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Description: Shrub or tree to 24 m. Leaves 8.7-22.5 × 3.8-11.4 cm, ovate-oblong, elliptic, or obovate to oblanceolate, adaxially dense soft indumentum or hairy becoming glabrous with age, abaxial surface sparsely hairy, margins sparsely minutely serrate 25-80-toothed; petiole 1-2.9 cm. Inflorescences appearing fasciculate, 2-6-flowered, occasionally solitary, ebracteolate. Flowers pendulous, campanulate; Calyx 2-5 × 1.5-3 mm; Corolla 10-29 mm, glabrous, fused portion 7-26 mm, lobes 3-7 × 5-12 mm; stamens 12-16, 9-17 mm, filaments adnate to corolla 2-3 mm, free portion connate 1-3 mm, distinct portion 5-14 mm, glabrous abaxially, hairy adaxially; anthers 2.5-4 mm; style glabrous. Fruits drupe, ± equally 4-winged, ellipsoid to clavate, 2.4-5 × 0.7-2.6 cm.
Distribution United States Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Mississippi, North Carolina, Ohio, Oklahoma, South Carolina, Tennessee, Virginia & West Virginia. Considered naturalised in Michigan, New York, Pennsylvania & Rhode Island.
Habitat Wooded floodplains, stream banks, swamps edges, roadsides, between 0 and 1600 m asl.
USDA Hardiness Zone 5b-6a
RHS Hardiness Rating H5
Conservation status Not evaluated (NE)
Taxonomic note This species is readily distinguished from Halesia diptera in flower or fruit. Halesia carolina has 12-16 stamen and glabrous petals that are fuse almost to the tip or at the very least half their length. Halesia diptera have 7-10 stamen and hairy petals that are free to the base. The fruits of Halesia carolina have four equal sized wings and the fruits of Halesia diptera have two distinctly larger and two much smaller wings on the fruits. Our account differs from the European Garden Flora: In that account the authors recognise Halesia monticola and H. tetraptera as distinct species, but the characters used to delimit these taxa fall within the diversity of H. carolina, (Fritsch & Lucas 2000). In cultivation these morphological variants are maintained as Cultivars and Cultivar Groups.
Halesia carolina was introduced to cultivation in the UK as early as 1756 when Dr Alexander Garden, an Scottish physician who lived in Charleston, South Carolina, sent seed back to Britain. The accompanying specimens were used by John Ellis to describe the now synonymised Halesia tetraptera.
Halesia carolina is described as fully hardy in the UK but it is likely that some forms, especially from southern states and lower elevations, may not be. A good example of contrasting forms and hardiness can be seen at the Royal Botanic Garden Edinburgh. Near the East Gate entrance is a 1968 accession which is 11 m tall, this is a very freely flowering form belonging to the Halesia carolina Monticola Group, while not far from the pond is a 1939 accession, about 5 m tall, which is a shrubbier tree with branches that droop to the ground. This 1939 accession does not flower as freely and has suffered from dieback over the cold winters of 2016/17 and 2017/18. The tallest specimen in the UK of H. carolina is at Tatton Park in Cheshire, and at 22 m is as tall as specimens in its native range. Despite being a superb spring flowering tree and being in cultivation for more than 250 years, it is not a commonly cultivated outside historic plantings, large estates and botanic garden collections.
H. carolina is widely cultivated in North America, within its native range, of course, but also in the Pacific coastal states and to the north of its native range, for example at the Arnold Arboretum (Arnold Arboretum 2018). There is a 1980 record of the species having persisted in cultivation as far north as the Dominion Arboretum in Ottawa, where severe winters resulted in trees becomming multi-stemmed (Buckley 1980). It is common in continental European collections and commercially available from several sources in this area. Specimens grow, for example, at Arboretum Wespelaar in Belgium (Arboretum Wespelaar 2018), at the Tiergarten in Berlin, Germany (monumentaltrees.com 2018), and at the Kórnik Arboretum in western Poland (K. Nowak pers. comm. 2018). It is also in New Zealand collections, for example at Eastwoodhill Arboretum (Eastwoodhill Arboretum 2018).
Darke (2006) admits that it can be all but impossible to distinguish between young plants of the type and those belonging to the Monticola Group (as it is treated in Europe) however he goes on to say that while the botanical distinction may only be very slight, the gardener will note several important differences as plants mature, particularly the more spectacular floral display and the “greater architectural presence” of the Monticola Group vs. the type.
A selection introduced to cultivation by the Arnold Arboretum with light pink flowers c. 2 cm long. Darke (2006) suggests this is “probably the most reliable” of the pink-flowered forms, while also noting that the flowers are merely flushed pink. He says of this and other ‘pink-flowered’ selections that the flower colouration is better in years with cool spring temperatures.
Although becoming widely available in the nursery trade in North America this selection remains extremely rare in Europe.
Registered in 2006 from a chance seedling at Princeton Nurseries in New Jersey, this selection is reported to have a more upright, uniform habit that leads to an oval to rounded shaped tree. It appears to already be widely cultivated in the US where it is commercially available from numerous sources, though by 2018 no evidence could be found that it is yet in European cultivation.
This was raised from seed in Meehan’s nursery, German-town, Philadelphia in 1892 from H. tetraptera, now synonimised with H. carolina. It differs from ordinary H. carolina as a shrubs to 3m, shorter-stalked flowers; the corolla is more cup-shaped and leaves thicker and more coarsely wrinkled. The suggestion from previous authors was that this was a possibly a hybrid, but as H. carolina is a a cline of a single species it may well have just been natural variation.
There is no evidence of this cultivar still being extant in collections with easily accessable online databases, and does not appear in the trade in the UK or US. If it is still in existance it would be worth propagating this old and rare cultivar.
Halesia monticola (Rehder) Sargent
This cultivar group covers the diverisiy that was previously known as Halesia monticola. The plants in this cultivar group tend to be more tree like in stature, with leaves and flowers that are at the larger end of the range found in Halesia carolina.
Not a clonal selection, unlike ‘Arnold Pink’, but a name covering all other pink flowered plants of H. carolina. The colouration is variable and unstable in the species; the colour ranges from a light rose to light pink, and fades to white as the flowers age. It was reported by Spongberg (1976) that the colour pink in H. carolina is more pronounced in the shade, while Darke (2006) suggests that the colouration is improved by cool springs, or cultivation in cooler regions. The flowers also do not tend to be as large as the ‘Arnold Pink’ selection.
This clone was originally found in Ohio and was introduced to the horticultural trade via the University of Connecticut, hence the rather unusual name, although it is sometimes listed simply as ‘Wedding Bells’. The rather municipal prefix ‘UConn’ should not deter anyone from planting it, however. This cultivar is is consistently more floriferous than the type, with larger, more open flowers than many forms of H. carolina. It tends to be shrubby in habit, not exceeding 6 m in height. (Darke 2006).
A form that has creamy golden variegated margins. Darke notes that variegated forms are sometimes found “however none to date posess clear, strong variegation and they are of minor horticultural value” (Darke 2006).
Halesia monticola var. vestita Sargent
RHS Hardiness Rating: H5
Plants assigned to this group tend to be more tree like than shrubby, with a more upright habit. Their leaves are covered with a dense wooly indumentum as they break bud, becomming sparsely hairy as they mature, the base of the leaves are also more rounded compared to the type (Darke 2006). The Hillier Manual (Hillier & Coombes 2002), discussing the entity under ‘var. vestita’, suggests it produces larger flowers up to 3 cm across in gardens.
This Cultivar Group was first awarded an AGM by the RHS in 1958.