Black Locust, How Do I Love Thee, Let Me Count the Ways: Hmm. At Least Seven.

In Belize, it sounds daft, but I used to find myself daydreaming about a tree called madre de cacao (Gliricidia sepium). It was a strapping type of tree: tall, quick-rooting, nitrogen-fixing. While living there, my wife Emma and I were doing a work-trade at a local cacao farm, and we discovered this specie, the “mother of cacao”, and instantly put it to work in our gardens. It made for great living fence posts and produced an abundance of rich mulch material, all the while making the area fertile. What more could a young permaculturist want?

When eventually our time in Belize came to a close, I never thought I’d find a tree quite so alluring, until this year, arriving in North Carolina, when I was introduced to a tree that I’d read about from time to time but had never actually knowingly encountered: The black locust (Robinia pseudoacacia). I’ve only become more enchanted since that first day, when the owner of Snaggy Mountain, Jared, told me how the black locust was the best firewood around. We were talking about coppicing trees, and I asked if the black locust would work. He didn’t know. I decide to do some research: Not only would it work, it came highly recommended, and there was a lot more as well.

Like many a good tree (and weed), black locusts are considered by some as an invasive species, but in defense of my new muse, these people perhaps aren’t seeing the full potential of what is. This tree is an incredibly useful, multi-functional addition to permaculture sites, and while it may require some maintenance to prevent spreading (as did madre de cacao), like any appreciated diamond in the rough, it also has the potential to pay back in dividends for those willing to nurture the beauty that is the black locust.

Firewood

Locust borer (Susan Adams)

A big difference between North Carolina and Belize is the climate. In Belize, madre de cacao was appealing because it could be coppiced or pollarded to provide sustainable firewood for cooking, but in North Carolina, the stakes are upped a bit more. In the humid cool winter of these mountains, firewood can be crucial for heating, especially on off-grid homesteads. Not only can be locust be coppiced, but it is also—as Jared pointed out—a dense, hot-burning, long-burning wood. The wood has certain qualities that also help it store for longer than other choices.

Timber

In the same breath, black locust wood is so revered as a timber wood, especially for outdoor items like fence posts and decking, that it almost seems a crime to burn it. It’s rot-resistant, so it’s often the chemical-free version of lumber where treated wood might be used. Because it is fast-growing and quick-spreading, it also makes for a sustainable source of wood, as cutting some back is a necessity. Plus, its strength is compared to that of oak, which means it can do some serious framing work.

Nitrogen-Fixing

The often exalted quality—at least amongst permaculture enthusiasts—of being nitrogen-fixing is something that is always worthy of taking note of. Black locusts are nitrogen-fixing over-story trees that commonly reach up to 24 meters high. They can also be coppiced and pollarded for firewood and fence posts, which would mean that larger quantities of nitrogen are released into the soil when the wood is harvested. For the same reasons, they are potentially a great companion plant in food forests, providing fertility and chop-and-drop mulch.

Edible Flowers

Black locust flowers (Kristine Paulus)

One of the knocks on black locust is that many parts of it are toxic for humans (and horses). The beans, the leaves, the roots are no good for eating, but the flowers are. And, they are absolutely delicious. What’s more is we learned at Jared’s farm that, for those willing to harvest them, there is a market for selling them, that some restaurants will pay high dollar. It’s the same kind of irony as dandelion greens bringing in big dollars in markets: When flowering, black locust flowers are in abundance for free.

Bees

Continuing on with the flowers, bees apparently love to forage from the black locust blooms. It’s known to be one of the top trees for honey bees in the US, and the honey produced from black locust pollen is said to be “fruity and fragrant”. A relatively pure locust honey is also high in fructose, nearly clear in color, and that it makes it—like the wood from locust trees—a viable candidate for long-term storage. The black locust was actually exported long ago to Europe, and it has remained a popular honey-producer there.

Chicken of the Woods

Another exciting part of North Carolina has been the wild edible mushrooms. Mushrooms are widely enjoyed or produced in Central America, so to suddenly have them in such abundance and variety is exciting. One of the most beloved wild edible mushrooms here is the “chicken of the woods” (Laetiporus sulphureus), which just so happens to like growing on black locust trees. In fact, like oak, black locust logs have good characteristics for mushroom cultivation; however, there is debate as to whether the toxicity of the tree ruins the mushroom, so this would require some caution.

Airy Over-story

Sunlight through the Locust (Kristopher Volkman)

A common problem here in North Carolina is a late frost, after apple and other fruit trees blossom, and this is known to decimate crops. A potentially good solution for this (my theory) is allowing some black locusts to grow up as over-story trees. They are known to have rather airy foliage, which will allow sunlight in but, hopefully, provide some protection from cld frosts. We used madre de cacao in Belize similarly, only to dapple the sunlight during the hot dry season, so I see real potential in experimenting with black locust to combat frosts.

Eight, Nine, Ten…So Many More!

Inevitably, as research has proven time and time again, it only takes a fledging interest in a tree or plant, and suddenly, it can be seen in a whole new light, and another, and another. The more I started pondering the potential of using black locust, the more I discovered how it can be used. Some use it for fodder (not for horses!). It is known as a dynamic accumulator. It is obviously, like many quick-growing legumes, a pioneer plant for degraded landscapes, which is why it has a weedy reputation. It’s fantastic for erosion control. It provides an abundance of biomass. It is an adaptable grower, tolerating soils with pH levels down to 5.1 and up to 8.5 and working in climates ranging from USDA 3 to 9. There are only a couple of bugs that bother it. It’s a tolerant of juglone, a growth inhibitor released by black walnut (common here), which makes it a potential buffer tree. It’s a great shelter for small animals, and hummingbirds love it. For that matter, I think I do, too.

Well, the love story has only just begun, and I’ll admit that everyone is smitten at the beginning of a relationship. But, I can just really see this one going somewhere. I know some folks might only see the invasiveness and toxicity, but there’s more to the black locust. I’m sure of it. Let’s just hope I’m burning it, and it’s not burning me.

Header Image: Black Locust Label (Wendy Cutler)

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13 thoughts on “Black Locust, How Do I Love Thee, Let Me Count the Ways: Hmm. At Least Seven.

  1. Jonathan,
    I’m interested in your idea of using Block locust as an overstory providing protection for fruit crops from cold frost. Any research or anecdotes of others you’ve heard that would indicate if works?

    Also, I would imagine the dappled shade could benefit understory fruit crops during droughts, maybe reducing irrigation needs?
    Let me know your thoughts.

    Jared

  2. The leaves applied to viral skin infections such as shingles are of medicinal value too. Tested it on an infection on my wife and cleared it within days! The very young pea pods are edible too, as long as they are cooked.

  3. This article took me back about fifty years or more when we first moved to our 5-acre “farm” in northeast Ohio. The fragrance of black locust in bloom and the sound of foraging honey bees is only a small part of those memories. I still have honey from back then, and I prize it like gold.

    I use black locust planks for my raised beds, and they are only beginning to deteriorate after almost fifteen years’ contact with the soil. . . after which the useless portion is removed in order to make smaller beds and retainer stakes.

    I also used the occasional black locust wood in our wood stove after learning its BTU output is the same as bituminus coal, according to a university study of various hardwoods.

    I have also used black locust for some incidental furniture, and it’s quality is easily comparable to the finest oak.

    Thank you for reminding me of what I miss after needing to move back into a more urban area.

  4. Hmmmm. Have you ever tried to cut down an 10″ diameter black locust? No chain saws, just a crosscut saw. Have a go. LOL. Then think what doing a winter’s worth might be like.

    No saying it’s not a good tree in the ways that you mention, just that there’s more to firewood than BTU’s.

  5. I love Black Locust but one thing folks should know about is that it has really vicious thorns! Straight thorns that are approximately one to one and a half inches long.

    But it is a really fast grower, which makes it great for short rotation coppicing, which is why it garnered my interest in the first place.

  6. Thanks for this. My ancient black locust, with huge trunk, is dropping smaller limbs and getting draped in vines as it dies. Going to cost a bundle to have it cut down. Guess I’ll just collect limbs that fall off for winter burning. And treat the smaller ones with more respect!

  7. What about Honey Locust etc.
    Are other members of the family good for fire wood too. How long do the suckers remain with the thorns?
    The flowers part was interesting as well.

  8. Black Locusts have been in Australia quite a while. There was an experimental plantation near Armidale NSW on forestry land. It failed but I believe the trees are still present. I think the trees may also have come over with the gold rush folk from California in the mid 1800s. There’s no doubt about their honey production or nitrogen fixation here but I gather the lumber / fuel wood side of things is not so guaranteed. I also recall a child hood experience of a very productive untended peach tree under a copse of Black Locust so they probably could be useful as an overstorey. However, don’t underestimate their ability to sucker, often a long distance from the tree itself. Cheers, Alex.

    1. We have these trees all over the place in the Netherlands. About 25 years ago, I used to work in a park maintenance crew in the new town of Almere, in one of the young polders. The ground is so fertile there, that trees look like they’re 25 years old after just 10 years. One day a lady came up to us and asked us to have a look at something in her house. We saw a tiny green shoot coming out of the inspection hatch handle in the floor. But once we opened up the hatch, the whole crawl space underneath the house was filled with a crawling mass of white roots. It turned out this was from a relatively young Locust tree over 20 meters away! Yes, they are invasive, and have nasty thorns too, and yes, great firewood, beautiful tree, long lasting wood for outdoors (it’s sold here as a replacement for tropical hardwoods). But the wood is also very curly-grained, not a straight grain in sight, and the bark is full of deep pockets and undulating.

  9. I’ve planted hundreds of these things for coppice wood, and many of the other reasons mentioned in the article.
    Another note on the firewood side is that you can burn the freshly cut wood green in the wood stove. It still burns. Not as well as seasoned wood, but still, it could save your life if you have to cut and burn the tree the same day.
    Another note that was missed in the article is tree rain. These things (like most big trees) harvest moisture out of the air and drip it down to the soil. So if you are using them in your orchard, they can also help water your understory plants.
    And a third point – if you are going to use the wood for fence posts, make sure it is seasoned. If you set the post while the wood is still green you are going to have another tree. They root very easily.

  10. Friends in town have a mature black locust in their yard. They have to pick up the seed pods and we have an agreement. I haul off the seed pods for them by the trash can full for my sheep, goats, and pigs. The protein content is high and the livestock act as if I’m giving them candy. I store the seed pods and feed them in the winter and when the livestock is pregnant or lactating.

  11. Wood should be cut and chopped when cut down, don’t wait to season or it will ruin chainsaw or any other saw.
    There are thornless cultivars of robinia and also gleditsia.

  12. Black locust comprises almost a quarter of the forests in Hungary. There has been lots of selections for different uses. Several articles available online. You might find the book “The Black Locust”, Béla Keresztesi, 1988 in a university library.

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