In the garden at Santa Cruz, California, Drury Todd Gresham (d. 1969) raised altogether some three thousand hybrid seedlings, involving M. × soulangeana and most of the species and varieties of the Yulania group. But it is reasonable to restrict the term ‘Gresham Hybrids’ to the two related crosses for which he is best known. The pollen-parent for both was M. × veitchii (M. heptapeta × M. campbellii). The seed-parents were:
Group 1 M. quinquepeta, probably ‘Nigra’.
Group 2 M. × soulangeana ‘Lennei Alba’.
The crosses were made in 1955 and, remarkably, one seedling flowered in the autumn of 1960. The history of Mr Gresham’s experiment, with descriptions of the seedlings that had flowered by 1962, will be found in the article by him published in the Morris Arboretum Bulletin, Vol. 12 (1962), reprinted with some additional material in Journ. R.H.S., Vol. 89, pp. 327-32 (1964).
It will be seen from the parentage that only three species are involved in the crosses – M. heptapeta and M. quinquepeta (the two parents of M. × soulangeana) and M. campbellii. Further, that Group 2 come near to being back-crosses, ‘Lennei Alba’ being near to M. heptapeta, one of the parents of M. × veitchii.
Scions of some Gresham hybrids reached Britain late in the 1960s and included some named after the publication of the raiser’s article. The oldest set grows in the Hillier Arboretum, Ampfield, Hampshire, and we are indebted to the Curator, Mr J. M. Gardiner, for notes on some of these. In 1974 the Trials Station for Woody Plants at Boskoop obtained a set from Messrs Hillier and the most successful were described by the late Herman J. Grootendorst in Dendroflora No. 18, pp. 36-7 (1981).
The following seem to be the most promising. The heights given are those attained by the plants in the Hillier Arboretum (1986).
’Heaven Scent’ (Group 1). – A very vigorous spreading shrub with dark green leaves. Tepals spreading-erect in the open flower, nine, about 4 in. long, shortly and abruptly pointed at the apex, uniform rose on the outside when opening later fading but retaining a median line of pink, which is deepest at the base. Very free-flowering. 19 ft.
’Manchu Fan’ (Group 2). – A medium-sized tree with large, almost pure white flowers. This is similar to ‘Sayonara’ but the flowers open more widely. 13 ft.
’Peppermint Stick’ (Group 1). – A large shrub of slender habit. Flowers narrow-cylindric in the bud stage, whence the name. Tepals pure white except for a flush of pale purple at the base and a line of the same colour on the back, up to 6 in. long, the outermost whorl reflexed, the inner upright. 19 ft.
’Royal Crown’ (Group 1). – Flowers almost 12 in. wide when fully expanded. Tepals nine to twelve, slightly inrolled, dark wine-red on the outside, white inside. This is proving slightly tender.
’Sayonara’ (Group 2). – Flowers globular, with broad tepals, which are white, with a pink flush at the base, about 4 in. long. This, like ‘Manchu Fan’, will make a tree, but is reported to have brittle branches. It flowers well in the Hillier Arboretum. 13 ft.
Others that have been introduced, all described in Mr Gresham’s article, are ‘Raspberry Ice’ (Group 1), ‘Rouged Alabaster’ (Group 2), and ‘Vin Rouge’ (Group 1).