Kindly sponsored by a member of the International Dendrology Society.
John Grimshaw (2016)
Grimshaw, J. (2016), 'Stewartia pseudocamellia' from the website Trees and Shrubs Online (treesandshrubsonline.
Tree to 15(–18) m, often much smaller. Bark smooth but exfoliating, mottled in different shades, branches greyish-brown, twigs often compressed, zig-zag when young, when white-hairy. Leaves 6–12 × 3–5 cm, obovate or elliptic, glabrous above, pilose with axillary tufts of hairs below, 6–7 pairs of veins, margins mucronate-serrate, apex acute to shortly acuminate, base acute to subcuneate; petiole 3–15 mm. Flowers solitary, held outwards; pedicel 1–6 cm; bracteoles cordate-orbicular, 4–6 mm, always shorter than sepals; sepals 8–12 mm, rounded, concave, with tuberculate margins, densely white-hairy; corolla pure white, 6–7 cm across (rarely larger, to 9–10 cm), lobes obovate, though often irregularly so, with an undulate margin; stamens arranged in 5 groups; styles 5, fused. Capsules conical or ovoid, pointed, 2.5 × 1.5 cm across, white-hairy. July (Japan). (Ohwi 1965; Hsu, Boland & Camelbeke 2008).
Distribution Japan North Korea South Korea
Habitat Mixed mountain forests, 175–1450 m asl.
USDA Hardiness Zone 4-7
RHS Hardiness Rating H5
Awards RHS AGM 2012
Conservation status Not evaluated (NE)
Stewartia pseudocamellia is generally considered to be the finest species of the genus in cultivation, and is the most commonly grown in both Europe and North America (Hsu, Boland & Camelbeke 2008). Not many trees combine so many good features so successfully; a comparatively slow growth rate, good habit, outstanding mottled bark in shades of brown-grey and burnt ochre, beautiful flowers produced profusely in summer, and autumn colour ranging from darkest claret to bright red-orange. In addition it is tolerant of the cold of New England or continental European winters, surviving –22° C on occasion, and thrives in a generally warm climate, though it does not enjoy prolonged heat as in the southeastern United States (Dirr 2009). For example S. pseudocamellia flowers well as a shrub in Norway, but in the Philadelphia area (for example) it can become a magnificent tree.
The species had been introduced from Japan to France by 1868 and to the United States prior to its arrival in Britain in about 1874 (Veitch 1906; Chittenden 1951). It is not clear how many specimens currently in cultivation are of Japanese origin, with the suggestion having been made (Hsu, Boland & Camelbeke 2008) that most are of Korean origin, possibly due to the Japanese plants being robust. There have been recent introductions from Japan, however, with SOJA 071 coming from Honshu in 1989 (in cultivation at Quarryhill), and BSWJ 11044 from northern Japan being commercially available in the UK. The large specimens recorded by Bean must have been of Japanese origin. The tallest recorded in the UK was a 17 m tree at Leonardslee, West Sussex, in 1968 (Bean 1981) while the current champion (2015) is a 15 m × 51 cm specimen at Killerton, Devon, measured in 2001 (Johnson 2011), which may be the same tree as that recorded at 15 m in 1970 (Bean 1981). In the United States, a tree of 13.7 m was recorded at Puyallup, Washington, in 1992 (Jacobson 1996), but it seems likely that there are many more trees that have attained or exceeded this stature now.
Selected at Polly Hill Arboretum from seedlings grown from seed collected from the Arnold Arboretum in 1966. It has down-sweeping branches (hence the name), vigorous growth, glossy foliage and flowers to 9 cm across (Polly Hill Arboretum; Hsu, Boland & Camelbeke 2008).
A pendulous clone selected at Polly Hill Arboretum, noted also for rich red-purple autumn colour (Polly Hill Arboretum).
Propagations from a plant received from the Hillier Nurseries by Philippe de Spoelberch at Herkenrode, and showing consistently excellent autumn colour (Hsu, Boland & Camelbeke 2008).
A large-flowered clone selected by Antoni Stepkowski, Bogacica, Poland (A. Stepkowski pers. comm. 2015).
Synonyms / alternative names
Stewartia koreana Nakai ex Rehder
Stewartia pseudocamellia 'Korean Splendor'
The first material of S. pseudocamellia to be introduced from Korea was seed collected on Chiri San, by Ernest Wilson in 1917, and cultivated at the Arnold Arboretum, where original trees still grow. It was admired there in 1930 by Arthur Osborn of Kew, and material reached England in the following year (Bean 1981). It rapidly became popular and plants of Korean lineage may now have supplanted Japanese stock in general cultivation (Hsu, Boland & Camelbeke 2008). Perceived small differences led to it being described as distinct, and a succession of synonyms has been applied, but it is generally considered that there are no significant distinctions between Japanese and Korean plants. There is some merit in recording the origin for horticultural purposes, however, as Korean trees may be slightly shorter, and are said to have flowers that open more widely than those from Japan; particularly good red autumn colours are also claimed for them (Armitage, Edwards & Lancaster 2014). As they are usually raised from seed they are best treated under the name Koreana Group – which has also been granted the RHS Award of Garden Merit. It has been reintroduced on several occasions in more recent times.
A Polly Hill Arboretum selection of the same origin as ‘Ballet’. It has consistently orange-red autumn colour and the original tree has silvery-grey and burnt amber bark. The flattened flower is up to 10 cm across, with a whorl of honey-coloured stamens (Polly Hill Arboretum; Hsu, Boland & Camelbeke 2008).
A Polly Hill Arboretum selection of the same origin as ‘Ballet’, named on account of the pale green ‘wash’ on the flowers (though this is sometimes found on other clones too) (Polly Hill Arboretum; Hsu, Boland & Camelbeke 2008).
A columnar clone with large flowers selected by Crispin Silva, Crispin’s Creations Nursery, Molalla, Oregon (C. Silva pers. comm. 2015).