Photo Credit: Christopoher Evan www.rtrcwma.org

Using Black Locust Around the Home and Yard

Black Locust is considered a “weed tree” and is a much underutilized wood. But a weed is just a plant growing where you don’t like it. Black Locust’s grain is uneven and wavy and the trees do not grow exceedingly large or straight, so it has limited commercial appeal. That’s good, because this tree is abundant and has two very useful properties. It is harder than hickory, and more decay resistant than cedar. In fact an old New England saying goes: “A black locust fence will last as long as a stone fence - plus a day!”

Abraham Lincoln used to split it for fence rails and posts, and it will last over 100 years in soil. Native from Pennsylvania to Georgia and west to Oklahoma, black locust is widely planted elsewhere - it’s very common here in New England, having been used for generations for posts. It is one of the heaviest and hardest woods in North America, and is beginning to replace rain forest hardwoods in applications in Europe, helping to conserve rainforest species.

A member of the pea family, black locust fixes nitrogen in the soil, so it’s great tree for making soils more productive and fertile, eliminating the need for fossil fuel based nitrogen fertilizers.

The tree grows rapidly, and makes excellent firewood to boot, with a clean burn and higher heat content than any other widely grown species - comparable to anthracite coal! Being renewable, it is carbon neutral over the long haul.

Pressure treated lumber on the other hand, was widely treated with chromated copper arsenate (making it green) until it was banned in 2004, and is now generally treated with other chemicals, like copper azole, propiconazole, and cyproconzoazole, all treated as pesticides, requiring special handling, and hazardous to inhale and in some case, handle. Why do you think those carpenters installing the stuff wear masks and gloves? Black locust’s decay resistant properties come from Ma Nature, via naturally occurring flavanoids in the wood.

Here are a couple of black locust applications I’ve done:

Roof joists for my sod roof over my sauna. Because the roof weighs about 15,000 pounds, a lot of damp dirt up there) I wanted something that would hold it and stay decay resistant in the sauna. Black Locust logs spaced every two feet do the trick. It's bending strength is better than oak, comparable to hickory. Don’t want my sod crashing down on my head in the sauna!

Play set for the kids made out of black locust logs and planks. I put the logs right into the ground about 4 feet deep - they’ll be there till my kids are grandparents! I purchased the hardware for the set from a company that used recycled plastics in their products. First thing to go on this set will be the steel chains.

Here's our black locust compost bin. This two sided one lets the bears and raccoons eat what they want and the rest goes on the garden after a year or two. The front panels remove for easy shoveling and turning. This compost bin will last long after I’m compost myself.

So there you have it. What projects do you have that could use a naturally decay resistant wood? A deck, a, fence, an arbor, sills for an outbuilding - black locust will save resources, and last forever - plus a day.