Elm wood, sourced from species like the American, Slippery, or Siberian elm, is often available as firewood, presenting a mixed profile for consumers. While it is a dense hardwood that provides good heat, its characteristics mean it is not always a top-tier choice for the casual user. Elm is a usable fuel source, but the wood demands specific, labor-intensive preparation and careful management, especially concerning disease.
Performance as a Fuel Source
Elm wood offers a medium-grade heat output, placing it below premium hardwoods like oak or maple. American elm, for example, yields around 20.0 million British Thermal Units (BTU) per cord, while Siberian elm is slightly higher at approximately 20.9 million BTU per cord. This heat output is comparable to wood like black cherry or ash, making it an effective choice for heating a home.
The density of elm is an advantage once the wood is properly seasoned and burning. This high density contributes to a relatively long burn time, allowing for sustained heat without the need for frequent reloading. Elm also has excellent coaling properties, generating a long-lasting, deep bed of coals that continue to radiate warmth long after the flames have died down. When thoroughly dried, elm tends to burn with low to moderate sparks, a safety feature for open fireplaces.
Challenges in Processing and Preparation
The primary difficulties associated with elm wood stem from its structure, which complicates both splitting and drying. Elm possesses an interlocked grain that is often described as “stringy” or “cross-grained,” where the wood fibers do not run straight along the log. This structure makes hand-splitting arduous, as the fibers resist separating cleanly, frequently requiring a hydraulic splitter for efficient processing.
The wood’s high initial moisture content and density necessitate a significantly longer seasoning period compared to other common hardwoods. Freshly cut elm can hold over 50% moisture by weight, and its dense cellular structure is slow to release that water. A minimum seasoning time of 12 to 18 months is recommended, and some suggest up to two years for optimal results. Proper stacking is necessary, with the wood raised off the ground, covered from above, and exposed to sun and wind for adequate ventilation.
Handling Elm Affected by Disease
A unique consideration for elm is the presence of Dutch Elm Disease (DED), a fungal infection spread by the elm bark beetle. The beetle uses elm wood with intact bark as a breeding ground. Storing infected wood allows the next generation of beetles to emerge and carry the fungus to healthy trees, requiring immediate action to prevent the spread of the pathogen.
Infected elm wood should not be stored or transported, and must be processed quickly to eliminate the beetle habitat. The standard protocol is to dispose of the wood immediately by chipping, burying, or burning. If the wood is used as firewood, it should be burned before the bark beetles become active in the spring, meaning it must be consumed before the next season. This strict timeline ensures that the fungus-carrying insects cannot emerge and fly to nearby healthy elm trees.