Japanese stewartia blooms in late-spring and early summer in our region. (Photo by Niall Dunne)
BY CORINNE KENNEDY
Stewartia pseudocamellia is a lovely small tree, usually considered to be the finest Stewartia species in cultivation. With elegant small flowers, an attractive habit, delicate branching, showy exfoliating bark, and glowing fall colors, it’s highly attractive in all seasons—particularly in winter, when the color and architecture of its branching is fully revealed. In both North America and Europe, Japanese stewartia is the most commonly grown Stewartia species. With no serious insect or disease problems and a relatively slow growth rate, it’s an excellent choice for small residential gardens as well as public gardens and arboreta.
Until two years ago, the Seattle Japanese Garden contained just two specimens, one a mature tree in 1996 when it was transplanted there, the other a very young tree planted in 2003. Unfortunately, both were sited along a little-traveled path in the southwest corner of the Garden and are hidden from view behind other trees and shrubs. Not counting Japanese maples, Japanese stewartia is my favorite deciduous tree, so I was delighted when a new specimen was planted in 2023 just past the Garden’s entry gate in the Tateuchi Community Room’s courtyard!
The young specimen just inside the Japanese Garden entry gate. (Photo by Corinne Kennedy).
A Genus of Understated Beauty
“If there is a tree that embodies the Japanese principle of wabi-sabi, the intuitive appreciation of understated beauty, it is the genus Stewartia. This is evident from its graceful form, irreg-ularly mottled bark and demure white flowers. When the zenith of spring-flowering trees has passed, stewartias fill that quiet moment in early summer with their camellia-like flowers.” (from “Stewartia in Cultivation,” Hsu et al.)
Stewartia is comprised of approximately 20 species (authorities have varying opinions about this number), including both deciduous and evergreen trees, and some shrubs. The genus was once widespread around the globe, but is now restricted to two widely separated areas—East Asia and the southeastern United States. This divergent pattern, resulting from Ice Age climate change, is characteristic of other genera, such as Magnolia and Hamamelis. Fifteen species are native to China, three to Japan and the Korean Peninsula, and two to the U.S. Southeast.
Stewartia malacodendron, an American species, was first described in 1697, in the Reverend John Clayton’s “Account of Virginia.” Decades later, in 1746, Linnaeus created the genus, choos-ing the name Stewartia to honor John Stuart, the 3rd Earl of Bute, an amateur botanist who had planted that species in his London garden after it was intro-duced to Britain. (Stuart had also assisted with the founding of Royal Botanic Gardens, Kew.) Unfortunately, Linnaeus based his spelling of the genus on an incorrectly labeled painting of Stuart’s tree. Some authorities still use the spelling Stuartia, which was promoted by French botanist Charles L’Héritier and was widely used during the 19th century, especially in Britain. The rules of botanical nomenclature, however, prohibit correcting Linnaeus’s error.
The flowers open from plump, round buds.
Beautiful Form, Flowers, Foliage, and Bark
Stewartia pseudocamellia is an understory tree with a pyramidal or oval habit, native to the mountains of Japan, except on Hokkaido, the northernmost island. It is also native to the Korean peninsula. In the wild, trees are often seen growing along streams and in forest openings. This species has a long history in Japan as an ornamental—planted as a street tree, in parks, and near temples. The Japanese name, natsu tsubaki, means “summer camellia” and refers to the early summer flowers that resemble those of camellias. Similarly, the specific epithet (the second word of a botanical name) is pseudocamellia, which means “false camellia.” The resemblance is readily understandable: Both Stewartia and Camellia are members of Theaceae, the tea family.
Japanese stewartia may reach 60 feet tall in the wild, but it is usually considerably smaller in cultivation. Here in the Pacific Northwest, a mature size is about 25 feet tall by 12 feet wide (though some of the Arboretum’s specimens are about 35 feet tall; see sidebar). Deciduous, like other hardy stewartias, it has simple (undivided) leaves that are oval or lancelike in shape and finely toothed, appearing alternately on the stems. In autumn, the medium-green foliage is transformed into glowing oranges, reds, and/or purples. Although the trunk and branches of young trees are colored an unremarkable brown, the zigzag habit of the young branches is quite attractive. And with time, the bark peels, revealing a lovely patchwork of pink, tan, gray, cinnamon and plum. In winter, Japanese stewartia’s elegant branching and attractive bark are fully displayed.
Small, pure-white flowers open in early summer from plump, round buds. Cup-shaped and two to three inches wide, they consist of five overlapping petals with frilled edges and an inner ring of showy golden stamens. Flowers open over a period of about three to four weeks, rather than all at once, creating an extended display of delicate floral beauty. Fruits are brownish, woody capsules that burst open to release their seeds.
Fall color on the Japanese stewartia at the north end of Azalea Way. (Photo by Niall Dunne)
Introduction and Cultivars
Stewartia pseudocamellia was introduced to the United States in the late 1860s, and to Britain about a decade later. In the U.S., some of the oldest documented living specimens are planted in Harvard University’s Arnold Arboretum and have survived many decades of cold winters. Unlike some trees with attractive bark, includ-ing snakebark maples, their beautiful exfoliating bark has been retained, even with great age.
Since the introduction of Japanese stewartia to the West, many cultivars have been created. They include ‘Ballet’ (offering a graceful, spread-ing habit, down-swooping branches, glossy foliage, and larger flowers and fruits than the species), ‘Cascade’ (a slow-growing cultivar with a semi-weeping habit, cascading branches, and red-purple fall color), ‘Harold Hillier’ (providing excellent, reliable fall color, even in consider-able shade), and ‘Pink Form’ (a rare cultivar, with whitish-pink flowers that open from pink buds).
Taxonomic Disputes
Unfortunately, Stewartia pseudocamellia has been the subject of confusing taxonomic (classification) disputes! It turns out there are subtle differences between Japanese stewartia trees originating in Japan and those native to Korea. Considering the history of their intro-duction to the West, some authorities concluded that most specimens in cultivation outside of Asia are of Korean rather than Japanese origin. And, in 1926, Arnold Arboretum taxonomist Alfred Rehder published a new name for the Korean plants, Stewartia koreana, which he credited to Japanese botanist Takenoshin Nakai.
This name, acknowledging a new species, was retained until 1973, when the Arnold Arboretum’s new taxonomist, Stephen Spongberg, restored the name Stewartia pseudocamellia to the Korean trees. He contended that the differences Rehder described were not significant enough to establish a separate Korean species—or even classification as a taxonomic variety (indicated in botanical names by the abbreviation “var.”).
Close up of the fall color. (Photo by Niall Dunne)
One difference of some importance is that trees of Korean origin are slightly hardier than those from Japan. In addition, their flowers are described as larger and more saucer-like. I find it fascinating that a more recent genetic analysis (by Arnold Arboretum associate Jianhua Li and colleagues) showed that the Korean trees diverged from Japanese trees about ten million years ago!
Even now many sources continue to refer to Korean trees as a distinct species. Botanical names still in use include Stewartia koreana, Stewartia pseudocamellia var. koreana, and Stewartia pseudocamellia Koreana Group.
Cultural Needs and Growing Tips
Before describing the cultural requirements of Stewartia pseudocamellia, it’s useful to consider the genus as a whole. All species prefer moist, acidic soils, and most require light shade where afternoon sun is intense. Species native to the U.S. Southeast, however, need consistent summer warmth; those native to East Asia grow best under cooler maritime conditions. Pests and diseases are uncommon, but when soils are insufficiently acidic, leaves often exhibit chlorosis (yellowing, due to lack of chlorophyll), and drought conditions may result in areas of leaf necrosis (black or brown markings, from cell death). After late spring frosts, some stewartias may not flower.
Stewartia pseudocamellia is hardy to at least USDA Zone 5 (minimum temperature -20 degrees Fahrenheit). It grows best in light-to-open shade (or, in cooler climates, full sun)—and in moist, acidic, humus-rich, well-drained soil. Summers in our region are dry, unlike in Japan, so regular watering is needed.
I’m grateful that Japanese stewartia has done very well in my own garden—which, like the Seattle Japanese Garden, has poorly drained clay soil. My tree is growing in part shade, away from pavement and reflected heat, and is surrounded by other trees, shrubs and herbaceaous plants. I wonder how this species will adapt to climate change, but because of its resilience I’m optimistic about its survival in our region. I probably wouldn’t describe Japanese stewartia as wabi-sabi, a Japanese aesthetic concept that’s more nuanced than meaning simply “understated beauty,” but I love the graceful, year-round beauty it brings to the Seattle Japanese Garden—and to my garden as well. ❦
Fall foliage on mature specimen in the Tea Family Collection, along Arboretum Drive. (Photo by Niall Dunne)
Japanese Stewartia in the Arboretum
The larger Washington Park Arboretum collection boasts three specimens of Stewartia pseudocamellia and two specimens denoted as S. pseudocamellia var. koreana. They vary in age and size, and all originated from nurseries or private gardens within the U.S. The easiest to find is a young Japanese camellia received in 2017 and planted at the very north end of Azalea Way, just by the recently restored and relocated Tsutakawa Gates. In the autumn, the tree bears gorgeous, orange-red foliage—echoed by the fall color of a nearby Sargent’s cherry—and provides a stunning “come hither” to visitors at the main entry point to the park.
In the main tea family collection, just to the north of the New Zealand Forest, you’ll find three older and larger trees dating to the 1940s: the two koreana specimens and one specimen of the straight species. All are 35 feet tall, or thereabouts. The koreana specimens grow at the east edge of the camellia collection by Arboretum Drive, while the straight species is deep in the heart of the camellia grove, along its inner trail. Everything about these trees is amazing, from their red-to-purple fall color to their wonderful peeling bark.
Adapted from a post that first appeared on the Japanese Garden Blog, seattlejapanesegarden. org/blog.
Corinne Kennedy is a Garden Guide, fre-quent contributor to the Japanese Garden Blog, retired garden designer, and member of the
“Arboretum Bulletin” Editorial Board.
References
- Bean, W.J. “Trees and Shrubs Hardy in the British Isles, Vol V: 8th Edition Revised.” St. Martin’s Press, Inc. 1981.
- Grimshaw, John. “Stewartia pseudocamellia” (2016) from “Trees and Shrubs Online,” treesandshrubsonline.org.
- Hsu, Eric, Boland, Timothy; and Camelbeke, Koen. “Stewartia in Cultivation.” “The Plantsman.” June 2008.
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This article is reprinted from the spring 2026 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.
