A genus of deciduous or evergreen trees and shrubs named by Linnaeus in honour of Pierre Magnol, a professor of botany and medicine at Montpelier, who died in 1715.
The genus is most numerously represented in E. and S.E. Asia, as far south-east as Java. A little over one-quarter of the species are natives of the New World, from the N.E. United States (one species just extending into Canada) to northern South America. More than half the species are tropical; of the temperate species, almost every one has been introduced to Britain.
In one respect magnolias are the most splendid of all hardy trees, for in the size of their individual flowers they are easily first; the evergreen species, too, have some of the largest leaves of all evergreen trees hardy with us. The leaves are alternate, simple and entire, with stipules that are free from the petiole in some species, in other adnate to it. Flowers bisexual, produced singly at the end of a shoot; peduncles with one or more spathe-like bracts. Perianth of six or nine (occasionally more) segments known as ‘tepals’, arranged in whorls. In some species the tepals of the outer whorl are small and sepal-like; in describing these species it is usual to term the outer whorl a calyx and the inner segments petals, but in no species of magnolia is there a complete differentiation of the perianth into calyx and corolla. The stamens are numerous, spirally arranged to the lower part of structure (the torus), the upper part of which bears numerous free carpels, also spirally arranged. In the fruiting stage the torus is much enlarged and the carpels split on their outer side to release one or two red, scarlet, or orange seeds, each of which is attached to the carpel by a silk-like thread.
In most of the species, the bark when crushed emits a pleasant aromatic odour, and some of the American species, as well as the Chinese M. officinalis, have medicinal properties.
Perhaps no group of exotic trees gives more distinction to a garden than a comprehensive collection of magnolias. There is not one that is not worthy of cultivation, the early-flowering or Yulan section being especially noteworthy for the brilliant effect they produce in spring.
The only difficulty experienced in cultivating these trees is in establishing some of them after transplanting. The roots are thick and fleshy, and apt to decay if disturbed and lacerated when the trees themselves are at rest. Any planting, therefore, which involves root injury should be done when active growth has commenced, so that the wounds may heal and new roots be formed immediately. May is a suitable month. The more delicate-rooted species like M. sieboldii and stellata like a proportion of peat in the soil, more especially when they are young. All of them like abundant moisture and where the soil is shallow and poor, holes 18 in. deep and 2 to 4 yards in diameter should be prepared by mixing good loam, and if possible one-fourth peat and decayed leaves with the ordinary soil. The dimensions of the prepared ground should, of course, be proportionate to the vigour of the species. In most gardens the ordinary soil, well trenched and improved by adding decayed leaves, will be found suitable, but for such delightful plants as these a little extra labour and expense at the outset will be repaid.
Magnolias are propagated by seed, layering, and grafting. For the pure species, seeds no doubt are preferable, but their production in this country is uncertain, and it has to be remembered that being of an oily nature they retain their vitality but a short time if kept dry. It is advisable to sow them singly in small pots of light soil under glass. Seeds of magnolias are sometimes very long in germinating. A batch of about two hundred seeds of M. wilsonii, ripened at Kew some years ago, remained dormant after sowing for over two years, then germinated simultaneously with scarcely a failure.
Layering is a very useful means of increase and was much used by Messrs Veitch at their Coombe Wood nursery, where there were many old stools, each of which had produced hundreds of young plants. Air-layering is a possibility in gardens, when only a few plants are needed. Where layering is inconvenient or impossible, grafting will have to be employed; M. acuminata can be used as the stock for the stronger growing kinds, and M. kobus for M. stellata, M. × loebneri and other smaller growing species and hybrids. But grafting should be the last resort. Some magnolias can be propagated by cuttings, notably M. grandiflora and delavayi, both evergreen, M. stellata, salicifolia, and kobus (and their hybrids); some success has also been attained in propagating M. × soulangiana by this means.
With regard to the attitude of magnolias towards chalky soils, the late Sir Frederick Stern wrote, in his book on the garden at Highdown, near Worthing: ‘Few magnolias do well on this hot dry soil. The American magnolias, like so many of the American plants, will not tolerate lime. Some of the Asiatic species do not mind lime, such as M. delavayi, M. kobus, M. sinensis, M. wilsonii and M × highdownensis. None of the other Asiatic magnolias have ever succeeded here; perhaps the ground and the position of the garden facing south is too hot and dry for them’ (A Chalk Garden (1960), p. 44). But a wide range of magnolias is grown by Lord Rosse at Birr Castle in central Ireland, where the soil is alkaline but not chalky as it is at Highdown and is also moister (Journ. R.H.S., Vol. 78 (1953), pp. 102-104).
The standard work on the magnolias of temperate E. Asia is: G. H. Johnstone, Asiatic Magnolias in Cultivation (1955), with fourteen coloured plates, twenty half-tone figures, and one map. An older work on the whole genus, still of interest, is: J. G. Millais, Magnolias (1927). See also: Camellias and Magnolias, R.H.S. Conference Report (1950). Information on new cultivars and hybrids not included here will be found in Bud-grafted Magnolias, published periodically by Messrs. Treseder of Truro; and in the Manual of Messrs Hillier of Winchester. An account of magnolias at Kew, by S. A. Pearce, was published in Journ. R.H.S., Vol. 84 (1959), pp. 418-426; and of tree magnolias in Windsor Great Park, by T. H. Findlay, in Journ. R.H.S., Vol. 77 (1952), pp. 43-46, and Vol. 88 (1963), pp. 461-463.
From the Supplement (Vol. V)
Grootendorst, H. J. – ‘Magnolia’s en Nederland’, Dendroflora No. 18, pp. 16-40(1981).
Spongberg, Stephen A. – ‘Magnoliaceae hardy in temperate North America’, Journ. Am. Arb., Vol. 57, pp. 254-306 (1976).
[ – – ] ‘Some old and new interspecific magnolia hybrids’, Arnoldia, Vol. 36, pp. 129-45(1976).
Treseder, Neil G. – Magnolias. London, 1978. An indispensable work by a leading authority, with many line-drawings by Marjorie Blarney and forty-eight colour plates, nine from paintings by the same artist.
[ – – ] The Book of Magnolias. London, 1981. Thirty colour plates from paintings by Marjorie Blarney.
For a classification of the genus by the late J. E. Dandy of the British Museum (Natural History), see Neil Treseder’s Magnolias, pp. 25-36. This is essentially the same as the classification by the same authority published in Camellias and Magnolias (an account of the conference of 1950, published by the Royal Horticultural Society). The main nomenclatural changes made by Mr Dandy are that sect. Magnoliastrum (p. 69) is now sect. Magnolia and subgenus Pleurochasma becomes subgenus Yulania.