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The genus Pyrus occurs naturally in Europe, North Africa and Asia, and includes 10–25 species (Lu et al. 2003, Kalkman 2004). Browicz (1993) lists 38 species in his conspectus of the genus but admits that this number may be inflated, as some apparently naturally occurring species may be of hybrid origin. Pears are deciduous (rarely semi-evergreen) trees or shrubs, which may have thorns. The leaves are simple or rarely lobed, with camptodromous venation and entire or serrated margins. Stipules are caducous. Inflorescences are corymbose to racemose, with few flowers. The flowers are white or rarely pink, and 5-merous, with 15–30 stamens and a cup-shaped hypanthium. The fruit is a pyriform (pear-shaped) or globose pome with brown to yellow skin, persistent to caducous sepals, and a membranous or cartilaginous core. The flesh is rich in stone cells (sclereids), giving it a gritty texture (Lu et al. 2003, Kalkman 2004).
In the trio of ‘fruit trees’ that also contains Malus and Prunus, Pyrus is somewhat the poor relation in ornamental representatives, perhaps because they lack floral brilliance compared to the others. The pears have other charms, however, particularly in their autumn coloration, and they can make excellent long-lived landscape trees. Culinary pears aside, there are comparatively few selected cultivars. Most are American selections of P. calleryana, raised to replace the over-planted, brittle-wooded ‘Bradford’ – ‘one of the great widget trees of American commerce’ (Dirr 1998) (whatever that means). Of the numerous cultivars available in North America (see Jacobson 1996, Dirr 1998), though often not in Europe, the fastigiate ‘Chanticleer’ is generally considered to be the best; but again there is danger of this being planted too often. It is interesting to reflect that P. calleryana was first introduced by the US Department of Agriculture for investigation as a potential rootstock for cultivated pears.
Pyrus are generally very hardy, and will grow in any good soil, the smaller species often tolerating rather dry sites. Fireblight can be a problem where this disease is prevalent, and the usual treatments apply. Propagation is by seed or grafting. The genus is usually well represented in arboreta, but particularly good collections may be found in the Morton Arboretum and at the Sir Harold Hillier Gardens. In the United States, the National Clonal Germplasm Repository at Corvallis, Oregon holds a magnificent collection of interesting edible (or potentially edible) plants, including many accessions of obscure Pyrus taxa – and as part of the US National Plant Germplasm System, has an admirable policy of freely distributing material on request.
Deciduous trees, rarely shrubs, with simple, toothed, but seldom lobed leaves and top-shaped or globose fruits rarely indented at the junction with the stalk, grit-cells abundant; styles two to five, free; stamens twenty to thirty.
The true pears include some of the tallest and bulkiest trees in its group of genera, but the species as a whole have not such striking attributes for the garden as some of the other sections. Their flowers are often beautiful, but they have little attractive colouring in fruit, and the leaves frequently die off black. Some, like P. salicifolia and P. nivalis, are particularly effective in their young expanding foliage, being covered with a snowy-white, thick down. The pears, although represented in N.E. Asia, are more particularly identified with Europe – especially S. and E. Europe – Asia Minor, and N. Africa. No species is a genuine native of the New World. Seeds ripen freely, but owing to the hybrid origin of some it is safer to graft the various sorts on their own or nearly allied seedlings – especially as many cultivated trees are of selected forms that could not be relied on to come true from seed.