Japanese Stewartia: Camellia-like Flowers in Early Summer and Glowing Fall Color

By Corinne Kennedy

Branches, leaves, and flower buds of a Japanese stewartia. (photo: Derek Ramsey, Wikimedia Commons) 

Stewartia pseudocamellia (Japanese stewartia) is a lovely small tree that’s attractive in all seasons—and one of my favorite deciduous trees! Until recently, though, the Seattle Japanese Garden’s trees were not prominently located. Two were planted along a little-traveled path in the southwest corner of the Garden, mostly hidden behind other trees and shrubs. So I was delighted when a new Japanese stewartia was planted this past winter in the Tateuchi Community Room’s courtyard, just past the Garden’s entry gate. 

The Genus Stewartia: 

The genus Stewartia was once widespread around the globe, but is now restricted to two widely separated areas—Asia and eastern North America. This divergent pattern, resulting from Ice Age climate change, is characteristic of other genera, such as Magnolia and Hamamelis. Stewartias native to temperate regions are deciduous, and most are small to medium-sized trees with delicate branching, early summer flowering and attractive fall color. (In tropical regions of Asia, however, some species are evergreen.) The genus name, Stewartia (sometimes spelled Stuartia), dates from 1746, nearly a century after Western botanists discovered an American species growing in Virginia. 

Recently planted Japanese stewartia in the courtyard outside the Tateuchi Community Room. (photo: Corinne Kennedy, June 2023) 

Stewartia pseudocamellia: 

Stewartia pseudocamellia is my favorite stewartia species and the one most widely cultivated throughout the world. Its Japanese name, natsu tsubaki, means “summer camellia” and refers to the early summer flowers that resemble those of camellias. Similarly, the second word of its botanical name (the species name) is pseudocamellia, which means “false camellia.” This resemblance is readily understandable: both Stewartia and Camellia are members of the tea family (Theaceae). 

Japanese stewartia is an understory tree with a pyramidal or oval habit, native to the mountains of Japan, except on Hokkaido, its northernmost island. It is also native to the Korean peninsula. In the wild, Japanese trees are often seen growing along streams and in forest openings, and may reach 50-60 feet tall. In cultivation, however, this species is usually considerably smaller. Here in the Pacific Northwest, the mature size (at 20-25 years) is about 25 feet tall by 12 feet wide. 

In Japan, Stewartia pseudocamellia has a long history as an ornamental, planted as a street tree, in parks, and near temples. 

The beautiful fall color of the Stewartia pseudocamellia specimen planted at the north end of the Arboretum’s Azalea Way. (photo: Niall Dunne, in the Winter 2018 issue of the Washington Park Arboretum Bulletin) 

Like other hardy stewartias, the leaves of Stewartia pseudocamellia are deciduous, undivided (simple), oval-shaped, and finely toothed, appearing alternately on the stems. In autumn, the medium green foliage is transformed into glowing oranges, reds, and/or purples. 

The peeling bark of a Japanese stewartia growing in Lublin, Poland. (photo: Salicyna, UMCS Botanical Garden, Wikimedia Commons) 

Finally, after the leaves of Japanese stewartia have fallen, the tree’s elegant branching and attractive bark are more fully displayed. 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. 

Closeup photo of Japanese stewartia’s foliage and flowers. (photo: Uleli, Wikimedia Commons) 

The 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. 

Japanese stewartia is hardy to USDA Zone 5 (minimum temperature -20 degrees F), and has no serious pest or disease problems. It grows best in light to open shade (or even, in cooler climates, full sun)—and in moist, acid, humus-rich, well-drained soil. Summers in our region are dry, unlike in Japan, so regular watering is needed. 

For Plant Geeks—A Taxonomic Digression: 

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 introduction to the West, some authorities concluded that most specimens in cultivation outside of Asia are of Korean rather than Japanese origin. And in 1926, an 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.). One difference of some importance is that trees of Korean origin are slightly hardier than those from Japan. 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. 

For Interested Gardeners—A Recommendation: 

Stewartia pseudocamellia is a lovely small tree usually considered to be the finest stewartia species in cultivation. With no serious insect or disease problems and a relatively slow growth rate, it’s an excellent choice for small residential gardens. Elegant small flowers, an attractive habit, delicate branching, showy mottled bark, and glowing fall colors make it highly attractive in all seasons—and particularly in winter, when the color and architecture of its branching is fully revealed. 

[Note: This article is an adaptation/expansion of my 2019 blog article about Stewartia pseudocamellia and another stewartia species, Stewartia monadelpha.] 

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