Eliminating Invasive Buckthorn With Goats, An Ecological and Habitat Restoration Study

Final Report for FNC08-737

Project Type: Farmer/Rancher
Funds awarded in 2008: $1,873.00
Projected End Date: 12/31/2010
Region: North Central
State: Wisconsin
Project Coordinator:
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Project Information


Operation Areas:
Fossil Ridge Farm
Burlington, WI
Owner - Robert, Marie and Kimberly Hunter

Fossil Ridge Farm is the home base for The Green Goats, my target grazing service. The farm consists of a house and several sheds on six and a half hilly acres - mostly mixed grass, weedy pastures with some woods along old fence lines. Wooded sections are mostly black cherry, a few oak and a thick understory of invasive woody vegetation.

Major invasives include: buckthorn, honeysuckle, thistles, curly dock, burdock, and tansy.

Some native flowers were already present on the site and others have been seeded in around the house.

Additional study areas included:

Two acre Buckthorn Infested Backyard
Salem, WI
Owner - Frank and Martha Slifka

155 acre Waterford Hobby Farm
Waterford, WI
Owner Robert and Susan Depree

Pringle Nature Center, Bristol Woods
Bristol, WI
Owner - Kenosha County Parks and Pringle Nature Center

Two acre Trevor Backyard
Trevor, WI
Owner - Anonymous

24 acre Abandoned Apple Orchard/Pony Farm
Bassett, WI
Owner - John and Louise Franz

Rotation grazing of geese, goats and horses. Free range Muscovy ducks provide some insect control. Use of horses to spread manure over bare, gravel/clay ground. Use of confined horses to trample young invasive woody plants and thistles. Use of geese to mow yard (kind of messy but they do nice work).


Goals: One of my main goals was to determine the time it takes for a specific number of goats to defoliate invasive brush, concentrating on buckthorn.

A secondary goal was to determine how long it would take the defoliated brush to re-grow leaves.

The third goal was to create a strategy for using goats to remove brush and restore native or pasture habitat, concentrating on a rotation grazing method that could be used as a basis for creating a target grazing business rather than a constant exposure method that could be used on any farm where the goats live full time.

The study was very simple. I built pens approximately thirty feet by sixty feet in areas of heavy buckthorn brush infestation. I introduced a group of goats into each pen at one week intervals. So, if goats went into Pen Number 1 on a Monday, they would go into Pen Number 2 the following Monday. Pen Number 3 the Monday after that and so on.

I had two types of vegetation in separate study pens. The first type was uncut invasive buckthorn. The second type had the buckthorn cut to the ground and allowed to re-grow before the goats were introduced. Although I ran one grazing cycle through the pens in 2009, this data refers to the summer of 2010.

I started the study in the uncut pens. One mature Spanish buck and three yearling Spanish and Spanish cross bucks were introduced into Pen Number 1 on June 13, 2010. At first I was reluctant to leave the goats overnight. It was their first time being confined by three strands of electric string/wire instead of an electric net fence. By the second week I was leaving them overnight.

Pen Number 1

June 13 - Bucks in 1:30pm to 8pm. - Consumed about half the vegetation.
June 14 - Bucks back in 4:30pm to 8:30 pm - Pen Number 1 defoliated

Pen Number 2

June 20 - Bucks in to Pen Number 2 at 9:30
June 22 - Bucks out of Pen Number 2 at 8:30 am - defoliated

Pen Number 3

June 27 - Bucks in to Pen Number 3 at 12:15 pm - defoliated
June 29 - Bucks out of Pen Number 3 at 3:00 pm

Pen Number 4

July 4 - Bucks into Pen Number 4 at 12:00 pm
July 5 - Bucks out of Pen Number 4 at 6:00 pm - mostly defoliated, left some low stuff

After the initial grazing, goats were re-introduced into the pens as the foliage re-grew enough to feed them. Since this is a subjective observation, the time intervals varied and were also affected by other obligations on my part that favored moving goats on one day over another.

Pen Number 1

July 9 - Bucks into Pen Number 1 at 2:00 pm and out at 6:30 pm - goats laying down chewing
cuds when removed and probably finished grazing pen in two or three hours.

Pen Number 2

July 19 - Bucks into Pen Number 2 at 1:45 pm and out at 6:00 pm

Pen Number 3

July 25 - Bucks to Pen Number 3 at 9:00 am and out at 5:30 pm

Pen Number 4

August 4 - Bucks in to Pen Number 4 at 11:40 am and out at 5:00 pm – 90 percent defoliated

Note: Grazing after this date will produce little or no regeneration of leaves or sprouts until the following growing season.

Pen Number 1

September 5 – Bucks in at 10:45 am and out at 1:15 pm

Pen Number 2

September – Bucks in at 1:00 pm and out at 3:00 pm

Pen Number 3

October – Bucks in at 9:50 am and out at 2:00 pm

Pen Number 4

October 12 – Bucks in at 12:00 pm and out at 3:30 pm

Strategy Number 2

For this second part of the study I cut brush down, let it grow back then grazed it. It is the fastest way to clear the brush but it is also the most labor intensive.

Because my fencing skills are rather poor, creating identical study pens on the steep hillsides that I was allowed to cut was too difficult. Instead, I built one big, oval pen about 300 feet around in my original study area and made observations at several other farms where my goats were working. Because the brush leafed out before I could cut it, I ran the goats through to thin it and make my job easier.
After one grazing, brush was cut in July and allowed to grown back until the end of the growing season. Regenerated growth was about knee high at this time. The bucks were introduced and the pen was cleared in about two days.

Observations at other sites:

Buckthorn was cut at different times on degraded oak savannas on two hobby farms with abundant moisture and rich soil, and on two residences with steep, rocky, yellow clay soil.

In March of 2010 forest undergrowth was cleared from several acres using mechanical cutters that left stumps up to ten inches high. By July 2010 the re-growth had formed an impenetrable mass ranging from seven feet high in the wetter areas to about three feet high on the hillsides. Species consisted of mainly buckthorn, especially near the ponds and prickly ash (nature’s razor wire) on the hills. Honeysuckle, multiflora rose, and wild grape were also present in annoying quantities.

The Wether Underground consisting of William Ayers, a mature Nubian wether and ten yearling Spanish wethers entered this area of approximately 1.5 acres on July 12th. Two small does and three kids joined them a week later. By July 28th the area was sufficiently defoliated. Re-growth followed the same four to six week pattern that I observed in the other grazing pens. Unfortunately the goats were unable to re-graze this area.

In summer and fall of 2009 the goats grazed buckthorn in an apple orchard abandoned for about twenty years. After grazing; buckthorn, box elder and other weed tree species were cut down, leaving waist high stumps. This area was left to grow until early October 2010. Re-sprouts varies from about two feet of new multiple stems and thick leaves on the buckthorn to seven foot long, new branches on the box elders. A herd of thirty-five does and their three month old doelings grazed out a half acre of heavy brush in about two days. An attempt to remove the deadwood will be made this year.

Buckthorn cut flush with the ground on dry hillsides re-grew to about a foot tall of new multi-stems in just over a month. Buckthorn whips cut flush with the ground and then burned over in August 2010 re-grew into tiny multi-stemmed shrubs about six inches tall in just over a month.
It appears that cut buckthorn will regenerate later in the year than grazed buckthorn. The short duration of these observations (over only two growing seasons) may account for this difference. Some buckthorn saplings cut beneath deep shade to provide end of season feed for goats did not regenerate the following year.

As a feed source, buckthorn greens up early in Spring and stays green longer than most other trees or shrubs in Fall. Edible leaves have been observed in southern Wisconsin on buckthorn from mid-April through the end of November.


I discovered the time it takes to defoliate a specific amount of invasive buckthorn with a few goats and how long it takes the buckthorn to recover.

In general, for any amount of buckthorn, for any number of goats: If it takes two to three days for the goats to defoliate the area the first time, it will take them three to five hours to defoliate it on subsequent grazings spaced about four to six weeks apart.

The study did not last long enough to determine the number of grazings to kill a buckthorn tree but observations on my farm show some seedlings can be killed in one grazing and larger trees will usually take at least two years of grazing two or more times per season to die. Bark stripping, which occurs mostly in winter, will kill the tree tops in one season, eliminating the need for immediate cutting. Regeneration of shoots from the still living roots provides a greatly reduced biomass that is all within the reach of the goats.

The amount of time it takes for cut buckthorn to regenerate shoots is about a month, same as for grazing. The rate these shoots grow and the biomass produced is dependent on the size of the tree cut, the food reserves in the roots available to regenerate shoots, and the amount of light and water available after cutting. Shoots on dry hillside may take all summer to get knee high whereas shoots (first cut during dormancy in March) on rich soil near lakes can grow over six feet by mid July.

The advantage to cutting is the immediate removal of the buckthorn canopy. Disadvantages include the amount of human work involved and the sudden amount of light hitting the area previously shaded by the canopy. Observations of fallen oak trees show this light will cause a carpet of buckthorn seedlings to sprout over the next few years. Unless a control, such as grazing goats, is in place, cutting alone could make the problem worse.

Advantages to grazing in uncut buckthorn infestations are the reduced time and labor costs and the built in shelter the brush provides the goats.

Disadvantages are the ability of the trees to survive the grazing because a significant part of their leaves are out of reach of the goats. Bark chewing can kill the tree tops but won’t necessarily happen unless goats are kept in the area a significant amount of time. Also - the increased time it takes to completely remove the buckthorn (letting it die and decay where it stands).

A combination strategy is possible – grazing the buckthorn in uncut stands, providing hay after defoliation to encourage bark chewing while cutting trees a few at a time to give goats access to leaves. This strategy may be easier to fit into daily farm work but more difficult to use for paid grazing work.

Failure to control buckthorn and other weeds can happen if goats are not stocked in sufficient numbers or not confined long enough on a grazing paddock to stress the plants. The plants must be overgrazed and re-grazed before they can recover to damage them enough for control or eradication.

Current systems used by the Wisconsin DNR and US Fish and Wildlife Service to clear brush involve mechanical cutting using chainsaws, brush hogs, and large cutting blades on movable arms that leave the forest with splinted, knee-high stumps, looking like it was attacked by Godzilla. Cutting is followed by poisoning stumps or spraying of areas with herbicide to restore grassland species. These same practices are used by private landscape companies. Chemicals such as glyphosate and triclophyr are often mixed with diesel fuel before application. These practices pollute the land, run off into the water and are destructive to small ground dwelling animals like toads, ground-nesting birds, fish and insects. Diesel fuel contains known carcinogens including benzene. The noise, fumes and disturbances are also detrimental to any wildlife species sensitive to human intrusion. Any repetition over the years could result in a buildup of non-degradable toxins in the environment. Poisons do not always kill completely and plants develop immunity over time. Poisons do not address the ecosystem imbalances that allowed the buckthorn infestation in the first place.

Goats take longer to achieve the eye-catching results of poisons but they do so by restoring the ecological balance to the system without harming native animals. Unlike poisons, goats improve the soil with their manure and can trample native grass seeds or cover crop seeds into the soil. Poisons treat a symptom of an environment out of balance. Goats restore the balance, healing the landscape, one bite at a time.

I was able to create strategies for clearing or controlling the spread of buckthorn and other woody invasive plants by using goats alone or as a follow up to mechanical cutting. This allows me to turn my goat herd and knowledge into a marketable service.

Advantages: Provides low cost brush control for farmers who own herds and another source of farm income from raising and/or renting out goats.

Disadvantages: Livestock needs can tie you down and there are expenses involved with keeping animals when they aren’t eating brush.

Examine your needs for weed and brush control and create a grazing plan that balances the amount of work you can do with the amount of time you have to clear the brush.

Here is an email I sent to US Fish and Wildlife to explain how the goats work:

Thanks for your inquiry about the goats.

When it comes to restoration of prairies, savannas and woodlands, I think targeted goat grazing is the best long-term solution. They work by shifting the ecological balance to favor the native trees and grasses common in oak savannas.

Goats prefer to eat woody plants, favoring buckthorn, multiflora rose and honeysuckle over young oak or hickory. Second choice is broad leaved plants like thistle, burdock, and curly dock. Last on the list is grass and hay crops like alfalfa and clover. They will eat native flowers and some native seedlings. I handle this by targeting the graze to avoid the critical growing times for these plants or putting a temporary protective fence around the native plant.

They kill targeted plants by removing the leaves (and sometimes the bark) and starving the roots. A large root with plenty of nutrients will regenerate faster, heavier and more times than a smaller plant on poor soil. It takes at least 4 weeks for buckthorn to recover enough to justify a second grazing.

I conducted a study (funded by S.A.R.E.) over the last two summers. I placed 4 goats in 30x60 foot pens with a fairly heavy buckthorn thicket. Stems were mostly thumb and broom handle sized, with some larger tree sized buckthorns. There were also oaks, poplars, and box elder trees. Native trees were mostly mature with a few trunks 3 to 4 inches across. The goats left all these trees, except the leaves on the box elders, alone.

Goats were introduced at one week intervals and entered pen Number 1 again 4 weeks after it was first grazed. It took the goats 3 to 4 days to clear the pens (as high as they could reach) the first time and 4 to 5 hours the second time. This timing was consistent whether the goats grazed untouched buckthorn or buckthorn that had been cut and allowed to re-grow.

Goats can be used without any cutting as long as the buckthorn stand is young enough for them to reach all the leaves on the targeted plants. If the stems are small enough, the goats will stand up and bend them down. When one goat does this, the others mob in and strip the plant bare. They are very greedy eaters. Using this method, goats can strip stems up to 10 or 12 feet tall.

For 20 acres: Assuming, for demonstration purposes, I can split the acreage into 10, 2-acre paddocks - I would introduce goats into the first paddock. Let's say it takes them 5 days to clear it. They go on to paddock 2, 3, 4, 5, and 6. That's 30 days (about 4 weeks) to graze 6 paddocks once. At this point I've cleared 12 acres but the first 2 acres have grown back enough to justify a second graze.

So the goats go back to paddock Number 1 for a second graze. They clear it in 10 to 24 hours. Then they enter paddock Number 7 for 5 days. By this time paddock Number 2 is ready for a one-day second graze. Paddock Number 3 is not ready for a second graze so, after 24 hours, the goats go on to paddock Number 8 and so on. Each time the paddock is grazed, the buckthorn, etc. bounces back with fewer leaves. So it takes less and less time to strip the paddocks. Once all 10 paddocks have been grazed once, I start combining paddocks for the subsequent grazing. In this way, the plants go through an entire growing season under heavy grazing stress with little or no chance to build root reserves for the winter.

The goats will graze other plants along with the invasive woodies. They will also make bedding areas that can leave bare ground. Use this to spread seeds of cover crops or native grasses. The goats will trample the seed into the ground, increasing the soil to seed contact and increasing successful germination. Increasing competition at the same time you increase predation on the invasive plants, will restore the native communities faster, and with less energy and expense.

A few more things to think about:

The time it takes to clear a paddock depends on the biomass of the grazable plants and the number of goats I introduce.

Comparing goats to chemicals: First, there is the environmental damage, especially to amphibians and forest floor critters, when using a broad spray. Painting stumps reduces the amount of chemical but you will miss every tree seedling too small to see. Then you'll be doing it again next year. Many outdoor enthusiasts expect their public lands to be poison free for the safety of their dogs and children.

Seed bank is a big issue. What is the vegetation mix in the areas you cut? Will a thousand buckthorn seeds germinate now that you've opened the canopy? Will garlic mustard expand, suppressing the germination of native seeds? Goats eat garlic mustard and can strip those itty-bitty buckthorn whips to nothing. With their immature root systems, one grazing might kill them.

Goats work 24/7 without benefits.

April 2009 - Networked at Earth Day Kenosha celebration where I met Wisconsin Senator Robert Wirch. He offered his full support for the goats. I also made contact with Barry Thomas, board member at the Pringle Nature Center (located on 200 acres of buckthorn infested county parkland).

Summer 2009 - Article featuring my goats, including SARE info, appears in Kenosha News.

Summer 2009 - Gave goat talk and demo at Pringle Nature Center.

September 2009 - Took goat herd to Pringle Nature Center for two week target grazing demonstration (it was supposed to be 3 weeks but they ran out of brush!). Have been asked back for 2010.

October 2009 - Left my name and number with Kenosha County Extension, offering to speak to 4-H kids about goats and target grazing.

October 2009 - Hosted 4 scientists from The Chicago Botanic Garden. Took them on tour of all the places my goats had been grazing on private farms and public parks. They were thrilled and want to conduct their own target grazing goat study on 100 acres of buckthorn infested land the Botanic Garden owns. Note: With all their resources, they have not been able to get their buckthorn under control on any of the infested acreage.

Posted information on my web site.

November 2009 –Farmers Forum at National Small Farm Trade Show and Conference in Columbia, Missouri.

January 2010 - Networked at Annie’s Project classes for farm women at UW Madison.

March 2010 - Article about The Green Goats will come out in local veterinarian’s newsletter.

November 2010 – Farmers Forum at National Small Farm Trade Show and Conference in Columbia, Missouri

November 2010 – Networked at second Annie’s Project class in Elkhorn, WI

November 2010 – Interviewed on National Public Radio - wuwm.com/media/news/news_112910135838.mp3

February 2011 – Passed out info sheets at the Wisconsin South East Grazers Network Annual meeting

It would be nice to have more than one deadline each year to reduce the amount of time between the initial idea for a project and potential funding.


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.