Each species is described in terms of its trade and other common names, distribution, tree characteristics, and wood characteristics. Wood characteristics include weight (plus moisture content [MC] and specific gravity [SG]), mechanical properties, drying and shrinkage, work­ing properties, durability, preservation, toxicity, and uses. Finally, additional sources of information are cited.

Other Common Names: The scientific name is followed by one or more trade names or common names. The most generally used common name (trade name) is in bold face. These names were taken from our database of common names and our work in conjunction with the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia. While this database is vast (over 160,000 names), it will never be complete, as new common names appear constantly.

Distribution: Information on native or introduced growth ranges is noted.

The Tree: Tree form and size are described.

General Wood Characteristics: This section describes the appearance of wood of individual species and species groupings: sapwood and heartwood colorations and unusual changes on exposure to light or air. If anatomical elements are large and irregular, the wood is described as having coarse and uneven texture. If these same features are small and evenly distributed, the texture is fine and uniform. Grain defines the arrangement or alignment of wood tissue—straight, spiral, or interlocked. Distinctive scents and tastes are noted. Woods with gummy, oily, or resinous exudates are indicated.

Weight: Specific gravity or density may be related to important wood attributes such as mechanical strength, shrinkage, paper-forming properties, and cutting forces required in machining. In assessing the use potential of a species, specific gravity often receives first attention.

Basic specific gravity (noted as green values in tables) is the ratio of wood density to the density of water at 39oF (4oC) and is calculated from the ovendry weight and volume in the green condition. This may range from less than 0.34 for balsam poplar, Populus balsamif­era, to about 0.88 for live oak, Quercus virginiana. Density calculated from weight and volume when the woods are green or when air dry, usually at a moisture content of 12 per­cent, is also given. This value may range from about 20 to 55 lb/ft3 or 320 to 881 kg/m3.

Mechanical Properties: It must be emphasized that the mechanical properties presented here by species are taken from various sources. Sampling and testing procedures may have varied considerably. Values are given so that species can be compared and selected for targeted end-uses. However, the data reported may not be acceptable to regulatory bodies as a basis for assigning design properties. Such interests are beyond the scope and intent of this document. Sources from which the strength data were obtained are referenced by numbers in parentheses and listed in the Additional Reading and References Cited sections.

Data are given for strength tests on wood in the green and dry conditions. The properties include bending strength (modulus of rupture [MOR]), stiffness in bending (modulus of elas­ticity [MOE]), compression parallel to the grain (maximum crushing strength [C| | ]), com­pression perpendicular to the grain (stress at proportional limit [C⊥]), work to maximum load (WML), hardness, and shear parallel to the grain (shear | | ). Most test results reported here are based on the ASTM D 143 procedures using 2-inch (50.8-mm) specimens, except where noted.

Drying and Shrinkage: The response of individual woods to air-drying and kiln-drying is noted as well as the absence or presence of degrade due to checking, warp, or collapse. Per­centage of shrinkage values (volumetric, radial, tangential) from the green to ovendry condi­tion (0 percent moisture content) or green to various air-dry conditions (6, 12 or 20 percent moisture content) are given. If no kiln schedules were found in the literature, none is recommended.

Working Properties: Much of the information given on working properties of individual species is highly subjective. Described are ease of working with hand and machine tools, tendencies to torn or chipped grain, smoothness of finish, dulling by cutters, and ease of veneering. Nailing, screwing, or gluing characteristics may be included as well as steam- bending properties if well suited for these purposes.

 

Durability: Resistance of the wood to attack by decay fungi, insects, and marine borers is described. Wood kept constantly dry does not decay. Further, if it is kept continuously sub­merged in water even for long periods of time, it is not decayed significantly by the common decay fungi regardless of the wood species or the presence of sapwood. Bacteria and certain soft-rot fungi can attack submerged wood but the resulting deterioration is very slow. A large proportion of wood in use is kept so dry at all times that it lasts indefinitely. Moisture andtemperature, which vary greatly with local conditions, are the principal factors affecting rate of decay. When exposed to conditions that favor decay, wood deteriorates more rapidly in warm, humid areas than in cool, dry areas. High altitudes, as a rule, are less favorable to decay than are low altitudes because the average temperatures and available moisture are lower. If not in ground contact and kept dry, most woods remain free of rot and have an extended service life.

The heartwoods of common native species of wood have varying degrees of natural decay resistance. Untreated sapwood of substantially all species has low resistance to decay and usually has a short service life under decay-producing conditions. The decay resistance of heartwood is greatly affected by differences in the preservative qualities of the wood extrac­tives, the attacking fungus, and the conditions of exposure. Considerable difference in service life may be obtained from pieces of wood cut from the same species. There are further com­plications because, for some woods, heartwood and sapwood are so similar in color that they cannot be easily distinguished. Also, the marketable sizes of some species are becoming largely second growth and contain a high percentage of sapwood. Consequently, substantial quantities of heartwood lumber of these species are not easily available.

Precise ratings of decay resistance of heartwood of different species are not possible because of differences within species and the variety of service conditions to which wood is exposed. However, broad groupings of many native species, based on service records, laboratory tests, and general experience, are helpful in choosing heartwood for use under conditions

favorable to decay. The groups are exceptionally resistant, very resistant, moderately resistant, and slightly to nonresistant to heartwood decay. The extent of variations in decay resistance of individual trees or wood samples of a species is much greater for most of the more resistant species than for the slightly or nonresistant species. Where decay hazards ex­ist, heartwood of species in the resistant or very resistant category generally gives satisfac­tory service, but heartwood of species in the other two categories will usually require some form of preservative treatment. For more severe decay hazards, pressure treatments are often required; even the very decay-resistant species may require preservative treatment for impor­tant structural uses or other uses where failure would endanger life or require expensive repairs.

Consideration is also given to vulnerability to attack by Lyctus beetles, subterranean and dry-wood termites, and other insects. If data are available, resistance to such attack is reported here.

Preservation: In general, sapwood is more permeable to preservatives than is heartwood. Treatability of sapwood and heartwood using either open tank or pressure-vacuum processes is described. Ratings may range from permeable, where 15 to 20 lb/ft3 (240 to 320 kg/m3) and more of preservative solutions are absorbed with complete or deep chemical penetration, to extremely resistant, where absorption is only 2 to 3 lb/ft3 (32 to 48 kg/m3) or less and lateral penetration is superficial. There is no standard treatability test. Ratings may be based on laboratory trials using a wide range of specimen sizes, with or without end coatings, or on actual commercial treating plant experience.

Uses: Suitability of a wood for particular applications may be based on personal preference, indigenous uses, or experience. Nevertheless, the lists of uses indicate the properties and working characteristics of the wood and may suggest applications still not realized. Trees formerly classified as uneconomic or weed species are now frequently in high demand. Use categories, then, should not be considered restrictive. If a tree is noted for the yield of prod­ucts other than wood (gums, latex, fiber, tannins, nuts and fruits, etc.), this is also indicated.

Toxicity: Wood as a material is not considered toxic or carcinogenic by the Environmental Protection Agency (EPA), but sawdust is. However, almost all woods, including United States native white pine and paper birch, have constituents that are allergenic or toxic to someone. Most people, though, are unaffected by most woods. Dust generated in woodworking may irritate skin and mucous membranes and even cause nosebleeds and respi­ratory disorders. Timbers that are particularly toxic are noted when information is available. If no information on toxicity is available, this does not mean that the wood or wood byprod­ucts are not toxic. If working with the wood is reputed to cause skin or mucous membrane irritations, this is noted.

Cited References and Additional Reading: References are cited by a number or num­bers in parentheses and listed at the end of the report. The references can be used to trace the sources of the reported measurements to determine how representative the data may be. For instance, for some species data from only one tree may have been available, while for others, wood from many trees may have been tested. At the end of each wood description, references for additional information are cited.

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