The junipers are spread widely over the temperate and subtropical regions of the northern hemisphere, the hardy species coming from China and Japan, N. America, Europe, and N. Africa. The only species native of the British Isles is J. communis, which is not uncommon on chalk hills. They are evergreen, and range from trees up to 100 ft high down to low, spreading, or prostrate shrubs. The bark is usually thin, and often peels off in long strips. Leaves of two types: (1) awl-shaped, and from 1⁄2 to 7⁄8 in. long, borne in whorls of threes or in pairs; (2) small, scale-like, and rarely more than 1⁄16 in. long, arranged oppositely in pairs and closely appressed to the branchlet. The first kind is found on the juvenile plants of all species; and several species, notably those of the communis group, retain it permanently. But other species, namely, those of the Sabina section, including J. virginiana and chinensis, as they get older develop more and more of the minute scale-like type of leaf which is essentially characteristic of the adult plant. A number of species, long after they have reached the fruit-bearing stage, continue to produce the juvenile as well as the adult type. This peculiarity is, however, apparently more characteristic of cultivated than of wild specimens. The flowers are unisexual, and most frequently the two sexes occur on separate trees, sometimes on one. The male flowers are small, erect, columnar or egg-shaped bodies, composed of ovate or shield-like scales, overlapping each other and each carrying anthers at the base. The fruit is composed of usually three to six coalescent, fleshy scales, forming a ‘berry’ that carries one to six seeds. It is this fruit that distinguishes the scale-leaved junipers from Cupressus, which they much resemble in foliage. Without fruit, the junipers can usually be recognised by a peculiar, aromatic, somewhat pungent odour, especially strongly developed in the savin.
Junipers like a well-drained soil, and most of them are lime-tolerant. This gives the genus a special value in chalky districts, where the impossibility of growing satisfactorily most of the heath family somewhat limits the number of evergreens available. Many of the species take two years to ripen their fruit, and the seeds will often lie dormant a year. Their germination may sometimes be hastened by plunging them in boiling water from three to six seconds, but this should only be regarded as an experiment, and tried with a portion of the seeds. All junipers can be increased by cuttings, a method especially suitable for the shrubby sorts.
From the Supplement (Vol. V)
A very useful assessment of the many junipers of low, spreading habit, based on trials held at Boskoop, will be found in Dendroflora No. 21 (1984), pp. 3-38, with an English summary. On p. 34 there is a list of cultivars which are not recommended (left-hand column) and of those by which they have been superseded (right-hand column).