Camellia oleifera is a Cold-hardy Species with Fragrant White Flowers in Autumn

By Corinne Kennedy

Camellia oleifera in bloom in the Seattle Japanese Garden. (photo: Aleks Monk, Oct. 2014)

Camellia oleifera is a cold-hardy species of camellia with 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, planted 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 received from Nanjing, China. The Garden’s specimen was derived from this accession and planted in 1970. It was later moved to its current location.

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, also spelled Kamel, a 17th century German Jesuit missionary, pharmacist and naturalist who served in the Philippines.)

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. The hardiest species in the genus Camellia, its native range extends further north than the range of any other species. In China, it’s been widely cultivated for more than 2,300 years for the edible oil pressed from its seeds. Known as tea seed oil or camellia oil, it’s 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.

Photos of camellia oil and the fruits and seeds of Camellia oleifera, from a scientific article: “Camellia oleifera “Xianglin 14’ produced abundant fruit. Fruit diameters were up to 4 cm (A); seed appearance at seed shell opening (B); a mix of seeds, nutlets, and fruit (C); and tea oil derived from seeds (D).” (photos and caption: Yongzhong Chen, Baoming Wang, Jianjun Chen, Xianguan Wang; Frontiers in Plant Science,  March 2015; Creative Commons 4.0)

After the mature seed pods crack open, the seeds are pressed into a high-temperature oil, used in Asian countries not only 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.

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.

The lovely white flowers of Camellia oleifera, planted in the Seattle Japanese Garden next to the original East Gate. (photo: Corinne Kennedy, Nov. 2020)

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—or sometimes entirely pink. Opening in fall and early winter, blooms are 2-3 inches wide, with 5-7 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 sufficient water and protection from reflected heat, it tolerates full sun here in the Pacific Northwest. It’s hardy to USDA Zone 7 (minimum temperature 0 degrees Fahrenheit) but established plants may tolerate slightly colder temperatures 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.

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—cultivars 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 include 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’re 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 the history of Camellia oleifera fascinating—for its usefulness in breeding camellia cultivars with improved hardiness and garden characteristics as well as for the centuries-long importance of its oil. Ultimately, though, I love the elegant simplicity of its single, fragrant flowers and the beauty they bring to this season of transformations.

Corinne Kennedy is a Garden Guide, a frequent contributor to the Seattle Japanese Garden blog, and a retired garden designer.