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There are 11 species of Nyssa, four in North and Central America and seven in eastern and southeastern Asia (Andrews 2001). They exemplify the classical eastern Asia/North America biogeographical pattern (Wen & Stuessy 1993). Nyssa species are small to medium-sized, deciduous (or evergreen) trees and are often characteristic of wet and flooded forests. The bark is grey and deeply furrowed; emergent root arches may be formed when the tree grows in water. The leaves are simple, elliptic or ovate and alternate; they may be membranous or leathery, and produce a range of autumn colours. Typically, they are clustered at the branch tips. All Nyssa species are dioecious, with single flowers or inflorescences in an axillary position. Staminate flowers are produced in heads or racemes and are typically 5-merous. Pistillate flowers (rarely, bisexual flowers occur) are solitary or in heads of two to four; they are (4–)5-merous with an urn-like tubular corolla. The fruit is an ovoid or elliptical drupe with a fleshy mesocarp and a woody endocarp. Fruits are red, purple or blue-black, and the endocarp has several conspicuous longitudinal ridges or papery wings (Andrews 2001, Qin & Chamlong 2007). The genus has been comprehensively reviewed from a horticultural viewpoint by Susyn Andrews (2001).
The name Nyssa is always likely to conjure up the picture of a flaming specimen of N. sylvatica lighting up the autumn landscape. This is a classic garden tree, with numerous selected cultivars, though requiring moisture, acidic soil and warm summers to perform at its best. Its qualities give its relatives an interest that they might perhaps not otherwise excite, especially in cooler areas. Of the other members of the genus, N. sinensis seems to be the next best bet for our area, colouring brilliantly in autumn, but although it tolerates cooler climates somewhat better than N. sylvatica (C. Howick, reported in Andrews 2001) it only forms a good tree in warmer parts. Nyssa is a typical example of a genus from places with stickily hot summers with one member that tolerates less torrid climes, the rest, however, always pining for the heat. The danger of relying on USDA Hardiness Zones as a guide to ‘growability’ is also shown particularly clearly in this case. Even the southeastern N. ogeche can be rated in Zones 7–9 in terms of the winter temperatures it can tolerate – but without its full measure of summer heat it will fail to prosper.
Propagation is by seed, which requires a cool stratification period (Dirr 1998). Cultivars of N. sylvatica can be grafted, but cuttings are generally not very successful. Seedlings should be planted out young, as they develop a tap root and resent disturbance (Dirr 1998, Hudson 2004).
A genus of about ten species in eastern N. America, N. Mexico, the Himalaya, and western Malaysia, of which only N. sylvatica is commonly grown in the British Isles. Leaves alternate, without stipules. Flowers small, unisexual, both sexes often occurring on the same tree. Male flowers numerous, in slender-stalked heads or racemes, females in fewer-flowered clusters, or solitary. Fruit a drupe, with a one-seeded stone. The family Nyssaceae is allied to the Cornaceae, in which Nyssa was once placed.
Propagation is by seeds or by layers. The nyssas transplant badly and should be given a permanent place as early as possible.