This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
There are about thirty species of Juniper known, mostly ornamental and easily grown in moist soil. They are increased by seeds and cuttings, and choice varieties are grafted on stocks of the common species. J. chinensis is dioecious, and one of the best with pyramidal habit, the male plant being better than the female. There are several varieties, such as albo-variegata, with silvery variegation at the tips of the shoots; aurea, with beautiful golden young foliage; and glauca, with blue-green tints. The Common Juniper (J. communis) grows from 3-50 ft. high, and has also several varieties, of which the Irish Juniper (kibemica), with erect columnar habit, is one of the best. Other forms are alpina, glauca, and pendula. The Common Savin (J. Sabina) is a nice branching shrub up to 8 ft. high, with several varieties, including prostrata, a good trailing plant for rock gardens; tamariscifolia, the "Carpet Juniper", a trailer with bright-green slender shoots; and variegata, the branchlets of which are prettily variegated with creamy white or pale yellow. The Red or Pencil Cedar (J. virginiana) grows up to 90 ft. in the United States, but is often only a low shrub in some places. There are several varieties, such as albo-variegata, aureo-variegata, pendula, Gossaintheana, elegans, glauca (very handsome), and several others. The greenhouse Juniper is dealt with in Vol. II, p. 177.