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Julian Sutton (2022)
Sutton, J. (2022), 'Magnolia × thomsoniana' from the website Trees and Shrubs Online (treesandshrubsonline.
USDA Hardiness Zone 6-9
RHS Hardiness Rating H5
Taxonomic note John Grimshaw and David Mabberley (Grimshaw & Mabberley 2022) have established that this is the correct spelling of the epithet (M. × thompsoniana has been incorectly used for nearly 200 years), reflecting both the correct spelling of the raiser’s name and its earliest publication.
This name covers all hybrids between two North American species, Magnolia virginiana and M. tripetala. They are known only from gardens, and are nowhere at all common, but deserve to be more widely grown for both foliage and flower.
The type clone, dating from early 19th century Europe, makes a rather ungainly, widely spreading shrub to 6 × 4.5 m in southeast England, even larger in milder areas. It varies between fully deciduous (losing its leaves by the end of December in colder parts of Britain) to semi-evergreen in southern North America.The leaves are elliptic, often with undulating margins, and very variable in size, to 23 cm × 10 cm. They are glossy green above, glaucous to silvery green beneath, with fine hairs across the entire undersurface. The fragrant flowers are creamy white, primrose yellow outside when in bud, held upright on leafy shoots and borne sporadically from May, but abundantly in July. They are vase-shaped,12–15 cm across, with 12 tepals, each up to 10 cm long. It thrives in a hot, sunny, sheltered site and deserves space to spread. Reports of its hardiness are rather variable. It was first noticed among seedlings of M. virginiana on Archibald Thomson’s Mile End Road Nursery in east London in 1808. Both parents were in cultivation there and early references make it clear that the seed was home-grown, despite later speculation that it apeared in wild collected seed from the United States (Grimshaw & Mabberley 2022); this was ‘the first hybrid Magnolia to be raised in the Western world’ (Treseder 1978), predating M. × soulangeana.
The suspected hybrid status of the type clone was confirmed in the 1960s when Joe McDaniel, University of Illinois, raised very similar seedlings from a controlled cross between a northern form of M. virginiana (seed parent) and M. tripetala. Even the best of these, named ‘Urbana’, had a very limited distribution and is considered a poor performer (Del Tredici 2007). Two further cultivars were chance finds in cultivation. All are sterile.
Very like the type clone; a nusery-raised plant grown as M. virginiana on a private estate in Westwood, MA, identified as this hybrid by Peter del Tredici (2007). Fully hardy in Zone 6, where the original measured 4.6 m tall with 5.2 m crown spread 13 years after planting.
Upright, broad, multi-stemmed tree. Leaves elliptic to broadly obovate, 25 × 11 cm. Selected from Olmenhof Park in Herk de Stad, Belgium by Koen Camelbeke, Jef Van Meulder and Wim Peeters before 2005.