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A deciduous, very spiny shrub or small tree 8 to 20 ft high, often as much wide, with smooth, green, crooked, angular branchlets. The spines are from 1 to 2 in. long, very stiff, straight, and sharply pointed. Leaves of three, sometimes five leaflets, which are obovate, the middle one 11⁄2 to 2 in. long, the side ones half as large; leaf-stalk winged. Flowers sweetly scented, produced from the axils of the spines before the leaves, pure white, 11⁄2 to 2 in. across, with four or five concave obovate petals. Stamens pink, not united. Fruit like a small orange in colour and shape, about 11⁄2 in. across, covered with down.
Native of Korea and N. China. This species is one of the most striking of hardy Chinese plants. It is hardy at Kew, having survived 30° of frost without injury; and although it does not often ripen fruit there, it flowers regularly during May every year. Its foliage is often scanty, but that enables its formidable armature to be the better seen. Were it common enough, it would make a good hedge plant: there is a hedge in the Public Garden of Milan 100 yds long, which, when I saw it, was only 3 ft high, too small for so vigorous a shrub as this, but which shows that it stands clipping well. In the western counties it fruits freely, and in the Vicarage garden at Bitton, near Bristol, there is a tree that has borne fruit for many years past. It is a plant every garden should contain for its beauty and distinction, its perfect hardiness, and its interest as a very close ally of the lemon and orange. The fruits are too bitter and acrid to be eaten raw, but they have been made into a conserve by boiling in sugar. It should be given a sunny position and a deep, moderately rich, soil. English ripened fruits produce good seed, from which I have raised young plants. It is also said that cuttings of half-ripened wood put in a close frame will take root.
Hybrids between P. trifoliata and the orange were made by W. J. Swingle at Eustis, Florida, in 1897. Eleven were named in 1905, and a description of the more important clones will be found in Bailey’s Standard Cyclopaedia of Horticulture under the heading ‘Citrange’. The cross was also made in France in 1894 by Armand Bernard, and one of these hybrids, named after the raiser, was described and figured in Revue Horticole, also in 1905 (p. 244).The citranges are hardy in southern England, but are most likely to flower and fruit if planted against a sunny wall. Although many of the Swingle hybrids were introduced to this country, they have never been much grown, possibly because they are no more ornamental, and less reliable in their flowering and fruiting, than P. trifoliata. An example of a citrange can be seen by the south entrance to the Temperate House at Kew.