleifera and selections of three other species (C. sasanqua, C. hiemalis and C. vernalis). The resulting hybrids, released in 1991, showed little or no winter injury in USDA Zone 6 (minimum temperature -10 degrees Fahrenheit). In leaf and flower, most resembled C. sasanqua cultivars, as if they were newly discovered cold-hardy sasanquas.
Ackerman’s Winter Series hybrids comprise these early releases, as well as plants developed in later years. They include ‘Polar Ice’, ‘Snow Flurry’, ‘Winter’s Charm’, ‘Winter’s Hope’, ‘Winter’s Interlude’, ‘Winter’s Joy’, ‘Winter’s Rose’, ‘Winter’s Snowman’ and ‘Winter’s Star’. With their glossy, bright-green leaves, attractive white-or-pink autumn flowers, and reliable cold hardiness, they are excellent garden plants, suitable for both the greater Seattle area and colder regions of the Pacific Northwest. ‘Winter’s Joy’ and ‘Winter’s Snowman’ are two cultivars that are readily available at retail nurseries here.
As a former woody plant buyer for retail nurseries, I find Camellia oleifera fascinating—for both its usefulness in breeding camellia cultivars and for its centuries-long importance as a source of oil. Ultimately, though, I love the elegant simplicity of its single, fragrant flowers and the beauty they bring to this season of transformations.
Camellia oleifera blooming in the Japanese Garden in November. (Photo by Corinne Kennedy)
Tea-Oil Camellia in the Arboretum
The larger Washington Park Arboretum plant collection contains an even more venerable specimen of tea-oil camellia. In March 1941, a single plant (accession #694-41)—16 inches tall and originally identified as Camellia cuspidata—was received from renowned nurseryman Koichiro Wada, owner of Hakoneya Nurseries, Numazushi, Japan. It was part of a very large shipment of mostly C. sasanqua varieties.
In November 1949, Arboretum Director Brian O. Mulligan examined the plant in bloom and identified it as Camellia oleifera. He also contacted the Arnold Arboretum, which confirmed his judgment. But there was another taxonomic twist in the tale. In 1953, British botanist John Robert Sealy, an expert on the genus Camellia, identified the Arboretum’s plant as an unnamed variant of Camellia oleifera. As a result, the Arboretum’s paper accession card was updated to list it as “Camellia oleifera variant.”
The very small original plant was probably grown on in the old lath house portion of the Arboretum nursery for several years before being planted. (In the 1940s, small plants were sometimes trampled by dogs or people—and occasionally stolen.) The planting date was not recorded, but it was most likely planted before November 1949—a flowering period noted on its accession card, without any reference to a nursery location. (Unfortunately, planting records weren’t detailed and uniform until 1949, when they were systematized under the leadership of Director Mulligan. Records do indicate that many camellia plantings were made in the early-to-mid 1940s.)
The Wada accession was planted in “bed C” of the Camellia Collection (Map Grid 11-5E), next to a western red cedar and near a grouping of C. sinensis (2025-40A, B, C, and D). (It’s on the southwest perimeter of the circular glade area of the collection, which features a bench and a large specimen of Magnolia × veitchii.) Decades later, the area had become deeply shaded by the cedar, which had grown very large. Fortunately, the Camellia oleifera variant has responded well to canopy-thinning work performed in 2015–16 to let in more light.
Notations on the accession card include a reference to its mid-December flowering in 1963 and a 1992 description of the flower as “small, single white, fragrant.” In a recent email, UW Botanic Gardens Curator Ray Larson commented that “There have been other C. oleifera plantings in the Arboretum in the past, but it has never been common…. It is a charming species that I would like to have more examples of.”
Adapted from a post that first appeared on the Seattle Japanese Garden blog.
Corinne Kennedy is a Garden Guide, a frequent contributor to the Seattle Japanese Garden blog, and a retired garden designer. She is also a member of the “Bulletin” Editorial Board.
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This article is reprinted from the fall 2024 issue of the Arboretum Bulletin, our quarterly botanical and horticultural magazine. Published since 1937, the Bulletin is a benefit of Arboretum Foundation membership and features in-depth articles on the Arboretum collections and history, as well as general information of interest to plant lovers in the Pacific Northwest and beyond. Join/subscribe today.
