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Tuesday, December 28, 2010

Black Locust

Last year I had a chance to work with black locust, a wood that is fairly common here in the eastern U.S., but somewhat hard to find as lumber. A neighbor had four large trees removed, and I got the wood and split it all for firewood last winter. It burned hot and steady, and made a coal almost as nice as oak. The only downside to it is a rather pungent odor in combustion, and I wondered all winter whether one of my neighbors was going to say something to me about it. But they didn't, and I was blessed with a lot of heat from about three cords of locust.

I also had a chance to write a story about some folks here in central PA who decided to build their deck from black locust lumber. Here is the link to that story. I wrote it up after the couple contacted me for some help in locating the black locust, and I followed their progress from there. The resulting technical note has become the most-viewed article I've ever posted on my Penn State site. I think building decks is a popular topic of inquiry and interest, so I'll try to include some deck stories in future posts.

Black locust has a great history in American farm life. It was the preferred fence post in the East for almost two hundred years, because of its rot-resistance. Many are the stories of fifty-year-old black locust fenceposts. In his great classic, A Reverence for Wood, Eric Sloane described black locust in this way:

The scraggly locust that looks like a dying tree even at its best, during the summer...

Charles Fergus, in his Trees of Pennsylvania and the Northeast, gives a nice description of locust wood and its historical uses:

Black locust wood is very heavy, at 52 pounds per cubic foot. Hard and strong, it is stiffer than hickory and more durable than white oak. Its fuel value is among the highest of any American tree: a cord of black locust contains as much heat energy as a ton of anthracite coal; the wood burns cleanly, with a blue flame. Because it lasts for years in contact with the soil, black locust is the top choice for a post: a locust post has held our our mailbox for twenty years, and will probably outlast my tenure on the place. The heartwood is an attractive yellowish brown to cherry red color, surrounded by a narrow band of greenish or yellowish sapwood. People have fashioned the tough wood into trunnels ("tree-nails") for holding together the wooden frames of ships, insulator pins on telegraph or telephone poles, ladder rungs, buggy hubs, and policemen's billy clubs. Other use include mine timbers, railroad ties, boxes,crates, and stakes.

source: Brightwork

Early colonists in Jamestown, Virginia, cut locust corner posts for their dwellings. Those same settlers named the tree for its supposed resemblance to an Old World species, the carob, Ceratonia siliquia, also known as the locust; one wonders if the settlers had ever actually laid eyes on Ceratonia siliquia, which grows in the Mediterranean region. Other names for black locust are honey locust, yellow locust, white locust, common locust, and false acacia.

Yikes! I'd hate to get whacked with a black locust billy club!


Peter Griessmann said...

Hi. Read with interest about the eastern black locust. We also have this species(abundantly) in the Inland NW. I have a small wood supply business in Addy, WA and work w/ some tree removal folks in getting the larger diameter logs. We make slabs and some lumber from these trees. The wood is light brown (Heart) and creamy white (sap). It is very hard and makes pretty good turning wood. Would anyone know the difference in Black vs. Honey locust. I understand honey locust to be blonder heartwood not as dark as the black locust. I have the chance to acquire some honey locust and am wondering how it behaves (in service) finishes, turns etc...Ideas??

Chuck said...

Great questions for a future post, Peter. A lot of people seem to have an interest in black locust and honeylocust...they're kind of underutilized local species that have excellent multiple uses (and an interesting history). I'll try to follow up with a post next week...

Bill Kennedy said...

I build replicas of prehistoric Native American structures for an open-air outdoor archaeological museum in Dayton, Ohio ( I build almost exclusively with Black Locust, setting the posts in the same postholes where similar structures stood about 700 years ago. I use the timber in the round and make joinery with simple mortise and tenon joins. It is essentially a highly modified form of timber framing. The prehistoric people who lived here would have used White Oak, but I use locust for practical and ecological reasons. It takes an astonishing amount of wood to build this type of architecture (200 small to medium sized trees for a 20x30' structure). I work with a professional thatcher from Ireland to put thatched roofs of prairie grass on top. My experience with Black Locust has never been in sawn form, only as natural timber. I use modern tools and modern fasteners for non-load bearing elements. I can tell you that Black Locust does have smell when you work it - it's the smell of your drill motor burning out. One of the things that's great (or terrible depending on your perspective) is that Black Locust is very hardy tree. Cutting it down tends to just make it angry. Cutting locust is effectively just coppicing it, plus it will send out runners. If you want a nice dense stand of locust, cut down one old tree and stand back. It's fast-growing so within 15 years, you'll have a FOREST of straight 4" diameter trees around that original stump. We use no chemical treatment, so it's quite amazing to watch these posts. After 5 or 6 years in the ground, virtually all native woods will be completely eaten through by the subterranean termites, but the locust is as good as the day you put it in the hole. Honey locust is nowhere near as good in any sense. It's far more crooked, not decay resistant below grade, and despite a similar appearance, has little in common with Black Locust. Thornless honey locust is a popular street tree in our region so people frequently confuse them because of the artificial absence of the honey locust's thorns.