Read about Pyrus in the Standard Cyclopedia of Horticulture
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Pyrus (Latin name of pear tree). Sometimes spelled Pirus. Rosaceae. The Pome-fruits, as all the kinds of pears, apples, and crab-apples; also many small trees and bushes grown for the very handsome early flowers and sometimes for the attractive habit, foliage, and little fruits. Woody plants, bearing mostly on spurs, with simple but sometimes lobed alternate lvs. (pinnatifid sometimes in P. heterophylla): fls. usually perfect, but rarely polygamous, regular, in spring; torus urn-shaped and attached to the carpels and finally closing over them,and with them becoming fleshy in fr.; calyx-lobes 5 and persistent upon the top of the young fr., or in some cases falling away at maturity or before; petals 5, white or red, perigynous; stamens 15-20 or more; styles 2-5, crowning a 2-5-loculed inferior ovary in which the locules are usually 2-seeded. (Figs. 3266, 3267). Pyrus is a polymorphous genus, in the northern hemisphere. The species are mostly small trees, bearing clusters of showy white or blush fls. with the lvs. or in advance of them. They are natives mostly of cool temperate regions, and the greater part of them are hardy in the northern United States. There are widely unlike practices among botanists in defining this important and interesting genus. Half a century ago, when it was a widely prevalent practice to assemble groups which agree in general gross structure and which can be held together by a broad definition, Pyrus was held to include not only the pears and apples, but the mountain-ashes or sorbuses, the medlar and quinces, the chokeberries and other groups (Bentham & Hooker, Genera Plantarum, 1867). As late as 1894, Focke (Engler & Prantl, Pflanzenfamilien) holds Pyrus intact except for the separation of Cydonia and Mespilus. While many botanists still hold most or all of these groups in Pyrus, the present tendency to segregate all groups for which separate definitions can be found results in the dismemberment of Pyrus. As the old rather gross assemblage, resulting from the effort to find agreements, can hardly be expected to hold, so the present disunion, resulting from the effort to find differences, may be expected to pass, and the practicable and convenient grouping may be found somewhere between the two extremes. There seems to be good justification for the separation of Cydonia and Mespilus, and perhaps also for Sorbus and Aronia, but it is yet to be determined whether the separation of Malus (the apples) will meet with continuing favor. See Malus, p. 1973, Vol. IV. The many-seeded carpels of Chaenomeles (Figs. 3268, 3269) and Cydonia and the absence of fr.-stalk (Fig. 3270) afford good structural characters, as well as the fl.-bearing habit and other characters. Many of the species that have been named under Pyrus will be found in Sorbus. If the genus is held to comprise the pears and apples and no others (Pyrophorum and Malus), there are probably fifty or sixty species. The aronias, by some kept as a distinct genus (page 396, Vol. I.), comprise a small group of North American bushes with white flowers in corymbs and attractive little fruits. Under Pyrus, the names are P. arbutifolia, Linn., the red chokeberry; P. atropurpurea, Bailey, the purple chokeberry, sometimes regarded as a variety of the former; P. melanocarpa, Willd., the black chokeberry; P. floribunda, Lindl. (not Hort.), of garden origin. The fruit of Pyrus is of the kind known to botanists as a pome. The morphology of the pome is still perhaps a subject of disagreement, although most botanists now consider it to be a hollow torus (receptacle), or hypanthium, or cupula, in which the ovary is imbedded. Fig. 3271 illustrates the theoretical structure. The ovary is at b, wholly inclosed in the fleshy torus a. Most of the edible part of the apple or pear, therefore, is considered to be torus, whereas the core is ovary. This ovary, in common apples and pears, is of five carpels or cells, as shown in the cross-section (Fig. 3272). It was formerly held that the edible part is largely calyx-tube, but various morphological considerations have inclined students to regard it as stem rather than calyx; the term calyx-tube is still retained, however, in descriptive writings. One of these considerations is the fact that apples sometimes bear a rudimentary leaf (as in Fig. 3273), an organ which is commonly borne only by stems. Apples sometimes take on most unusual and grotesque shapes, and two or more fruits may coalesce into one. Some of these forms, from an orchard of Pearmains, are shown in Fig. 3274. These malformations may be due in part to insufficient pollination, although such teratologies are yet to be well explained. Aside from the pomological pears and apples, the genus Pyrus as here defined includes many very attractive small trees and shrubs. The outlying pear species are not much grown, although well worth cultivation for interesting foliage and for good white spring bloom. P. salicifolia, P. elaeagrifolia, and P. betulaefolia are among the best of these, and the only ones that are likely to appear in collections. The silvery foliage of the first two is attractive. They are hardy in the northern states and probably in Ontario. It is among the crab-apples, however, particulary of the Asiatic species, that the most ornamental plants are to be found. Some of them, as P. pulcherrima (P. floribunda) and P. Halliana, have long been popular, but several others are fully as good and it is possible to secure considerable variety. All the species included in the numbers 21 to 36 in this account are probably hardy in parts of New York state and some of them can be grown in Canada. P. baccata is hardier even than the common apple tree, and is therefore sometimes used for stocks and as a parent in hybridizing. All these crabs may be raised as seedlings, for they bloom profusely when only a few years old, or they may be grafted on any of the related stocks. The Asiatic crabs are profuse bloomers, and the pink-and-white effect of blossoms and buds as the leaves are unfolding or just preceding the leafage constitutes one of the most charming prospects in the spring plantation. Some of them hold their small berry-like fruits well into the winter, or even to spring, affording a continuing interest. They are of the easiest culture in well-drained soil. All the species are probably subject to scale, and they should be well sprayed. Particularly to be recommended for the central and northern states east of the Great Lakes are P. pulcherrima, P. Halliana, P. Scheideckeri, P. Sieboldii, P. prunifolia var. Rinki, and P. Sargentii, the last a bush with pure white flowers. The native American crabs, described in numbers 37 to 45 in this list, are yet little known to planters, but they comprise much promising material, and they should yield horticultural subjects for the entire area of the United States, outside the semi-tropical regions, and for good parts of Canada. As a class they bloom later than the Asiatic species. As yet, only P. ioensis appears to have yielded a good double-flowered form. With the recent botanical discrimination in this interesting group, attention will probably be called to a closer study of the forms by collectors. They are easy of culture, and may be readily increased by grafting. Hybridizing will probably play an important part in the horticultural development of the ornamental crabs, as they cross freely. It is probably due to this cause that the Asiatic forms are so difficult to distinguish botanically. The pears and apples appear not to intercross, although the curious P. auricularis is generally considered to be a hybrid between the pear and the beam-tree (Sorbus Aria). The pear may be made to grow for a time when grafted on the apple, but it is usually impossible to graft the pear species permanently on the apple species with any degree of success; yet pears thrive on quinces and also on hawthorns, which are well-marked genera. In nursery practice when pear stocks are not at hand, long pear cions may be worked on apple pieces and roots may form from the cion and the pear become own-rooted on the failure of the apple stock. Apples appear not to be successful on pears.
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Read about Pyrus in the Standard Cyclopedia of Horticulture
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References
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
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