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.
Two species, T. gigantea (T. Lobbi) and T. occidentalis, the American Arbor Vita3, and their varieties, are chiefly grown. T. gigantea is a fine pyramidal tree, quick in growth and excellent for making hedges. There are several varieties, such as atrovirens, aurea, lutea, gracilis, etc. T. occidentalis grows naturally in cold wet swamps and on rocky banks. There are many forms, including compacta, alba, aurea, argentea, lutea, Ellwangeriana, dense growing; Hoveyi, roundish and compact; Vervoeneana, slender and golden tinted; and others.
T. (Biota) orientalis, from China, is somewhat variable in habit, and has many pretty varieties having silver, gold, blue-green, and variegated foliage (argentea, aurea, glauca, variegata), and others differing in habit, such as compacta, gracilis, elegantissima, pyramidalis, etc The Weeping Arbor Vitae, pendula, has drooping thread-like branchlets.
T. dolabrata (better known as Thujopsis) is a fine Japanese tree, with drooping flattened branches. The variety loetevirens is a dense-growing bush, 4-6 ft. high, excellent for hedge purposes; and the variety variegata has pale-yellowish branchlets.