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:
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!
Thanks for all your great articles,
Brett Chedzoy said:
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
Copied below is a recent exchange with Prof. John Fike at Virginia Tech. It points out another important consideration when selecting tree and shrub species to plant in silvopastures: toxicity
I'm seeing some interested in black locust-based silvopastures and I have been
suggesting producers look at BL. However, I recently ran across a "Plants that are Poisonous to Livestock
Video Series" on the http://www.georgiaforages.com/
website - the youtube link is https://www.youtube.com/watch?v=vQJJcaqsZl0
- and I'm wondering if you've seen any problems with this. I had never heard of this as an issue. - John
I always caution audiences not to ignore the potential plant toxicity issues that are reported in literature and anecdotally – but not to live in fear of them either. I think the situations are relatively rare, and that there are usually other predisposing factors involved (not least of which are poor animal husbandry and grazing management). Many of the issues can be avoided by not forcing or incentivizing animals to each too much of something with potentially toxic compounds. An example would be to abruptly turn livestock into lush locust suckers with little other browse and forage available. First, they’re going to crave and gorge on the locust foliage because it’s something novel and very palatable. But the other compounding factor is that they don’t have adequate access to other food sources to dilute, bind and balance the condensed tannins in the locust.
If you watch how most livestock graze, they’ll often head right over to nibble on the browse and tall weeds (most of which are on the poisonous plants list for our area) when turned into a fresh paddock. But after a few minutes of sampling the appetizers, they turn their attention back to the main course (the pasture). There’s something in those plants that they like or that their little pea brains tell them that they need. But once they’ve had enough, they seem to know to switch to eating more traditional stuff.
I can send you dozens of pictures of our animals browsing lush locust foliage. No issues as of yet. Not to say there couldn’t be some in the future.
One word of caution related to this is to consider IPM issues for creating relatively pure black locust silvopastures. Locust leaf miner is starting to show up even here in central NY – a pest that we used to think couldn’t make it north of I-80. Locust borer can also be quite destructive in young plantings (especially if there’s a lot of golden rod – the alternate food source for the miners). I would recommend that folks try to plant a mixtures of species.
A recent email conversation pasted below from a retired extension friend. Some good information on clonal propagation...
Several years back a few of us started collecting and propagating selected strains of black locust starting with the Steiner group from the USDA Big Flats Plant Materials Center with the help of Martin and Shawnna. Peter Smallidge, Cornell Extension Forester also was able to procure seed from a Hungarian black locust orchard...the trees in the orchard had been selected for form, vigor and tolerance to less than ideal growing conditions...the result of 2 selection cycles. Martin/Shawnna still have some of that seed; contact them if you would like to make good use of a small amount of it. Akiva has the best planting of all the collected material.
Spring crept up quickly and it is time to take root cuttings for those who would like to try clonal propagation, the only way to be sure you know what you are getting. Follow out roots from the flares at the base of locust trunks. Carefully pull the soil away from the roots; you are looking for roots that are roughly 1/2-inch in diameter. Use pruning shears to cut as long a section of root as you wish. Cut the end towards the trunk with a flush cut; the root end with an angled cut. Wrap the cut sections of root in wet burlap or equivalent. Ultimately you will plant a root cutting that is about 4 to 6-inches in length; trunk side up...we have been planting flush with the soil layer in a well-drained potting mix. Fungus gnats can be a big problem in greenhouse situations; don't over water...this promotes fungus gnat development. Fungus gnats should not be a problem in outdoor settings because of natural predators.
Collect some of the soil near the roots to mix in the planting pots/area to foster nitrogen-fixing bacterial inoculation of the new seedlings. Not sure if this works, best idea at present...input from the group about this appreciated.
I ran across several papers online though I didn't bookmark that discussed experiments with rhizosphere organisms: bacteria of several species that formed the symbiotic nitrogen-fixing associations and mycorrhizal associations. Bottom line was that the authors concluded that these rhizobial associations had a significant affect on the growth and vigor of the trees they were associated with. So given that, how valuable is collection of soil near superior trees to the propagation of future locust groves? I wish I knew more about tree genetics and rhizosphere organism influence on black locust growth and vigor.
Projects with black locust: Identify superior clones based on form, vigor, resistance to locust borer/lack of damage...propagate them and plant in orchards for cross pollination and eventual seed collection, future selection, etc.; experiment with mixtures with other hardwoods to enhance locust growth and protect against unforeseen pests (in the excellent publication "U.S. Department of Agriculture, Farmers' Bulletin No. 1628 Growing Black Locust Trees ((available online or used thru Amazon)) they suggest mixtures with sugar maple, white ash, red oak and black walnut. Sugar maple since it leafs out early should be a good choice to help keep invasives at bay; black walnut mixes should probably include either sugar maple or red oak or other hardwood species that shade the ground better than locust/walnut???).
When I've visited different black locust groves I've noticed differences in the form of the trees, how well they heal where limbs once were, trunk flares and depth of bark furrows. In the wood you find some that is straight grained and solid, and other pieces with curvy grain and significant cracks. I'm guessing that some of these defects (deep furrows are one to avoid) can be avoided through superior tree selection, good site selection and preparation, rhizosphere inoculation?, use of mixtures?, etc. Tom Brown, Locust Lumber Company in Newfield, NY has observed less locust borer damage when the locust trunks were covered (shaded, lower temperature) by vines; we think what he is seeing are Virginia creeper vines.
Anyway there's a bit on black locust for those who are interested in this native, fast growing, very rot resistant and strong hardwood species. Please add to the above with your own observations and experience.
G'day Brett (and others):
Thank you for hosting this excellent discussion! Can you recommend where I might source superior planting materials for establishing a silvopasture? Do you know of any seed sources from improved cultivars, apart from the seed stands in Hungary? Is there any path to importing the improved Hungarian seed? Can clones be propagated effectively via tissue culture?
So many questions - just trying to figure out a strategy to secure the planting material for a silvopasture startup.
I recently wrote an article about Angus Glen Farm, Brett's silvopasture operation. The text focuses on the potential of black locust and its financial viability.
Save the date everyone for "Growing Black Locust as a Timber Cash Crop in the Northeast" -
A special one day conference to explore the methods and potential for cultivating Black Locust (Robinia pseudoacacia) profitably and successfully
Friday, October 20th, 2017 at the Big Flats PMC, Big Flats, NY (~10:00 – 4:30)
Details coming soon on the events page of the forum