American Elm (Ulmus americana) is a medium-density hardwood that can be used effectively as firewood, but its preparation presents significant challenges. It falls into a mid-range category, providing acceptable heat once properly seasoned, but demanding considerable effort before it is ready for the firebox. While it does not deliver the peak performance of premium species like oak or maple, American Elm is a solid, usable fuel source.
Energy Output and Efficiency
The heating value of American Elm places it in the middle tier of firewood species, delivering approximately 19.5 million British Thermal Units (BTUs) per cord. This output is substantially lower than that of top-tier hardwoods like White Oak or Sugar Maple, which yield closer to 24 million BTUs per cord. The difference in energy output is directly related to the wood’s density.
American Elm’s lower-than-average density for a hardwood, around 35 pounds per cubic foot, is the primary reason for this reduced heat output per volume. Despite this, it is a much better heat source than common softwoods like Eastern White Pine, which offers only about 14.3 million BTUs per cord. Elm is best utilized when a moderate, sustained heat is desired, rather than the intense heat provided by denser species.
Processing Difficulties and Seasoning Time
The most significant drawback to using American Elm is the labor required to process it into usable firewood. The wood possesses an “interlocked grain” structure, where the fibers twist and weave together rather than running straight. This makes it notoriously difficult to split with a traditional maul or wedge, as the grain resists the splitting force.
A powerful hydraulic log splitter is often recommended as the most practical tool for handling American Elm rounds. Splitting pieces into smaller slabs from the perimeter is often easier than driving a wedge directly through the center of a round. Furthermore, elm has a high initial moisture content, meaning it must be seasoned for a considerable length of time. American Elm typically requires 18 to 24 months of seasoning to drop its moisture content below the optimal 20% level for clean burning.
Fire Characteristics and Residue
Once thoroughly seasoned, American Elm burns at a moderate pace, providing a steady heat output rather than a quick, intense burst. The wood is well-regarded for its excellent coaling properties, forming a good bed of long-lasting, hot embers. This makes it an effective choice for maintaining a fire overnight or for banking a stove.
Properly dried elm produces a moderate amount of smoke and does not tend to spark or pop, making it a safe option for open fireplaces. If the wood is burned green, the high moisture content will cause excessive smoke and a noticeable odor. The ash residue produced by American Elm is moderate in amount and may sometimes form clinkers, which are hard, fused deposits that require periodic removal from the firebox.
Sourcing Elm and Disease Concerns
The availability of American Elm firewood is linked to the historical devastation caused by Dutch Elm Disease (DED). This fungal infection, spread by the Elm Bark Beetle, has dramatically reduced the population of large, mature American Elms. Consequently, much of the elm wood available for firewood is salvaged from trees that have died or are dying from the disease.
Wood from DED-killed trees can be dry on the outside but still hold substantial moisture in the core. This requires immediate splitting and proper stacking to prevent rot and insect infestation. Moving elm firewood carries the risk of spreading the beetle and the fungus to healthy trees in new areas. Therefore, it is important to check for local regulations or quarantines that restrict transporting elm firewood across county or state lines.