In order to gain a broader perspective on Fraser fir, it is important to understand the relationship among the all the fir naturally occurring in the Appalachians.
Fraser fir (Abies fraseri (Pursh) Poir.) occurs in limited disjunct mountain-top populations primarily in North Carolina but also in south Virginia and eastern Tennessee. Balsam fir (Abies balsamea (L.) Mill.) occurs extensively in Canada and the northeastern United States. Fraser fir and balsam fir are closely related species. The most conspicuous trait that distinguishes Fraser from balsam fir is the relative length on the cone scales and bracts. In Fraser fir the bracts are much longer than the cone scales and curved downward whereas in balsam fir the bracts are much shorter than and are fully enclosed within the cone scales (3,4,5).
Several isolated populations of balsam fir located in West Virginia and the Shenandoah National Park in northern Virginia have cones in which the relative length of bract to scale is intermediate between Fraser and balsam fir. Fir from these populations are called intermediate or bracted balsam fir and have been designated as a variety of balsam fir (Abies balsamea var. phanerolepis Fern.) (3,4,5). Fir from Canaan Valley, West Virginia, which is currently receiving considerable attention in the Christmas tree industry is of this intermediate variety.
Variation studies of morphological, anatomical and chemical characteristics have shown that Fraser, intermediate and balsam fir are all part of a cline or gradual variation pattern. Not only do bract lengths decrease and cone scale lengths increase from south to north but a host of other traits also change along this geographic gradient (3,4,5,6).
Based on variation patterns and fossil evidence, fir forests are believed have existed in one continuous population from Canada southward as far as coastal Georgia, Alabama and Florida during the glacial advances of the Pleistocene Era. As the climate warmed after the Ice Ages, firs at lower elevations in southern latitudes were replace by better adapted species (5,6). Thus, Fraser fir is the southern remnant of a once continuous fir population. In fact, some taxonomists consider Fraser fir to be another variety of balsam fir rather than a separate species (5).
These relationships are important to remember. Under some circumstances, substituting intermediate fir (Canaan fir) or balsam fir from southern populations for Fraser fir may be a feasible option for North Carolina Christmas tree growers. Further, Fraser, intermediate and balsam firs, can readily be inter-crossed using control-pollination techniques although they do not naturally hybridize due to geographic isolation (1,2). Hybrids between Fraser and intermediate or true balsam fir may possess desirable characteristics of both parental species. By back-crossing hybrids to Fraser fir for several generations it may be feasible to move any desirable genes from the extensive balsam fir gene pool into the more restricted Fraser fir gene pool.
Literature CitedHawley, G.J. and D.H. DeHayes. 1985. Hybridization among several North American firs. II. Hybrid verification. Can. J. For. Res. 15:50-55.
Robinson, J.F. and E. Thor. 1969. Natural variation in Abies of the southern Appalachians. Forest Science 3:238-245.
Thor, E. 1968. Research with native Abies in the southern Appalachians. Am. Christmas Tree Journal. 12(4):29-33.
Thor, E. And P.E. Barnett. 1974. Taxonomy of Abies in the southern Appalachians: variation in balsam monoterpenes and wood properties. Forest Science 20:32-40.
Reprinted from Limbs & Needles with permission.