Yes, hackberry is classified as a hardwood. The common hackberry, scientifically known as Celtis occidentalis, is a large, deciduous tree native to a wide range across North America, particularly the eastern and midwestern United States. This classification is based purely on the botanical family of the tree, not on the physical density or strength of its harvested lumber. This botanical designation dictates the fundamental structure of the wood, which in turn influences its material properties and utility.
The Botanical Definition of Hardwood
The term “hardwood” refers to a biological classification based on a tree’s reproductive method, placing it within the Angiosperm division of plants. Angiosperms are flowering plants that produce seeds enclosed within a fruit or protective casing. These trees are typically deciduous, meaning they shed their broad leaves.
This biological structure distinguishes hardwoods from softwoods, which belong to the Gymnosperm division. Gymnosperms, like pines and spruces, are conifers that produce “naked” seeds, often in cones. Furthermore, the internal wood structure of hardwoods contains vessel elements, or pores, dedicated to transporting water throughout the tree, which are absent in softwoods.
Hackberry fits squarely into the hardwood category because it is an Angiosperm that produces a small, fleshy fruit called a drupe that encloses its seed. However, the name “hardwood” can be misleading because the actual physical hardness of the wood varies significantly among species. For instance, balsa is technically a hardwood, yet it is much softer than many softwoods, illustrating that the term describes botany, not strength.
Key Characteristics for Identifying Hackberry
Identifying the living Celtis occidentalis tree is relatively straightforward due to several distinct features, especially its bark. The mature bark displays a grayish color with prominent, cork-like ridges and distinctive warty protuberances. These unique, irregular ridges give the trunk a texture unlike most other common North American deciduous trees.
The leaves also possess a specific anatomy that aids identification. Hackberry leaves are simple, ovate, and have a noticeably asymmetrical base. The leaf edges are coarsely toothed, or serrated, primarily from the middle to the sharply pointed tip.
During the late summer and fall, the tree produces small, round, berry-like fruits known as drupes. These fruits transition from orange-red to a dark purple color when ripe, often persisting on the tree throughout the winter months. The slender twigs often exhibit a slightly zigzag growth pattern, which is apparent when the tree has lost its leaves.
The hackberry is highly adaptable and can be found growing in a wide range of conditions, from moist woods along streams to drier upland slopes. Its tolerance for various soil types and urban pollutants has made it a common tree across the eastern and midwestern United States.
Practical Uses and Material Properties of Hackberry Wood
Hackberry wood is moderately heavy, with an average dry weight of about 37 pounds per cubic foot, giving it an intermediate density among hardwoods. The wood’s color is generally light, featuring a yellowish-gray sapwood and a light brown to grayish heartwood. Like elm, the wood is ring-porous, and its grain can be straight or sometimes interlocked, which can make machining and surfacing challenging.
Despite being softer than many traditional hardwoods like oak or maple, hackberry exhibits a high resistance to shock. This shock absorption, combined with its excellent performance in steam bending, historically made it suitable for use in barrel hoops and curved furniture components. It is highly valued for steam bending applications.
Modern applications for hackberry wood include inexpensive furniture, kitchen cabinets, and interior millwork, where it is sometimes utilized as a substitute for ash due to its similar appearance. The wood’s lack of natural resistance to decay means it is not recommended for exterior use or any application exposed to moisture. If not processed immediately after felling, the light-colored wood is highly susceptible to fungal and oxidation staining, resulting in blue-gray discoloration.