A group of about forty species generally known as ‘silver firs’. They are found in Europe, N. Africa, temperate Asia and on the American continent from Canada to Guatemala. They are mostly conical and very symmetrical in form, especially when young, and the finest are from 200 to 300 ft high. They produce their branches in whorls or tiers, one tier yearly. Leaves always linear or nearly so, from 1⁄20 to 1⁄8 in. wide, with invariably two bands of stomata beneath, occasionally lines of stomata above also; they are always attached to the shoot in a spiral arrangement, but by a twisting at the base are usually made to appear in two opposite sets, the green faces of all uppermost. Female cones always erect, in which respect they differ from those of Picea (the spruces), and from Tsuga (the hemlocks), both of which genera have been, and still are, often called “Abies”. There is a simple way of distinguishing a fir (Abies) from a spruce by pulling off a living leaf from the shoots: in the firs the leaf breaks off sharply at the base where it joins the twig, but in the spruces (Picea) it tears away a little of the bark with it. Also, the leaves of the spruces are inserted on woody, peg-like projections which persist on the stems for many years after the leaves have fallen.
The cones are built up of a close spiral arrangement of overlapping, usually more or less fan-shaped scales, to the outer surface of which a bract is always attached. The length of this bract and whether or not it protrudes beyond the scale, affords a good distinguishing character between the species. Seeds are borne in pairs on the inner side of the scales, and are winged. The male flowers occur on branches separate from the females, and are borne on the under side of the branch; anthers highly coloured. On flowering and cone-bearing branches the leaves frequently alter much in character, becoming shorter, stiffer, sharper pointed, and more erect.
The silver firs are undoubtedly best suited in a moist climate where late spring frosts are rare. Nowhere in the British Isles, perhaps, do they, as a whole, succeed quite so well as in the Perthshire valleys. Where the rainfall is deficient, lack of moisture can to some extent be compensated for by a good deep soil. Whenever possible they should be raised from seeds, but of some sorts cuttings may be made to take root. The cuttings should always be taken from leading shoots, as distinct from lateral ones, which rarely develop a good leader. The best plan is to head back a plant, thus inducing it to make several shoots; these are then taken off with a slight heel of old wood attached, and placed singly in small pots of sandy soil in a gentle bottom heat. But both cuttings and grafts should only be resorted to when seeds are unobtainable. Several species, among them alba, amabilis, magnifica, nordmanniana, and procera, are subject in many places to attacks by aphides of the genus Adelges; gouty swellings on the branches and woolly patches on branches and trunk are a sign of their presence. The remedy, only practicable on young trees, is regular spraying with an emulsion of paraffin and soft soap or some modern aphicide.
From the Supplement (Vol. V)
The most important work on the genus is: T.-S. Liu, A Monograph of the genus Abies (1971), published by the Department of Forestry of the National Taiwan University, Taipei, Taiwan, with detailed botanical illustrations and distribution maps for each species. The silver firs cultivated in the British Isles are surveyed by John Horsman in The Plantsman, Vol. 6, pp. 65-100 (1984), with notes on availability in commerce.
Keith Rushforth’s contributions to the taxonomy of the Chinese species of Abies, published in Notes from the Royal Botanic Garden, Edinburgh, in 1984-5, are referred to below under A. chengii, A. chensiensis, A. fabri, and A. fargesii. The editor is also indebted to him for informative letters on taxonomic problems concerning A. delavayi and A. forrestii.