A forum member recently asked about creating silvopastures for their goats with black locust.  In my opinion, black locust is just about the perfect tree for converting open pasture areas into silvopastures.  Some notable qualities include:

  • Very fast growth compared to most other tree species, when properly managed
  • Highly-durable and dense wood that is ideal for firewood, posts, and outdoor use
  • Attractive lumber that is dimensionally stable for carpentry applications
  • Easy to establish compared to most other hardwood species
  • Regenerates well through coppice (stump sprouts) and suckers (root sprouts) in full sunlight
  • Less susceptible to deer browsing than most other hardwoods, and free of serious pests
  • A legume that makes nitrogen available for other plants and increases soil fertility
  • Many other trees and plants will grow well beneath the light shade of its canopy
  • The flowers are attractive and make an excellent seasonal bee fodder
  • The foliage is a nutritional and anthelmintic (deworming) feed for some livestock

On the downside, black locust can spread into unwanted areas by seed and suckers, and has thorns on the juvenile wood (new growth) that can puncture tires and skin.

The most significant pest of black locust is the locust borer, which can damage and occasionally kill young trees.  Vigorous, fast-growing locust are considered to be much less susceptible to borer damage than those struggling to grow on poor sites, or due to drought or weed competition.  Adult borers emerge in late summer and feed on goldenrod pollen before laying eggs on the bark of young locust, so controlling this food source through mowing or spraying may help reduce borer populations and damage.

Black locust has the potential to be a profitable timber crop if well-managed on a decent site.  The selection of quality planting stock, good site preparation, and maintenance until trees are well established will enhance the growth, survival and profitability of the plantation.  There is considerable genetic variation in black locust as to form and straightness.  Care should be taken to select planting stock from “improved” (straight) selections of locust to maximize the yield of usable posts and sawtimber.

After planting approximately 700 trees/acre (about 8’ x 8’ average spacing, in whatever design seems most convenient), thinning should occur about every five years starting at year fifteen.  For best results, cull the smaller and poorer quality trees for posts and firewood in each thinning.  The plantation can be managed on a short rotation (< 25 years) for posts, or longer rotation for posts, poles, sawtimber - and of course, shade for the livestock.  Round posts from locust are currently in high demand and sell for $6 to $12, depending on size and quality.  Poles can be worth several times that, and are also in demand for applications like hops plantation trellises, pilings and pole barn construction.  Black locust lumber retails for $3 to $6 per board foot.   Once a plantation reaches maturity based on the desired mix of products, the remaining best quality trees can be clearcut during the dormant season to stimulate vigorous coppice and sucker regrowth.  These second-growth plantations will have a high number of stems per acre and will require thinning at an earlier age to promote the growth of the best individuals.

Suckers and stump sprouts will result from trees that are harvested during intermediate thinnings, but tend to die out after 1 to 2 seasons under a canopy of larger trees (locust is very shade intolerant).  Allowing livestock to browse the sprouts only lightly and very occasionally when the leaves are out may help this source of browse persist longer. 

Most literature points out the potential toxicity of locust browse from condensed tannins.  We have not experienced any issues with our animals eating locust foliage - but graziers should experiment with caution.  Susceptibility to tannins is probably a combination of: adaptation; health of the animal's immune system; supplemental forages, minerals and plant compounds (from other grazed and browsed plants) that can help dilute or bind the tannins; stage of maturity of the locust foliage; growing site; type of livestock; etc.  Everyone's farm, animals and conditions will be different - so beware!

 

 

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Brett, thank you so much for your thoughtful response to my questions about black locust! Very informative!!

You suggest 900 trees per acre for an initial planting.  How long would you guess you would need to wait (in years) before you could allow beef cattle to graze the pasture you planted these trees in?

What are your thoughts on 50/50 Black Locust/Honey Locust?  Perhaps keeping some of the BL in a browse height (my cattle love it) and having the HL to provide those high sugar pods for a supplemental late season source of food?

My original post suggests about 700 trees per acre.  This would be approximately 8x8 spacing, though I think that other spacings, trees per acre and configurations (e.g. narrow and wide rows, clumps, etc.) could work.  Goal would be to allow enough space between trees so that they'll continue growing "well" for the first 10-15 years until the first "commercial" thinning for posts - vs. having to do a "pre-commercial" thinning (before smaller trees reach minimum post diameter) in order to maintain acceptable growth rates.  Just how long that will take will depend on various factors like site quality, initial care of the plantation, and location (i.e. Maryland vs. Maine).

I think that mixing other species into the planting like honey locust could offer a number of important advantages, not least of which are reducing the risk of pest issues.  Charlie Feldhake at the ARS lab in Beaver, WV found that planting pure groups of honey locust or black locust was an open invitation for the Locust Bug.

The main downsides that I see to mixing species other than black locust is cost and ease of establishment.  Black locust behaves like a true pioneer species and will tolerate root competition from herbaceous competition better than most other hardwoods species.  Seedlings are also generally less expensive than other species.  

Thanks for that insight.  Yes, I mis-typed the 900/acre.  I apologize.

I am currently converting 18.8 acres of pasture into a "test bed" of Silvopasture for my farm.  While it is too late for this project, your ideas on the plantation style implementation have really started me thinking that it might be even easier conversion to Silvopasture from existing pasture (if it will require less than 3 years in Shenandoah Valley of VA).

Thanks again.



Brett Chedzoy said:

My original post suggests about 700 trees per acre.  This would be approximately 8x8 spacing, though I think that other spacings, trees per acre and configurations (e.g. narrow and wide rows, clumps, etc.) could work.  Goal would be to allow enough space between trees so that they'll continue growing "well" for the first 10-15 years until the first "commercial" thinning for posts - vs. having to do a "pre-commercial" thinning (before smaller trees reach minimum post diameter) in order to maintain acceptable growth rates.  Just how long that will take will depend on various factors like site quality, initial care of the plantation, and location (i.e. Maryland vs. Maine).

I think that mixing other species into the planting like honey locust could offer a number of important advantages, not least of which are reducing the risk of pest issues.  Charlie Feldhake at the ARS lab in Beaver, WV found that planting pure groups of honey locust or black locust was an open invitation for the Locust Bug.

The main downsides that I see to mixing species other than black locust is cost and ease of establishment.  Black locust behaves like a true pioneer species and will tolerate root competition from herbaceous competition better than most other hardwoods species.  Seedlings are also generally less expensive than other species.  

Thanks for this guys!

Some photos below of different experiments around our farm on growing black locust.  The first is of a 4.5 acre mixed black locust/black walnut plantation that we established in 1988.  Not much site prep or care was done, plus there was a gypsy moth outbreak, so the locust did better than the walnut - but there are still nice walnuts mixed throughout.  Unfortunately, many show signs of Nectria canker, and the larger native walnuts nearby are also suffering from Anthracnose.  Teachable moment: diversify planting because we don't know what the next serious pest or disease will be.

This ~ 25 year old plantation has been thinned three times over the past 8 years, removing about 300 posts per acre (all of which were used here on the farm).  Using a stumpage value of $5/post, that's about $1500 per acre in net revenue.  The plantation is in need of another thinning to maintain sunlight levels and tree growth, but I try not to cut locust posts until we're within a few months of using them - easier to drive staples in a green post and less likely to split when pounded.

A better picture below showing the diameters of some of the trees - some are approaching small sawtimber diameters.  Note the smaller trees marked in blue - the next to be thinned.

Black Locust is relatively easy to direct-seed.  Trick is to get the seed properly prepared with a hot water soak to soften the hard seed coat, then sow in late-May during "bad haying weather" (10 day forecast of warm, humid weather).  Below is a picture of direct-seeded single rows of locust along our single-strand ht wire paddock subdivision fences.  We strip spray in the fall, then use our 3-pt hitch tree planter to create a shallow furrow and sow the seed by hand.  The young locust are fenced out on both sides (one side with the ht wire, the other with a temporary polytwine fence).  Cattle can graze in a bit from both sides, but not quite reach the young locust. 

This picture was taken in the fall, so there's a lot of aster and golden rod in this pasture (the symptoms of haying this field for many years, before finally turning it into pasture).  Nonetheless, the young locust are alive and well (picture below) and should be well above the weeds by the end of this year. 

The plan for these single rows of locust is to let them get up to a safe browse-resistant height (10 feet?) and then remove the temp fence.  The cattle will undoubtedly damage some of the trees, but with daily paddock shifts and roughly 10 weeks of rest and recovery between grazings (we have 75 permanent paddocks on the farm, and counting), the locust should gradually spread via root suckers and create more extensive silvopasture conditions.  This is an experiment to create silvopastures on the cheap.

Some pictures below of older locust plantations on the farm that have been clearcut and are creeping outward across fences and into adjacent open pastures.  The dead trees were locust that were too crooked to make fence posts, so they were girdled and left standing

I love BL for the reasons you've stated and am really excited about the potential of diversified stands with grazing underneath.

A couple of questions. Will the livestock eat the young suckers? Do you manage the resprouts to be the next trees in the paddocks (after thinning)? Are you doing any selection for the black locust i.e. straighter for better timber quality?

As everyone reading this probably already knows, there's quite a bit of literature out there that reports black locust as (potentially) toxic to livestock.  I have no doubt that too much of most plants under the right (or "wrong") conditions can result in toxicity issues, so experiment with caution!  With that said, we've held our breath and tried some "worst-case" scenarios here on the farm over the past few years - and so far have not experienced any detectable issues.  By worst-case, I mean sheep, goats, cattle, hogs and horses exposed to extensive areas of lush locust suckers and coppice growth at different periods in the growing season.  I will point out though that they have access to plenty of cool-season grasses, forbs and other browse sources at the same time - plus a balanced mineral supplement.  And livestock on our farm are more-or-less continuously exposed to locust and other potentially toxic plants.   That's to say, their digestive systems may be somewhat adjusted to the compounds found in these plants - and we don't unintentionally set the animals up to gorge themselves on something exotic.  A picture below of our goats working-over some advanced locust suckers where the "better" stems have now surpassed the browsing height of the goats.

In the above picture, we were trying to move the goats through the area quickly to selectively thin-out the shorter sprouts.  Key is to move the animals before they start to debark, trample or bend over too many of the larger, "better" stems.

 

Received the following email this morning:  "I remember hearing a
while back that if you girdle locust in mid-summer and let it stand for a year
(or two?) that they don't send up root suckers because they keep attempting to
send energy to their leaves from their roots. I'm just wondering if you can
confirm this? If it's not true, do you know any effective method at controlling
the spread of suckers once black locust is cut (besides grazing, herbicide, or
continuous cutting)? "

I've heard over the years that the suckering response in locust varies by time of the year that the trees are cut, but have never really had a chance to compare it on our farm.  I suspect that locust suckers some regardless of the time of the year that it's cut, and whether it's girdled or felled.  The picture below shows a small plantation where we harvested the straighter trees for fence posts about 2 years ago, and girdled the remaining trees that were too crooked (note to self: use better quality genetics next time).  Most of the sprouts are coppice, originating from the main trunk below the girdle.  But some suckers stemming from the roots can also be seen in the picture.  There would probably be more evidence of suckering, but the area was grazed repeatedly and the suckers took a beating.

The next picture was taken of suckers in an adjacent paddock.  These suckers started to appear prior to harvesting the parent trees, and have survived the repeated grazings.

Unfortunately, I don't remember just when we cut and girdled the locust, but I think it was in the spring around leaf-out.

To answer the question above about other methods of controlling suckering (other than heavy grazing, mowing or poisoning), the only other thing I could think of that MIGHT work is to try to smother the site with a tall, aggressive cover crop like sorghum sudan grass or millet.  But the success of that approach would depend largely on the ability to get a good stand of the cover crop established (good seed/soil contact).

 

Nice webinar today Brett.

I've been planting Black and Honey Locust this spring & I'm have much greater success with HL. I'm treating with hot water (about 190°) and planting the seeds that swell. Some are going in the ground & some in pots.

Any other tricks to get BL to germinate?

The recommended treatment is a "hot water soak": Put seed in container, fill with hot tap water, and let stand ~ 24 hours (overnight is usually sufficient.  If that doesn't work, there are additional suggestions at: https://sheffields.com/seed_genus_species_lot/Robinia/pseudoacacia  

Brett,  Can you please direct me to how I can watch the webinar as I was not able to attend it today.

Thanks

Jim

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