Monday, November 24, 2008

How do you like your Locust? Black or Honey? On the occasions that I might presume to dispense permaculture know-how on this blog, it’s always from the point of view of the fellow beginner, blundering around in a sea of ignorance, incomprehension and incompetence, rather than me ever claiming to be an “expert”. I think that this can be rather reassuring for a fellow beginner: to read of tales of occasional success set against a background of mistakes and failure, making them feel that their own stumbling progress is quite OK and not to be measured up against the pristine examples of the true expert. Coupled with my vague idea that permaculture knowledge should be ”open source”, I plan to publish a series of FREE permaculture fact sheets under the title of “The Blind Leading the Blind”. Our talented artist friend Alastair has already supplied the artwork, see above.

However much of a beginner you consider yourself, be prepared to question received knowledge; perhaps that approach is actually a requisite of permaculture? Here’s a recent example, which concerns our planting of a few black locust (also known as false acacia and, in Latin, robinia pseudo-acacia) a plant I believed to be an archetypal permaculture panacea. In his The Earth Care manual: A Permaculture Handbook for Britain and other Temperate Climates, Patrick Whitefield (who taught my Permaculture Design Course) says that black locust “provides: fodder of bees, edible seed for chickens, edible foliage for grazing animals, timber … and nitrogen fixation.” p.33. In The Woodland Way: A Permaculture Approach to Sustainable Woodland Management, Ben Law says, “Nitrogen fixing trees like alder and black locust will make a useful addition to any agroforestry system whether over pasture or arable crops.” p.17. So, imagine my surprise when, tucked up in bed one night with a cup of cocoa and Gene Logson’s All Flesh is Grass: The Pleasures and Promises of Pasture Farming, I read that “Black locust... is not a good pasture tree. Its leaves are considered toxic to animals.” Hmmmm?

I searched around on the Internet and came up with this entry on Wikipedia: Unlike the pods of the honey locust, but like those of the related European Laburnum, the black locust's pods are toxic. In fact, every part of the tree, especially the bark, is considered toxic, with the exception of the flowers. However, various reports have suggested that the seeds and the young pods of the black locust can be edible when cooked, since the poisons that are contained in this plant are decomposed by heat. Horses that consume the plant show signs of anorexia, depression, diarrhea, colic, weakness, and cardiac arrhythmia. Symptoms usually occur about 1 hour following consumption, and immediate veterinary attention is required.

Having planted several of the trees where our chickens free-range, with the intention of them grazing on the fallen seedpods, you can see that I was a little concerned. I’ve even planted two in a paddock where the sheep graze. Perhaps I should have planted the thorn-less Honey locust (Gleditsia triacanthos) instead, which Gene Logson suggests “makes an excellent pasture tree.” He goes on to explain that livestock love the sweet seedpods, that the tree does not cast heavy shade so allows the sun to get to the pasture and that “the tree is a legume, so is constantly fixing nitrogen in the soil.”

Reading around books and searching on the Internet, I found conflicting opinions as to whether the honey locust does indeed fix nitrogen, or not. I emailed Martin Crawford of The Agroforestry Research Trust. He replied:
There is some confusion around black locust and honey locust. In the past both have just been called “locust” in North America and the uses of both have sometimes been mixed up.
Black locust is an excellent fast growing n-fixer and a good bee plant. They have more experience of growing it in pastures in Eastern Europe than North America. In Hungary the leaves are valued as excellent fodder, especially for goats and rabbits. Whether it is toxic to horses, I don’t know but it won’t be to sheep if goats are fine with it. However, the seeds do contain toxins when raw, so it is probably not best used as a major feed for chickens. The Hungarians report no problems from ruminants eating the seeds pods.
Honey locust was thought not to fix nitrogen until a few years ago because they don’t produce nodules like most n-fixers. Then someone discovered the fix N through a different mechanism, so now they apparently do. However, I don’t recommend it for France in pastures, as it is very slow growing and will require many years of protection from grazing stock.

I wrote to Patrick Whitefield of my discoveries; he said: “After reading what you’ve written I’ll certainly make an amendment in the Manual next time it’s reprinted and also when I’m teaching. Interesting about Glenditsia too.
Thank you very much. I only wish other people were so free with the products of their research as you are!”

So there you have it, the not-quite-definitive answer to the question I began with. Do question received wisdom and do share the results of your research. Thanks to Magnus for posting a question (as a comment), to which this is, I hope, a useful reply.