Locust wood is exceptionally good for firewood, ranking among the best hardwoods available for heating. The term “locust” generally refers to two species: Black Locust (Robinia pseudoacacia) and Honey Locust (Gleditsia triacanthos). Both are highly valued for their heat output and longevity, though Black Locust is often cited as the superior choice due to its slightly higher density.
Assessing Locust Wood’s Performance
The outstanding performance of locust wood is directly linked to its high energy density, measured in British Thermal Units (BTU) per cord. Black Locust wood contains approximately 26.8 million BTU per cord, placing it near the top of all common firewood species. This high density means a single piece of locust wood contains more usable heat than an equally sized piece of a less dense species, such as Northern Red Oak or Sugar Maple, which typically yield about 24.0 million BTU per cord.
The wood’s density allows it to burn for an extended duration, making it a preferred choice for long burn times and overnight heating. Once established, the dense structure resists quick consumption, releasing heat steadily over many hours. Honey Locust offers a comparable 26.5 million BTU per cord, meaning both species are highly effective at providing intense, sustained heat.
Processing and Curing Requirements
Preparing locust for the firebox involves unique challenges stemming from its extreme density. The wood, especially Black Locust, is notably tough and stringy, making splitting difficult once it has dried and hardened. It is highly recommended that logs be cut and split immediately after felling while the wood is still “green.” Splitting green wood requires less physical force, despite the wood’s inherent toughness.
Due to its high density, locust wood requires a longer seasoning period than many other types of firewood to reach the optimal moisture content of 20% or less. While lighter woods may season in a year, locust generally requires a minimum of 12 to 18 months. For the best performance, some experienced users recommend a full two-year curing cycle, especially for indoor wood stoves. Proper seasoning involves stacking the split wood off the ground in a location that receives ample sun and air circulation.
Safety Considerations and Burning Qualities
Caution is necessary when handling locust wood due to the presence of sharp thorns. Black Locust can be covered in thorns, especially on younger branches, and Honey Locust features large, distinctive thorns on its trunk and branches (though thornless cultivars exist). Wear heavy gloves and protective clothing when processing or handling unseasoned wood to prevent injury.
The wood and bark of Black Locust contain compounds mildly toxic to livestock and humans if ingested. While the toxicity is largely neutralized by the high heat of a fire, it is prudent to avoid using Black Locust sawdust or chips near food preparation areas during processing. Once fully seasoned, the wood burns cleanly and is considered safe for use in residential wood stoves and fireplaces.
When properly seasoned, locust wood produces a fire characterized by minimal smoke and a clean, hot flame. It is well-known for its excellent coaling properties, creating a dense, long-lasting bed of hot embers that continues to radiate heat long after the flames have died down. Ash production is typically low, requiring less frequent cleaning of the firebox. However, the wood’s density and tendency toward internal knots can sometimes cause pieces to “spit” or throw coals in an open fireplace, so a protective screen is advisable.