Magnolia × thomsoniana de Vos

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Credits

Julian Sutton (2022)

Recommended citation
Sutton, J. (2022), 'Magnolia × thomsoniana' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/magnolia/magnolia-x-thomsoniana/). Accessed 2022-06-27.

Genus

Synonyms

  • Magnolia × thompsoniana orthog. var.

Other taxa in genus

Glossary

bud
Immature shoot protected by scales that develops into leaves and/or flowers.
clone
Organism arising via vegetative or asexual reproduction.
entire
With an unbroken margin.
glaucous
Grey-blue often from superficial layer of wax (bloom).
hybrid
Plant originating from the cross-fertilisation of genetically distinct individuals (e.g. two species or two subspecies).

Credits

Julian Sutton (2022)

Recommended citation
Sutton, J. (2022), 'Magnolia × thomsoniana' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/magnolia/magnolia-x-thomsoniana/). Accessed 2022-06-27.

USDA Hardiness Zone 6-9

RHS Hardiness Rating H5

Taxonomic note David Mabberley and John Grimshaw (pers. comm. 2021) have established that this is the correct spelling of the epithet (M. × thompsoniana is more usually seen), reflecting both the correct spelling of the raiser’s name and the earliest usage; formal publication of this research will follow.

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 London nursery in 1808. Whether these were from Thomson’s own seed (he seems to have grown both parent species) or from an imported seed batch is a moot point: it is certainly possible to claim that 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.


'Cairn Croft'

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.


'Olmenhof'

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.