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 mont­ane forests of China into the quiet moment in early summer with inclined or knowledgeable gardener Japan­ese archipelago, and to the

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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. malac­odendron 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 nomen­claturist Dick Brummit Stewartia pseudocamellia is usually regarded as the best species for autumn colour (pers. comm.) has long petitioned to adopt this spelling. ecolog­ically-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 dis­tinguishable 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 south­eastern 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. malacodendron­ 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 adpress­ed 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,

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3 5

4 1 Stewartia sinensis, at Lushan, China 2 S. sinensis, a clone with particularly fine bark at Trewithen Gardens, Cornwall 3 S. ovata 4 S. monadelpha 5 S. malacodendron 6 S. rostrata, at Lushan, China 6 7 S. pseudocamellia 7 ➤

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2 3

4 5

6

7 8 9

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has demonstrated excellent heat Arboretum Wespelaar and Garden seem constant nor significant tolerance and full sun exposure. of Herkenrode has been disappoint­ enough to justify recognition at Stewartia monadelpha ‘Black Dog’ ing for the flowers tend to shed as specific, varietal or cultivar group has been selected for its dark purple quickly as they open, and in some level. Attributing plants with traits foliage, which may appear black instances, may fail to open at all. of the Korean populations to ‘Korean under certain light. Two varieties are recognized—var. Splendor’ is problematic, given the ovata with yellow stamen filaments inclusion and variability of plants Stewartia ovata and var. grandiflora with purple raised from open-pollinated seed As with S. malacodendron, this species stamen filaments. distributed by nurseries. is restricted to the southeastern US, The cultivars ‘Red Rose’, ‘Royal However, such taxonomic from Florida and Virginia in the east, Purple’ and ‘White Satin’ (Huttle­ problems should not obscure the westwards to Mississippi. Spongberg ston 1993) to some extent represent horticultural merits of S. pseudo­ (1974) stated that S. ovata and S. natural variation in stamen colour in camellia. Along with S. sinensis, the malacodendron reputedly overlap in wild populations. Although these bark of S. pseudocamellia ranks as the range. This overlap was recently cultivars should not be dismissed, best in the genus and is consistently confirmed by the Stewartia Working the authors caution that variants cited in articles praising ornamental Group in autumn 2007 who within populations should be observ­ tree bark. One cannot deny its visual observed these two species growing ed carefully before considered for and tactile pleasures—the mottled in tandem in the Bankhead National cultivar distinction. shades of brown, grey and burnt Forest, Winston County, Alabama ochre comb­ined with the feel of and collected seed. Stewartia pseudocamellia polished alab­aster. Although they do This species is readily recognised If there is one species frequently not open simultaneously for a by its winged petioles which hide the encountered in cultivation, it is magnificent display, the 9–10cm buds, separate styles and a single S. pseudocamellia, native to Japan and wide, creamy white flowers with a bracteole. As long as a long growing Korea. In Japan, it grows in open to boss of yellow stamens are produced season and adequate vernalisation is dense mixed woodland of Acer spec­ prolifically over a long period before ensured, S. ovata is an equal, if not ies, Clethra barbinervis, Enkianthus dropping from the branches. It is a better, contender to its American campanulatus, Pinus densiflora, Quercus striking sight to see the shed flowers cousin, for it is exceptionally hardy (a acuta and Q. serrata, between 175 and carpet­ing the ground beneath a tree. tree grew in a Michigan garden 1,450m. In South Korea, S. pseudo­ Autumn colour ranges from darkest (Zone 5, -26 to -29°C)). The large camellia is found in similar habitats claret to bright red-orange. white flowers, 5–10cm wide, have with Acer species, Aralia elata, Hydr­ The Arnold Arboretum of beautifully ruffled petals and an angea serrata and Viburnum species. Harvard University may have the attractive boss of stamens. The The Korean and Japanese oldest, documented living specimens varying rate with which the flowers populations are a taxonomic of S. pseudocamellia, which are open prolongs the display. quandary due to their superficial descended from Korean collections Interestingly, trees at the Polly Hill similarities and subtle differences; by Ernest Wilson in 1918. Their Arboretum possess darker green Korean populations have been survival through nine decades of foliage than those in the wild, which treated as S. koreana, S. pseudocamellia Boston’s vicarious winters attests may exhibit chlorotic foliage, a var. koreana, S. pseudocamellia to their remarkable hardiness. possible symptom of drought stress. Koreana Group and S. pseudocamellia Unlike the snake-bark maples,

1, 2, 3, 5, 7, 8, 9 Philippe de Spoelberch; 4, 6 Timothy Boland Presumably, due to the area’s ‘Korean Splendor’. It is thought that whose much-prized striated bark maritime climate, its performance at the majority in cultivation are of may disappear with age, the Korean origin, whereas those of venerable Arnold specimens still 1 S. sinensis Japanese origin are rare due to their retain their beautiful mottled,­ 2 S. serrata less robust constitution. However, exfoliating bark. At the Polly Hill 3 S. pseudocamellia, a variant with bullate leaves 4 S. malacodendron ‘Delmarva’ the differences­ between Korean and Arboretum, an old S. pseudocamellia, 5 S. monadelpha Japanese populations cited in the acquired from Brooklyn Botanic 6 S. ovata literature, whether they be autumn Garden and planted in 1961, is already 7 S. rostrata 8 S. malacodendron colour, zigzag orientation of the showing similar characterist­ics to 9 S. pteropetiolata branches, or flower form, do not those at the Arnold Arboretum. ➤

June 2008 83 genus profile

It would be interesting to survey unique as it μdoes occur in other the genetic variation of S. pseudocam­ plants of this species. The original ellia in cultivation and determine tree at Polly Hill Arboretum is 12m whether they are descended from high with two trunks and a spread of one or two clones at the Arnold 8.8m. Arboretum. There is a need to Stewartia pseudocamellia ‘Harold expand and diversify the number of Hillier’, originating from the Hillier wild-origin S. pseudocamellia from Nurseries, UK, and named by Philippe Korea. Polly Hill Arboretum, de Spoelberch, Herkenrode, Belgium, Quarryhill Botanical Garden, in has excellent, reliable autumn colour California, and Royal Botanic under various light conditions, incl­ Garden Edinburgh have recently uding shade. introduced seed from Japanese One of the seedlings at Arboretum populations. Quarryhill has one of Wespelaar and Garden of Herkenrode Boland Timothy Stewartia ‘Scarlet Sentinel’ (above), named for its the few older plants, collected at raised from seed wild-collected at columnar habit and red filaments, andS. mona­ 1,210m in Honshu, Japan in 1989. Chiri San, South Korea, has proved delpha ‘Black Dog’ (right), with purple leaves Stewartia pseudocamellia ‘Ballet’ is to be distinctive in its shrubby habit, the best of three seedlings named by zigzag and reddish branches, and Gardens, Hobart, Tasmania, where Polly Hill Arboretum from open- excellent hardiness. Worth naming, the small to medium-sized flowers pollinated seed collected at the it has struck readily from cuttings, a are followed by attractive red fruits. Arnold Arboretum in 1966. It was noteworthy characteristic for a genus originally registered as a cultivar of notoriously difficult to propagate. Stewartia rostrata S. koreana (Dudley 1984). The original Several vigorous and tree-like This species was first introduced in tree is 14m in height, 30cm diameter plants at Arboretum Wespelaar and 1936 to the US via the Lu Shan at breast height, and has a canopy Garden of Herkenrode have single Botanic Garden, China, and a plant spread of 10m. It flowers in July with vertical stems and prominently from this introduction can be seen at 9cm wide flowers. The larger fruits, bullate leaves. They have not been the Arnold Arboretum. However, it longer shoots, and glossier leaves named but the leaves may have was not regarded as distinct from underscore the robust vigour of thicker cuticles and more sun S. sinensis until Spongberg’s review ‘Ballet’, and the grace with which the tolerance. (1974). It was first collected by Ernest branches sweep down led to the Wilson in Kiangsi Province, China, choice of name. Stewartia pteropetiolata but the herbarium specimens were Stewartia pseudocamellia ‘Milk and This evergreen species is restricted mixed with those of S. sinensis under Honey’ was first registered in 1992 to forests at 1,200–2,600m in the same collection number of 1722. under S. koreana (Huttleston 1993). south and west Yunnan, China, It can be distinguished from It originated from seed harvested in and Vietnam. There is one young S. sinensis by its twisted sepals, fruits 1966 at the Arnold Arboretum and plant, grown from seed collected at that are globose, mostly glabrous and differs from the typical species in Luchun, south Yunnan, at approxim­ abruptly beaked with four as opposed having 10cm wide, ruffled, white ately 2,100m, recently planted in to two seeds per chamber, and unrem­ flowers with a boss of yellow stamens the David C. Lam Asian Garden at arkable bark. Stewartia rostrata has a that are held flat rather than cupped. the University of British Columbia widespread distribution in China The autumn colour is a radiant orange- Bot­anical Garden, Vancouver, where it is found along streams in ­red that contrasts handsomely with Canada. According to the Curator, forests at 600–1,500m in Anhui, the silvery and burnt umber exfoliat­ Peter Wharton, it has survived -5°C Henan, Hubei, east Hunan, Jiangxi ing bark. The original tree is 12m with­out leaf damage. Wharton and Zhejiang. high with three main stems and a believes that the Vietnam­ese Flowering in May, it is one of the canopy spread of 9m. populations are likely to be hard­ier earliest Asiatic species to flower. The flowers of S. pseudocamellia than those in China. The flowers are 3–5cm in diameter ‘Mint Frills’ (Clemants 1997) are Older, flowering specimens can and the immature red fruits and lightly washed with pale green. How­ be admired at Villa Taranto, Italy, reddish tinged foliage are compensat­ ever, this distinguishing trait is not and the Royal Tasmanian Botanical ion for its rather nondescript bark.

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being short-lived, have a demure gardens of Trewithen, Wakehurst daintiness. Place and Borde Hill. This was Stewartia serrata ‘Pendula’ has a probably the one that Bean (1981) weeping habit but unfortunately the described as ‘smooth as alabaster flowers are concealed beneath the and the colour of weathered branches. A specimen can be seen at sandstone.’ In woodland areas near Arboretum Kalmthout but efforts to Lushan Bot­anical Garden, China, propagate it have not been successful. S. sinensis resembles S. monadelpha in its mott­led bark and conical and Stewartia sinensis pubescent seed capsules; age does Of the deciduous species, S. sinensis is not seem to influence bark rare in cultivation and typically appearance since a 300-year-old mistaken for other species. A grove tree on Hanpo Pass, Lushan, had labelled S. sinensis at the University of rather mottled bark (de Spoelberch Washington Botanic Garden, pers. comm.).

Philippe de Spoelberch Seattle, are likely to be S. x henryae. Stewartia sinensis ‘Panache’ is Plants grown from seed acquired in variegated with speckled leaves, The autumn colour can be a pleasing 1934 from Sun Yat Sen Memorial but it is perhaps better known as rich scarlet. Trees reach up to 12m in Park in Nanking, China, and initially a horticultural curiosity. the wild but the largest documented labelled as S. monadelpha at the Arnold Stewartia sinensis ‘Mei Lu Shu’ in cultivation (Seattle, Washington Arboretum were later recognized as (Clemants 1997) was one of two State) are between 7 and 7.6m S. sinensis. De Spoelberch (2002) seedlings raised at the Polly Hill (Jacobson 1996). reported that young plants are not Arboretum from seed harvested at Stewartia rostrata has shown readi­ very hardy, which may explain its the Arnold Arboretum in November ness to hybridise with other species, rarity. Likewise, its status in China 1984. When it first produced its particularly S. sinensis. Adam Wheeler may be vulnerable as it is scattered in 4cm wide white flowers in June of Broken Arrow Nursery, Connect­ forests at 500–2,200m in the central 1993, Polly Hill’s grandson, icut, is currently evaluating several and eastern provinces. Del Tredici et Alexander Hill, suggested the name hundred open-pollinated seedlings al. (1995) witnessed on Wudang Shan, that means ‘beautiful tree’ in from this species, some of which are Hubei, at 1,100m a magnificent spec­ Mandarin Chinese. Because ‘Mei showing intermediate characters. imen 15m tall and 55cm in diameter Lu Shu’ was raised from seed of Plants in cultivation are variable – at breast height and remarked that cultivated origin, it would be some are reluctant to flower even it was a sacred tree where Taoist interesting to determine whether after 15 years and 8m tall, so there is pilgrims offer and burn consecrated it is a hybrid or a pure species. a need to select a good floriferous paper symbolising money. clone. Those in Europe are often Appearing before S. pseudocamellia, Stewartia ‘Purple Lance’ propagated and sold as S. gemmata, a the 5–6cm wide flowers are borne This cultivar is reputed to be a synonym of S. sinensis, when they are profusely, but their impact is hybrid between S. monadelpha and actually S. rostrata. lessened by their failure to open S. rostrata, the original specimen is in Stewartia rostrata ‘Hulsdonk Pink’ fully. The Flora of China (Shu 2007) the garden of Karl E Flink, Bjuv, is reputed to have pink flower buds recognizes four varieties, which are Sweden. Initially dark purple at the that open to a pink-tinted flower. differentiated by shape, size, and beginning of the summer, the leaves texture of the petioles, bracteoles eventually assume a handsome, dark Stewartia serrata and sepals: var. acutisepala, var. green, glossy veneer. ‘Purple Lance’ This Japanese species is the first brevicalyx, var. shensiensis and var. is floriferous, but the flowers can be Stewartia to come into leaf and flower. sinensis. This variation may account obscured by the leaves. It has reddish young shoots, serrate for the differences seen among trees leaves with red petioles, and regular, in Europe and US compared to those Stewartia ‘Scarlet Sentinel’ reddish bracteoles that are similar in in China. A variant with particularly This cultivar is perhaps the best size to the sepals. The flowers are bell-­ attractive bark that should be documented and confirmed hybrid shaped and pendent, and despite conserved can be seen in the UK between S. ovata f. grandiflora and ➤

June 2008 85 genus profile

S. pseudocamellia. It arose as a chance after the completion of two seedling in the Chinese Path area at expeditions to Japan and one to the the Arnold Arboretum (Del Tredici southeastern US. and Li 2002, Del Tredici 2003). In addition, the Polly Hill Arbor­ Originally destined for an etum is part of the new collaborative Arboretum plant sale, it was taken Stewartia Working Group (SWG) and cultivated by Peter Del Tredici which consists of the following in his garden at Harvard, members: Mt. Cuba Center, Massachusetts. The hybrid nature Delaware; Birmingham Botanical was not revealed until the tree Gardens, Alabama; Yew Dell flowered 12 years later. With its Gardens, Kentucky; and Smithgall nearly columnar habit, 6.5m high Woodland Garden (Atlanta Philippe de Spoelberch with a 2.5m spread in 12 years, the Botanical Garden), Georgia. This Stewartia rostrata is distinguished by its wavy- original plant, now at least 9 x 5m, group will focus on the conservation edged sepals and the red fruit is one of its ornamental characteristics has proved to be an ideal plant for of the two North American species. small gardens. From late June to Other institutions where Stewartia In the UK, High Beeches Gardens early July, large white flowers with can be seen include the Morris holds the National Plant Collection prominent scarlet filaments nearly Arb­oretum, Pennsylvania; the of Stewartia, although other gardens obscure the leaves. Although not as Scott Arboretum, Pennsylvania; in the area, such as Wakehurst Place, showy or attractively mottled as its the Univ­ersity of Washington Borde Hill and Nymans have respect­ parent S. pseudocamellia, the grey- Botanic Garden, Washington able, if not venerable, specimens. brown bark does exfoliate in thin State; Quarryhill Bot­anical Garden, Despite the youth of the trees, strips up to 5mm wide. Any fruits California; and the University of Arboretum Wespelaar and Garden that form soon abort. British Columbia Bot­anic Garden, of Herkenrode, Belgium, has an Vancouver, Canada. impressive collection with some Significant collections in of the species planted as groves. North America and Europe Because Stewartia hybridise In the US, the Arnold Arboretum, readily in cultivation it is important Massachusetts, and the Polly Hill that reference collections with well- Arboretum, Massachusetts, hold the documented specimens of known North American Plant Collection wild provenance exist. Institutions Consortium collection of Stewartia. that propagate plants from open- Much of the collection at the former pollinated seed for sale or distrib­ originated from Ernest Wilson’s ution need to be aware that they gatherings in Korea and China, as may have hybrids on their hands. well as subsequent expeditions by the Arboretum staff through Conservation institutional relationships with The conservation status of the Chinese botanic gardens. Chinese species is not well known, The latter collection began as a although habitat degradation by result of Polly Hill’s visits to the human activity such as farming, Arnold Arboretum and her link with logging or mining threatens many the Delmarva Peninsula. In the populations. American species are maritime climate and sandy acidic vulnerable or endangered; the severe soils of the Polly Hill Arboretum, drought in the southeast US, Stewartia have performed particularly Georgia, has added exceedingly well (Boland 2006). considerable stress to populations Although the collection is largely that may already suffer from composed of taxa of cultivated inbreeding depression. Very few Philippe de Spoelberch origin, it is due to be augmented by Stewartia pseudocamellia ‘Harold Hiller’ colours occurrences of seedling regeneration those of wild documented origins well in the autumn, even in relatively shady sites were observed during the SWG

86 June 2008 PlantsmanThe autumn 2007 expedition. can take four years to germinate are three or more years of age. Cultivation (Jack Johnston, pers. comm.). Conclusion The east Asian species generally Spontaneous seedlings, especially of Stewartia may not have the robust perform better in cool maritime S. monadelpha and S. pseudocamellia showmanship of Magnolia, Malus or regions, whereas those from the hybrids, often arise near parent trees, Prunus, yet this deficiency is made up eastern US require consistent whereas attempts to raise them in for by their ornamental merits at all summer warmth. All species prefer pots are rarely successful. Of the seasons. moist, acidic soils, and need light deciduous-leaved species, S. shade if the afternoon sunlight is pseudocamellia, S. monadelpha and intense. Their foliage will often S. sinensis appear to be the least Er i c Hs u is a doctoral student exhibit chlorotic symptoms if soil difficult. studying conifers at University of pH is unsatisfactory, and it can One of the crucial factors for the Tasmania, Hobart, Tasmania, become marked by necrosis during survival of seedlings and cuttings Australia severe droughts. In rare instances may be the pH of the potting where late spring frosts have medium or irrigation water (Del Ti m o th y Bo l a n d is Executive occurred, stewartias may not flower Tredici, pers. comm.), and research Director of The Polly Hill at all. Pests and diseases are not is being undertaken on this. Arboretum, Massachusetts common in cultivation. Young cuttings or seedlings have to be protected from frost until they Ko e n Ca m e l beke is Director of

Propagation references Despite research into propagation Baldwin, J (1969) A seventeenth pseudocamellia ‘Ballet’. AABGA protocols (Curtis et al. 1996, Struve century record for Stewartia. Rhodora Bulletin 18: 117 and Lagrimini 1999), Stewartia 71: 434–438 Huttleston, D (1993) International remains scarce and expensive in the Bean, WJ (1981) Trees and Shrubs registration of cultivar names for nursery trade. It is typical for soft­ Hardy in the British Isles. 8th ed. unassigned woody genera 1992. wood cuttings taken in spring to St Martin’s Press, New York HortScience 28(4): 278–279 root successfully, only to suffer high Boland, T (2006) Stewartia collection Jacobson, A (1996) North American mortality­ after overwintering. How­ at the Polly Hill Arboretum. Public Landscape Trees. Ten Speed Press, Garden 1: 42–43 Berkeley ever, a 50% success rate can be ach­ Chang, H (1982) Stewartia yunnanensis. Li, J (1996) A systematic study on the ieved if a young mother plant is used. Acta Sci. Nat. Univ. Sunyatseni 4:77 genera Stewartia and Hartia (Theaceae). Stewartia rostrata and its hybrids are Clemants, S (1997) International Acta Phytotax. Sin. 34: 48–67 generally the easiest to propagate. registration of cultivar names for Li, J, Del Tredici, P, Yong, S & Propagation from seed is more unassigned woody genera 1996. Donoghue, M (2002) Phylogenetic difficult than that from cuttings. HortScience 32(4): 587 relationships and biogeography of Seed needs to be as fresh as possible Curtis, DL, Ranney, TG, Blazich, Stewartia (Camellioideae, Theaceae) inf­ FA & Whitman, EP (1996) Rooting erred from nuclear ribosomal DNA ITS and no single treatment is best; it and subsequent overwinter survival sequences. Rhodora 104: 117–133 of stem cuttings of Stewartia ovata. Prince, L & Parks, C (1997) Evolution­ acknowledgements J. Environm. Hort. 14: 163–166 ary relationships in the tea subfamily Tom Clark (Polly Hill Arboretum), de Spoelberch, P (2002) Les stewartias Theoideae based on DNA sequence Philippe de Spoelberch (Herkenrode à feuilles caduques rustiques en Europe data. Int. Camellia J. 29: 130–134 and Arboretum Wespelaar), Peter de l’Ouest. Belgische Dendrologie Belge Shu, ZJ (2007) Stewartia. In: Flora of Del Tredici (Arnold Arboretum), 2001: 8–22 China Editorial Committee (eds) Flora Jack Johnston (Georgia, USA) Del Tredici, P, Meyer, P, Hao, R, of China vol. 12. Science Press, Beijing, Abraham Rammeloo (Arboretum Mao, C, Conrad, K & Thomas, RW and Missouri Botanical Garden Press, Kalmthout), Thomas Ranney (North (1995) Plant collecting on Wudang St Louis Carolina State University), Stephen Shan. Arnoldia 55(1): 12–20 Spongberg, SA (1974) A review of Spongberg (Polly Hill Arboretum), Del Tredici, P & Li, J (2002) Stewartia deciduous-leaved species of Stewartia Jef Van Meulder (Arboretum ‘Scarlet Sentinel’. HortScience 37(2): (Theaceae). J. Arnold Arbor. 55: 182–214 Bokrijk), Diane Van Strydonck-de 412-414 Struve, DK & Lagrimini, LM (1999) Belder (Hemelrijk), Peter Wharton Del Tredici, P (2003) Stewartia Survival and growth of Stewartia (UBC Botanical Garden), Adam ‘Scarlet Sentinel’. Arnoldia 62(3): 16–22 pseudocamellia rooted cuttings and Wheeler (Broken Arrow Nursery). Dudley, T (1984) Stewartia seedings.J. Environm. Hort 17: 53–56

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