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Home | Articles | What's in a Name?: The Science of Wood Identification

by Harry A. Alden

The underside of a New York sideboard drawer, 1795–1805, is identifiable on a macroscopic level as tulip poplar (Liriodendron tulipifera) because of the greenish band of color that is the tree’s heartwood. Image courtesy of Sumpter Priddy III, Inc.

Microscopic wood anatomy and identification are often used to help authenticate antiques and determine their origin. As a professional in wood anatomy and identification, I frequently encounter instances of woods being misnamed. I was recently sent a wood sample used in the making of a colonial doorway that was initially referred to as 'hard white pine.' In fact, there is no such thing. Hard pines are in the yellow pine group; white pine, which is much softer, is in the white pine group; the wood cannot be both at the same time. This type of faulty nomenclature is understandable given that the erroneous terms are in common use, but it can result in incorrect assignments, leading to faulty scholarship and, in the marketplace, financial repercussions.

When describing furniture woods, nonscientists generally use the 'trade' name to communicate effectively and accurately (i.e., the most commonly recognized vernacular name), in addition to, or in place of, the scientific name. The scientific names are the product of a binomial system developed by Carl Linnaeus (1707–1778), in which each specific type of plant is given a binomial ('two-names'): the genus (like our family names, e.g., Smith) and a species name (like our first names, e.g., John). The binomial always appears in italics, with the genus first, e.g., Pinus, and the species epithet second, e.g., strobus, as in Pinus strobus, the scientific name for eastern white pine. When a species is unknown, the abbreviation 'sp.' in the singular and 'spp.' in the plural are used in place of the specific epithet. Similar genera are grouped into families (with names ending in –aceae), similar families into orders, similar orders into classes, and similar classes into divisions.


Definitions
Hardwood: broad-leaved trees like oaks and maples
Softwood (conifers): evergreen trees that produce cones and usually have narrow, needle-shaped leaves
Primary wood: Comprising the 'show' material
Secondary wood: Comprising the structural material

Macroscopic views of oaks (Quercus spp.), showing differences in ray height (arrows), as viewed on the flat-sawn or tangential surface. Furniture made with red oak as a primary wood can indicate its American origin.

Using the scientific name is the best way to avoid confusion, but since Latin names can be difficult to pronounce and remember, trade or common names are most often used. In general, this scheme works well, but there are many times when confusion occurs. For example, the term 'poplar' can represent the tulip poplar (Liriodendron tulipifera), a secondary wood common in colonial furniture, or the true poplars (Populus spp.), a wood that appears in European furniture. The term 'sycamore' is the genus Platanus in America, but in England and Europe the term refers to a species of maple (Acer pseudoplatanus).

Common names also differ between countries. The genus Tilia, for instance, is known in America as basswood (used as a secondary wood) and lime in England. Some species have numerous common names as a result of each country or region having developed its own distinctive term. For example, there are at least 135 common names for rosewood, 446 for mahogany, and 475 for cedar.


Clapp family desk, dated March 12, 1807. Inscribed by the maker, 'Robert Matthews.' Guilford County, North Carolina. Walnut primary wood. H. 42, W. 36-7/8, D. 21 in. Private Collection; image courtesy of Sumpter Priddy III, Inc.

Some common names are just plain inaccurate. Spanish cedar (Cedrela odorata) is neither a true cedar nor from Spain, but is so named because it was discovered by the Spanish in Central & South America and because it has a strong cedar aroma. The true cedars (Cedrus spp./Pinaceae family) are native to North Africa, the Middle East, and Asia. There are no true cedars in North or South America, but we use the term to describe fragrant woods like eastern red cedar (Juniperus spp.), northern white cedar (Thuja occidentalis), western red cedar (Thuja plicata) and Atlantic white cedar (Chamaecyparis thyoides).

The assignment of origin based solely on microscopic wood identification is virtually impossible; other factors need to be considered when assessing an object. Since the sixteenth century, trees have been carried from one geographic location to another. Eastern white pine (Pinus strobus) from the American colonies, for instance, was imported into England in the mid-seventeenth century as a horticultural curiosity. Objects transported across the oceans by boat were packed in wooden crates, which, instead of being discarded, were put to good use in the manufacture of other objects. Thus something like Scots pine (Pinus sylvestris) and spruce (Picea spp.), indicators of English/European provenance, can be found as secondary woods in Colonial furniture and backings for looking glasses.


Right: American black walnut (Juglans nigra). Macroscopic view showing growth ring boundaries as dark lines (vessels and pores).

American black walnut is native to the United States. Its use as a primary wood in antique furniture is considered an 'indicator' of an object’s origin.

While most species groups appear on both sides of the Atlantic or Pacific, a few genera or species have very limited natural distributions and are good 'indicator' woods. For example, bald cypress (Taxodium spp.) contains two species that are only native to the mid-Atlantic and southern United States. Its presence in an object likely indicates that the object originated in America. Other woods seen in Colonial furniture that suggest indigenous origin are American black walnut (Juglans nigra), the white pine group (Pinus spp.), the red oak group (Quercus spp.), the hickories and pecans (Carya spp.), tulip poplar (Liriodendron tulipifera), Atlantic white cedar (Chamaecyparis thyoides), and northern white cedar (Thuja occidentalis).

Tilt-top tea table, Philadelphia, ca. 1765. Mahogany primary wood. H: 28-1/4 (top down); Diam. 35 in. Image courtesy of Sumpter Priddy III, Inc.

How is microanalysis actually used in discerning the difference between woods such as American or European walnut? Through cell structure. In the walnut/butternut group (Juglans spp. Juglandaceae), American black walnut (J. nigra) can be separated from English/European/Persian walnut (J. regia) by the presence of short chains (1–5) of calcium oxalate crystals in the axial parenchyma of the wood as well as irregular spiral thickenings in the vessels termed 'gashes.' In other cases, species separations are identified through empirical methods. For example, in true mahogany (Swietenia spp. Meliaceae), if the specific gravity (density) of the wood is above 0.65, then the wood is Cuban mahogany (S. mahogani) and not Honduran mahogany (S. macrophylla). If the specific gravity is below 0.65, either species may be present.

Wood identification does not, by itself, determine the origin of an object, but, used in tandem with construction and aesthetic features, plays an important role in the attribution of furniture and decorative arts.




RIGHT: True mahogany (Swietenia sp.).
Macroscopic view showing growth ring boundaries
as white lines (marginal parenchyma).

Mahogany is a common name that represents numerous unrelated tropical hardwoods. True mahoganies consist of three species in the genus Swietenia native to the Caribbean, Central, and South America. African mahogany is a different genus Khaya but the same family (the Meliaceae). Philippine mahogany is the genus Shorea, while Horseflesh mahogany (Caribbean origin) of the genus Lysiloma are in separate plant families unrelated to true mahoganies.

Dr. Harry A. Alden is co-owner of Alden Identification Service (www.woodid.homestead.com/ais.html), which provides microscopic identification of natural materials from archaeological, fine and decorative art objects. He has worked at the USDA Center for Wood Anatomy and for Winterthur Museum, and the Smithsonian Institution.


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