genus profile Stewartia pseudocamellia ‘Mint Frills’ has been selected for its ruffled petals and green tinged flowers Timothy Boland Timothy Stewartia in cultivation Er i c Hs u , Ti m o th y Bo l a n d and Ko E n ca m E l beke provide an overview of the cultivated species and highlight some new cultivars f t h e r e i s a t r e e that embodies their camellia-like flowers. Their that the genus is in the Theaceae, along the Japanese principle of wabi- preference for acidic soils notwith- with other ornamental genera such Isabi, the intuitive appreciation standing, they are suitable subjects as Camellia, Franklinia and Schima. of understated beauty, it is the genus for small gardens since their growth, Depending on taxonomic point of Stewartia. This is evident from its at best, is modest. view, Stewartia encompasses approx- graceful form, irregularly mottled imately 20 species. However, the bark and demure white flowers. Genus characteristics genus has a surprisingly wide geog- When the zenith of spring-flowering The solitary white flowers of raphical distribution, from the moist trees has passed, stewartias fill that Stewartia convince any botanically mont ane forests of China into the quiet moment in early summer with inclined or knowledgeable gardener Japan ese archipelago, and to the 78 June 2008 PlantsmanThe Taxonomic history The earliest reference to the genus is attributed to Reverend John Clayton’s Account of Virginia in 1687 in which he described a tree on Archers Hope Creek, near Williamsburg, Virginia (Baldwin 1969, Spongberg 1974). The genus was introduced to cultivation about 50 years later, to the Fulham garden of the English traveller and naturalist Mark Catesby, who receiv- ed S. malac odendron from another John Clayton, an English naturalist in Virginia. It flowered in 1742 and he passed plants to John Stuart, the 3rd Earl of Bute who was assisting with the founding of the botanical garden at Kew. Linnaeus later acquir- ed dried specimens upon which he honoured John Stuart – the nomen- clatural confusion began here because Linnaeus was misled about the spelling of his name and publish- ed it as Stewartia. The spelling Stuartia is used by some authorities, Timothy Boland Timothy and nomen claturist Dick Brummit Stewartia pseudocamellia is usually regarded as the best species for autumn colour (pers. comm.) has long petitioned to adopt this spelling. ecolog ically-rich river corridors of on the species. One to two bracteoles The majority of species are native the southeastern United States. All usually subtend the calyx. The woody to China; the Flora of China (Shu but the subtropical species are in brown fruit capsules can persist on 2007) recognises 15, four of which cultivation, equally at home in the the branches for a year or more are in cultivation. The rest await intro- cold climate of Massachusetts as before being shed. duction; a few may be too tender for they are in the mild regions of All the species discussed here temperate gardens, while others may western Britain. are deciduous except S. calcicola, not offer much horticultural merit. They are either evergreen or deci- S. laotica and S.pteropetiolata. Autumn Three species are recognized from duous trees (rarely shrubs) and are colour is one of the striking Japan, Korea and surrounding islands, best known for the smooth, mottled, characteristics of most Stewartia. and two from southeast USA. Spong- exfoliating bark of some species, Plants in the eastern US and Belgium berg’s review of the deciduous species although in some it is fissured and in have revealed the same sequence of (1974) remains the most comprehen- others it is drab and unremarkable. autumn colour in the following order: sive, although a full monograph of The alternate leaves are ovate or S. serrata, S. malacodendron, S. pseudo­ the genus has yet to be published. elliptic with serrate margins, the camellia, S. rostrata, S. sinensis, S. mona­ Phylogenetic relationships have pubescence varying from none to delpha and S. ovata. Stewartia malaco­ been examined (Li 1996), including moderate. The 5-petalled flowers dendron and S. ovata generally have the use of DNA data (Prince and look similar across the genus but disappointing autumn colour, Parks 1997, Li et al. 2002), but this differ significantly in size. Depending although S. ovata may turn yellow. needs additional work since the rel- on the climate, they open between Stewartia pseudocamellia is the most ationship between the New World late May and late June. The stamens reliable for autumn colour. The and Old World taxa is uncertain, and are numerous yet their filaments can hybrids have intermediate timing, the majority of Chinese species have be white, purple, or yellow, depending depending on their parentage. yet to be included. ➤ June 2008 79 genus profile Stewartia calcicola availability in commerce. was selected for its 5cm wide flowers This evergreen species, a native of Several self-sown seedlings at the with red-streaked petals and purple forests at 900–1,700m in southwest Polly Hill Arboretum and Arboretum stamens. However, this ornamental Guangxi and southeast Yunnan, Wespelaar have characteristics akin feature is not necessarily unique as it China, is scarce in cultivation. It to S. x henryae. They can display is not uncommon among plants in is readily dis tinguishable from the excellent autumn colour. the wild. Only one existing specimen other evergreen species by its of S. malacodendron ‘Delmarva’ exists pubescent leaf midveins and Stewartia laotica at the Polly Hill Arboretum since bracteoles nearly one half as long as Restricted to Guangxi and southeast repeated efforts to propagate it by the sepals. The small to medium- Yunnan, China, as well as Laos and cuttings have failed. sized flowers are not as showy as Vietnam at 900–1,800m, S. laotica is those of S. pseudocamellia. an evergreen species recently introdu- Stewartia monadelpha There is a containerised specimen ced in 2006 from northern Vietnam, Distributed through the mountain- at Arboretum Wespelaar and Garden collected at 1,900m (Peter Wharton ous south-central Honshu, Kyushu, of Herkenrode, Belgium, which until pers. comm.). Its performance in and Shikoku, Japan, S. monadelpha recently spent the winters in the Western cultivation is not known. has small, delicate flowers. These glasshouse. It has now been planted would be overlooked if they were out and has survived its first winter Stewartia malacodendron not borne in such profusion, on outside without frost damage. It Found in sparse populations in the established trees. Even the bracteoles roots easily from cuttings, which south eastern US from Virginia to can be attractive, resembling green have been distributed to other Florida and west to Mississippi, butterflies before the flowers open. institutions with milder climates. Louisiana, and Arkansas, as well as Although the bark may not be as To date, it has not been trialled Texas, S. malaco dendron has spectac- polished as S. pseudocamellia or outside in Europe. ular flowers – the white petals set off S. sinensis, it peels to reveal a by red-purple stamens. It is rarely handsome cinnamon-red colour. Stewartia x henryae seen in western Europe since late The diminutive size of the flowers, This hybrid first occurred as a spont- spring frosts tend to debilitate it and fruit and leaves belies the size of aneous cross between S. monadelpha the summers are not hot enough to mature trees in the wild. During and S. pseudocamellia at the Henry ripen the wood. In such conditions it his expedition in February 1914, Foundation for Botanical Research, is best to provide a protected, part- plant collector Ernest Wilson Gladwyne, Pennsylvania, and descr- ially shaded location. At Herkenrode, photographed several large trees ibed in 1964. It is distinguished from Belgium, a plant is flourishing under- growing with Trochodendron aralioides the latter parent by the larger bract- neath Sequoia sempervirens and on Yakushima island; one in his eoles not adpress ed to the sepals and between rhododendrons. At the photograph measured 17m tall and the smaller petals. The bark is inter- Arnold Arboretum, Massachusetts, 2.5m diameter at breast height. The mediate between its putative parents. plants either fail or dieback due to de Belder family in Hemelrijk, Spongberg (1974) remarked that the region’s cold winters. Belgium, have a core piece of a 300- the flowers of S. x henryae are indicat- Stewartia malacodendron ‘Delmarva’ year-old specimen from Yakushima. ive of S. monadelpha, but reserved (Huttleston 1993) was raised from However, trees in cultivation do not judgment on its hybrid status until wild seed collected on the Delmarva approach the scale of their wild cytological and controlled hybrid- Peninsula by Jacque Legendre and counterparts as they grow isation studies are carried out. How- given to Polly Hill (founder of the moderately. ever, he identified one of the seed- eponymous arboretum) by Legendre’s Stewartia monadelpha is the last lings raised at Polly Hill Arboretum, friend William Frederick, a Delaware hardy deciduous species to colour in Massachusetts, as S. x henryae, which plantsman. A sibling of ‘Delmarva’ autumn. The presence or absence of has been named ‘Skyrocket’ (Huttl- still survives in the Frederick garden. summer heat can determine the eston 1993). Stewartia x henryae Hill was able to grow two plants autumn colouration; plants with ‘Skyrocket’ has enormous potential from the eight seeds she received; longer growing seasons often turn for narrow spaces due to its fastigiate one died after being girdled by mice scarlet, while those with shorter habit, but it has been difficult to in 1971 while the other flowered growing seasons tend towards propagate, thereby limiting its after 27 years from seed. The cultivar purple. Nonetheless, S. monadelpha / GPL 7 Mark Bolton Boland; 4 Timothy 3, 6 Philippe de Spoelberch; 1, 2, 5, 80 June 2008 1 2 3 5 4 1 Stewartia sinensis, at Lushan, China 2 S.