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Black Locust Part II

Garth Brown |

Last week I introduced Black Locust trees with 9 positive points for consideration. In this post I’ll begin exploring those points in greater detail, and I’ll finish discussing them in part III next week.

The many commendable features of Black Locusts were well appreciated by peasants across much of Europe before the advent of our modern fossil fueled lives. Black Locusts are native to eastern North America and crossed the Atlantic sometime in the 1600s. They rapidly spread across Europe as they were highly valued by people living close to the land, meeting their day to day needs with materials readily at hand. Their many uses included fodder for livestock, fuel for homes, and lumber for construction. Today the nation of Hungary is perhaps the pre-eminent home of the Black Locust. Several generations of selection for upright form by tree breeding specialists have provided the Hungarian forest services with the best trees in the world (from a lumber perspective at least). Apparently about a ¼ of the forests in Hungary are entirely or mostly Black Locust.

As a legume Black Locusts can fix atmospheric nitrogen into the soil. Legumes are not the only plants with symbiotic soil bacteria that perform this useful feat, but they are the best known plant family with this special relationship. Nitrogen is usually the first limiting nutrient for plant growth. Anything one can do to increase stores of it in the soil will raise total plant productivity and improve soil fertility. Boosting nitrogen available to a plant will generally (up to a point) make it grow faster, bigger, and make its leaves more nutritious. This is one of the reasons Locust is such a high performer in the world of tree growth. It’s also amazing to me that Locusts can grow as fast as they do without intercepting more sunlight than they do. Perhaps if one didn’t care at all about the other possible uses for the trees they could select for a denser crown of leaves and thus get even faster growth, but the other possible uses for locusts are too wonderful for me to have any desire to pursue that end.

Light shade is marvelous for livestock on summer days. Partial shade allows grasses to grow (food for grazers) and can knock several degrees off the daily high temp the animals are exposed to. All livestock are susceptible to heat stress - in my opinion really hot muggy days are harder for cattle and sheep to deal with than -20 degree nights. I read a study on sheep under a partial “silvopasture” canopy that compared them with sheep on an open pasture. Even though the silvopasture grew less grass over the course of the season it produced just as much meat/acre. The authors attributed this to less heat stress on the growing lambs under the trees, and perhaps to better feed value of grasses grown in more moderate conditions vs open grown pasture.

The benefits of silvopasture don’t end with the grass either - Black Locust leaves are nutritious in and of themselves. Their leaves are protein rich feed for ruminants. Of course often the animals need human help to reach the leaves, but thinning of a locust grove is required to keep the trees from crowding each other too much. I feel obliged to mention that some texts claim locust fodder can cause toxicity problems for livestock, so if you have animals and plan to feed them locust leaves, make sure they have other plants to eat as well. I also know a number of people who routinely feed locust leaves to their ruminants and don’t have any problems… caveat emptor and all that…

While I’m dealing with grazing under locust trees I should visit the bamboo grove idea. One of the issues I’ve struggled with concerning bamboo as a grazed feed is how to get it enough nitrogen into the soil. Bamboo is a grass and will feed heavily on nitrogen given the opportunity. But I’d rather not purchase in nitrogen (whether from a synthetic or organic source) if it can be had for “free” from the atmosphere. In a typical pasture both red and white clover perform well in my climate and fix nitrogen on my soils. But bamboo grows too tall and too thickly to allow these two legumunious forbs to thrive in its company. They’d both be shaded out by the tall bamboo stalks. Locusts on the other hand will easily overtop the bamboo and pump nitrogen into the soil to enrich the bamboo… I’m still years from actually proving this concept, but I think it’s a good enough idea that it is worth testing extensively and I have plantings started to do exactly that.

Another trait that makes Black Locust trees a good fit for the silvopastoralist is when locust trees fall (logging, fire, wind-throw, etc) they have a proclivity for suckering. Vigorous suckering may create problems for the small holder on a suburban yard, but on a broadacre grazing farm anything palatable to cows that will regenerate itself with maximum gusto is a plant I want in my life.

Next week I’ll finish going over the many wonderful traits of these amazing trees.


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