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Article from Bean's Trees and Shrubs Hardy in the British Isles
Article from New Trees by John Grimshaw & Ross Bayton
'Torreya' from the website Trees and Shrubs Online (treesandshrubsonline.
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The five species of Torreya occur in China (T. grandis, T. jackii), Japan (T. nucifera) and the United States (T. californica, T. taxifolia). They are dioecious (rarely monoecious) evergreen trees and shrubs with distinctive large plum-like ‘fruits’. The branches are in whorls; branchlets nearly opposite or whorled. Leaf arrangement is decussate or opposite, two-ranked; the leaves are green, leathery, linear to lanceolate, the apex sharply acuminate, the base twisted, the lower surface with two distinct whitish bands of stomata. Male (pollen) cones are axillary, solitary, short-pedunculate, with four to eight whorls of four microsporophylls. The seed-bearing structures (cf. cones) are axillary and sessile, each bearing two pairs of decussate bracts. There are two ovules per structure, though one usually aborts. The surviving ovule develops into a drupe-like fruit, with the woody seed completely enclosed within a fleshy aril; the seed matures in the autumn of the second year (Hils 1993, Fu et al. 1999d).
Torreya is an interesting and not unattractive genus whose members can form tall, single-stemmed trees, but are often seen as somewhat scruffy bushes of no particular merit. The large, green plum-shaped fruits are a surprising feature in autumn. The most widely tolerant seems to be T. californica, which is growable across large areas of maritime northern Europe and the Pacific Northwest. It does well throughout much of southern Britain, flourishing and even self-sowing in the cool dry limestone conditions of Colesbourne, Gloucestershire. The only other species that is regularly collected and relatively frequently planted is T. nucifera, which seems to require a hot and preferably humid summer to perform at its best – for example, in the eastern United States – although there are a few reasonable specimens in Europe. It is said to require an acidic soil (Huxley et al. 1992). In addition to the taxa described below, T. jackii, from northern Fujian, northeastern Jiangxi and southern Zhejiang, has been in cultivation in the United States since 1994, when cuttings were collected from a tree in Nanjing Botanic Garden by a NACPEC expedition to Wudang Shan. It is grown by the Arnold Arboretum and the US National Arboretum, with material under glass and (at the latter institution at least) outdoors (R. Olsen, pers. comm. 2008). The Chinese taxa are surprisingly poorly known in western horticulture, and more material is needed.
Propagation of Torreya is from seed, which can take two winters to germinate, or from cuttings as for Taxus, but plants from cuttings may not form monopodial trees.
A genus of four or five species of evergreen trees, named in honour of Dr John Torrey, a famous American botanist. It is allied to Taxus. The branchlets are opposite and the linear, firm, sharp-pointed leaves are terminated by a fine hard point and are arranged in opposite spreading ranks. Flowers unisexual, the sexes either on the same or separate trees (solitary examples have borne fertile seed in this country). The male flowers are solitary in the leaf-axils and are composed of six to eight whorls of stamens. Fruit egg-shaped, consisting of a large bony seed enclosed entirely in a tough, fleshy coating.
Although not closely related, and placed in different families, there is a similarity in foliage between Torreya and Cephalotaxus. A difference can, however, be found in the undersides of the leaves: in Torreya the stomata are confined to two narrow longitudinal shallow grooves, while in Cephalotaxus the stomata are arranged in numerous lines, which occupy the greater part of the undersurface of the leaf.
Two species are American, and of these T. californica is the most widely planted and successful species in Britain; the other, T. taxifolia Arn. of Florida, is very rare in cultivation and unlikely to thrive in our climate. It is also very rare in the wild.
The torreyas are usually raised from imported seed, which quickly deteriorates; or by grafting on the common yew. Cuttings can be struck, but plants raised this way are said to grow poorly.