| PDF (13 MB) of Power Point presentation on buckthorn eradication (given at IPAW meeting in Milwaukee in Dec. 2011)
When restoration work began at what is now Pleasant Valley
Conservancy, the area was heavily infested with undesirable
woody vegetation, both brush and trees. The original savanna oaks
and hickories were still there, with their open-grown character
visible, but surrounded and crowded with "bad" woody
plants. The invaders were all fire-sensitive and had encroached
during the 50 or so years since the last burns.
Early attempts to knock back the invasive woody plants by
fire were unsuccessful, as there was insufficient fuel on
the ground. In retrospect, fire should not have been used
at that stage anyway, since all it would do was top-kill the
woody plants, but not eradicate them. They would resprout
from dormant buds and a bigger mess would be created. We were
thus "lucky" that fire did not work.
Herbicides for weed control
Herbicides play a central role in restoration ecology, but they must be used carefully and with full knowledge of their potential activities. Each herbicide sold comes with a label that provides essential information about the chemical, its activity, and precautions that must be taken when using it. It is mandatory that before using any herbicide its label must be read and understood.
Uses of herbicides for specific weeds and woody plants are given below and on other pages of this web site. This link provides a summary of the main herbicides used at Pleasant Valley Conservancy.
The correct approach to removal of woody invasives:
- Cut and treat with an appropriate herbicide
- Introduce fire
- Introduce understory grasses and forbs suitable to a savanna
- Burn yearly to keep invaders in check
- Continue to monitor and control woody invaders, both shrubs and trees, which grow from the seed bank and/or dormant rootstock
Cutting woody plants: sprouters and nonsprouters
When cutting a tree or shrub, it is important to know whether it is a sprouter or nonsprouter. If it is a sprouter, then the cut stump must be treated with herbicide to prevent resprouting.
All shrubs are sprouters.
They have dormant buds in both the stem and in the root collar. If a shrub is cut below the lowest stem bud, it will sprout from one of the root collar buds. If cut higher, then resprouting will occur from the first dormant bud below the cut. In either case, to prevent resprouting, it is essential that the cut stem be treated with herbicide.
Trees may be either sprouters or nonsprouters
Trees that are nonsprouters
Conifers (softwood plants; whose leaves are needles) such as pines, red or white cedar, spruce, etc. The stumps of these trees do not need to be treated with herbicide.
Trees that are sprouters
Sprouters are all the hardwoods (broad-leaved plants) that will be encountered during a restoration project. These include black walnut, slippery elm, box elder, black cherry, basswood, hackberry, and any of the oaks.
Aspens are sprouters, but are a special case. They must be dealt with by girdling.
Herbicide treatment of cut stumps
The stumps of shrubs and trees that sprout should be treated with an 15-20% solution of the herbicide triclopyr dissolved in an oil such as bark oil, diesel, or kerosene. Trademarks of triclopyr include Garlon, Access, Crossbow, etc.
There are two types of triclopyr, one is a butoxyethyl ester soluble in oil and the other is a triethylamine salt soluble in water. It is the oil-soluble type that should be used for cut stump treatment. For small trees, the whole stump should be treated, whereas for large trees just the outer region, including the cambium layer, needs to be treated. An oil-soluble red or blue dye should be added to aid in following where the herbicide goes. (See photo) (Pathfinder is the trade name of a Garlon 4 product that is pre-diluted in oil and is ready to use.)
Black oak stumps that have been treated with Garlon 4 (in oil) to prevent resprouting. The blue dye shows where the herbicide was applied. Only the outer layer of the log, which includes the cambium layer, needs to be treated.
These two black oaks were removed because they were crowding an adjacent open-grown bur oak.
Clearing of both oak savannas and prairie remnants
involves a lot of chain saw and brush cutter work. This work can be done by the landowner, or it can be contracted out to a contractor skilled in restoration ecology. A commercial logger is NOT recommended, because such a company cannot be relied upon to cut wood without damaging the habitat. (Commercial loggers may propose a substantial remuneration. This tempting offer should be resisted. If finances do not permit hiring a restoration company for the whole job at once, then a smaller restoration unit should be used, and the work spread out over a number of years.)
For small projects, part-time workers can be hired, but for major projects a contractor who specializes in restoration work should be used. If volunteers are available, they should have experience with tree cutting and should be required to wear appropriate safety equipment (chaps, hard hat, goggles, ear protection, etc.), although unskilled volunteers can be used to help with burning brush piles and treating cut stumps.
For oak savanna restoration, all trees that were not part
of the original fire-dependent ecosystem should be removed. If resources are not available for a complete removal, special attention should be given to trees that are crowding open-grown bur or white oaks. A few oaks may also need to be removed. Black or red oaks are rapidly growing trees that often grow into the crowns of savanna oaks. If they are crowding white or bur oaks they should be removed. Other tree species to remove in an savanna restoration include elm, black walnut, cherry,
basswood, maple, and box elder. Some shagback hickories might also be removed, although
a hickory standing by itself can be left.
Woody shrubs should be removed at the same time the trees are
cut. Woody shrubs include buckthorn, honeysuckle,
gray dogwood, sumac, black cherry, and prickly ash. Although some of these shrubs are native, they are often rather invasive, especially in the increased light provided by the clearing process. The cut stumps of woody shrubs should be treated with herbicide at the same time the tree stumps are treated.
The good wood generated in the clearing process should be salvaged, for
use as either fire wood or as lumber.
However, heavy equipment should not used to remove logs, since it may damage the roots of trees being retained. Wood suitable for firewood can be cut into short pieces and removed with a pick-up truck. Excess wood can be left at the side of a road, where local residents will quickly
remove it. If off-road driving is required, this should only be done in the winter (at snow-free
times), and care taken to avoid making ruts. Frequent
off-road driving over the same track should be avoided. Growth of
savanna plants the following season will quickly hide whatever ruts
remain. Logs suitable for the saw mill can be skidded over snow to a nearby road in the winter.
Brush that is cut should be stacked into large piles, together
with the smaller limbs of the trees, and burned in the winter when snow is present. The number of burn piles should be kept to a minimum.
As much as possible, dead trees can be left standing as habitat
for woodpeckers and other wildlife. Such dead trees sometimes
presented problems during controlled burns, but this risk
is acceptable in the interest of creating desirable wildlife
Aspen cannot be simply cut like other tree species, but must
be girdled. Details are given below.
An Example: Clearing Savanna Areas at Pleasant Valley Conservancy
The lower part of the south-slope, which was predominantly
prairie, was cleared first, and the upper slopes and ridge
top, which were savanna, were cleared later. This was primarily
a budgetary decision. It was less expensive to clear the south
slope because there were fewer undersirable trees and removal
of the cut material from the hill was relatively easy. Although
cutting trees on the ridge-top savanna was easier for the
workers, because it was on more level ground, removal of cut
material was more difficult and expensive.
The slower pace of savanna clearing was also necessitated
by the need to have seeds to plant in the cleared areas. Since
we were trying to use only local seeds, we had to phase in
the clearing with the seed collecting possibilities. In general,
around 10-15 acres of savanna were cleared in a single winter.
The schedule of clearing is shown on the table below.
Although most of the cost of the prairie and savanna clearing
was paid for by Savanna Oak Foundation, Inc., two helpful
grants were obtained from federal agencies. The Wildlife Habitat
Incentive Program of the U.S. Department of Agriculture provided
a grant for the work in 1999 and 2000. The Private Lands program
of the U.S. Fish and Wildlife Service provided partial support
for the work carried out in January-March 2003. During the
main period of tree removal, from 2003-2007, all restoration
work was funded by the Savanna Oak Foundation, Inc.
|A partially cleared south-slope hill (Unit 6), November 1999. The brush and small logs were stacked for drying and later burning. Large logs were rolled down the hill to Pleasant Valley Road and cut up for fire wood or saved for lumber. The cedars in view were cut and tossed on the burning piles. Several remnant prairies can be seen. The lower (just above the brush piles) is primarily little bluestem, and a small "goat" prairie is visible at the top of the hill, under the rocks. This latter consists primarily of big bluestem.
|The brush pile shown in the photo above being burned in light snow, January 2000. Drip torch fuel is used to start the fire. In the winter of 1999-2000 over 200 large brush piles such as this were burned on the south-facing slope.
Schedule of Clearing
||Clearing of cedar on goat prairie, unit 1.
||Very few hardwoods here
Clearing of cedar, red pine, and
hardwoods that were not fire-dependent on south-facing
slope (units 2 and 3) Girdling aspen
Clearing brush from a small area of nice savanna white
oaks in Unit 12B. First savanna burn.
Elm, black walnut, box elder.
Aspen girdling is a special case
First purple milkweeds appear in restored area
||Clearing of cedar, red pine, and hardwoods that were
not fire-dependent on south-facing slope (unit 6 and part
||Elm, black walnut, box elder. Partly funded from the
||Clearing of cedar, red pine and hardwoods that were
not fire-dependent at east end of south slope (unit 18).
||Many black walnuts. WHIP grant
||Clearing of black oak and other hardwoods in bur oak
savanna (units 8 and 10).
||Over 100 brush piles burned in winter
||Clearing of black oak and other hardwoods in bur and
white oak savanna (unit 19). Girdle aspen clone
||Over 200 brush piles burned in winter
||Clearing of black oak and other hardwoods in white oak
savanna (units 12A and 12B) Girdle aspen clone
||About 50 brush piles burned in summer 2002
||Clearing of black oak and other hardwoods in white and
bur oak savanna (unit 11) Girdle aspen clone
||Partial FWS cost-sharing
||Complete clearing of unit 11. Clear unit 20 and 21 of
walnut and other undesirable trees. Girdle aspen clone.
Clear unit 13 of buckthorn and other undesirable shrubs.
Complete clearing of Unit 19 to its east end.
||Savanna Oak Foundation funding
||Extensive clearing of marsh edge (below Pleasant Valley
Road) in preparation for wet-mesic/mesic prairie planting
(creation of Crane Prairie). Controlled burns of all savanna
habitats (Nov. 2004 or April 2005).
||Savanna Oak Foundation funding
||Clearing all invasive woody plants from the East Basin
||Savanna Oak, LIP, and WHIP funding
||Outstanding spring burns. Continued work on invasive woody plants, including extensive spring spraying of bramble resprouts. Herbicide treatment of the East Basin (twice) and removal of all girdled (dead) aspen. Extensive seed collection for use in planting the East Basin
||Savanna Oak and WHIP funding
of Aspen by Girdling
There are two species of aspen that
are native to our area: trembling aspen (Populus
tremuloides) and big-tooth aspen (Populus grandidenta).
Conservancy had both species, although trembling aspen
was the more common. We worked hard to get rid of
these trees, and were rewarded for our work by the
discovery that hidden among the
aspens was real prairie sod.
Aspen clone encroaching on a former agricultural field. Within about 50 years the size of the field had been reduced almost in half.
are native trees but remain
undesirable inhabitants of prairies and oak savannas.
are capable of spreading rapidly and crowding out
are pioneer trees on open , burned, or cut-over land. Although important economically
in the paper industry, they are a menace in prairies
and oak savannas and eradicating them became an early
goal of our restoration.
Although aspens grow
from seeds, the primary spread is asexual by underground
runners. The typical aspen "grove" is a multi-stemmed
clone in which all the roots are interconnected. If
an injury to a root occurs, there will be a rapid
response by the clone, and new shoots ("suckers")
will be sent up all over the area. New shoots have
been known to arise as far as 50 feet from the nearest
aspen tree! The clone may expand simultaneously in
several directions, as influenced by environmental
conditions. In western
, huge aspen
clones have been found, the largest occupying over
100 acres. In our part of the country, aspen clones
are smaller, but are often more than an acre in extent.
Aspen clones are widespread
in the Driftless area of southwestern
They are easy to spot in spring when the light green leaves first
appear, and in the fall, when the leaves take on their
distinctive fall color. Virtually every woodlot in
our area has one or more aspen clones. This was not
always the case. In earlier times, aspens were uncommon
in our area. This was because aspens are fire-sensitive,
and when prairie and savanna fires were widespread,
they were held in check.
The first air photo
of Pleasant Valley Conservancy, taken in 1937, shows
that the land was quite open. Fire protection and
elimination of grazing resulted in a major change.
Subsequent air photos showed our land gradually becoming
wooded. Many of the trees were aspen. The air photos from the 1990s show virtually no open
land at all, and our field studies showed that most
of the trees were aspen.
We have identified
many trembling aspen clones, in different parts of
the Conservancy. There was a small clone above unit
1 (the goat prairie), two or three very large clones
in the White Oak Savanna (unit 12A), at least three
clones that surrounded the upper agricultural field
(see photo at top of page) that was later planted
to prairie in 1998 (now called Toby's Prairie). There
was also a large clone at the lower end of the White
Oak Savanna, bordering the ag field that is now the
Pocket Prairie. Also, there were two or three clones
surrounding the ag field that is now the Ridge Prairie.
Small clones were also present in the lower part of
Finally, there was
a clone of big-tooth aspen in Unit 19. This clone
was also invaded with white sweet clover, a persistent
weed that is devilishly difficult to eradicate.
Girdling When looking at a large aspen clone, it may be tempting
to go in with a chain saw and cut it down. Wrong!
The roots remain alive and immediately send up a huge
number of new shoots. An area that had perhaps 5 or
10 large aspen trees will soon have hundreds of aspen
There is only one certain
way of killing aspen and this is by girdling.
means stripping a layer of bark and the underlying
cambium and phloem in a band around the trunk. The phloem vessels translocate sugars and other nutrients
to the roots, so if the phloem tubes are broken, the
roots become starved of food. The xylem vessels, which
translocate water to the leaves, are not affected
by girdling. With girdling, the upper part of the
tree still remains alive, since photosynthesis can
continue. Eventually, however, the roots die, and
the whole tree dies. The first year after girdling,
the clone may appear almost normal, but by the second
year the clone usually dies. The dead trunks can then
be cut without stimulating resprouting.
For girdling to be
affective the whole clone must be treated. It is also
important to make the girdle in such a way that the
underlying xylem is not damaged. Damage to the xylem
sends signals to the tree that something bad has happened,
and the tree then sends up shoots.
The photos below demonstrate
the technique of girdling. Girdling is done in May
or early June when the sap is running fast and the
tree is growing. At that time, the bark can be easily
cut and the girdled bark stripped off. Later in the
summer, it is virtually impossible to do a girdle
We carried out a small
girdling in 1995 and initiated major girdling in 1997.
Our major girdling was done in 1998 and 1999, but
some girdling was done in 2000, 2001, 2002, and 2003.
The trees girdled in 1998 (see photos here) died in
2000 and were cut, stacked, and burned. Almost all
the trees that were girdled are now dead and have
been removed. The dead trees of the major aspen clone
in unit 12B were finally cut and removed in the spring
of 2002. Although we still have many aspens on the
east end of Pleasant Valley Conservancy, aspens in
the highest quality land are now gone.
We did our final aspen
girdling in May 2008 in the area we call the East
Basin (Unit 22). This isolated basin was not cleared
until the winter of 2007-2008. There were close to
100 aspen in this clone, many of them quite large.
The technique for girdling aspen. The tool was made from a truck spring. The tip of the spring was rounded off and one edge sharpened. The curve of the tool makes it easy to encircle the bark. It is important to make sure that the bark is completely broken all the way around the trunk. At least six inches vertically should be separated. It is important that every aspen tree in the clone is girdled.
An unexpected result
of removing the aspens was the discovery that hidden
within one of the clones was real prairie sod. Conservative
species such as Panicum leibergii and Viola
pedatifida had managed to survive within the
clone. Once the aspen were gone, these species (and
others) were able to thrive. Today we can identify
the exact boundaries of this aspen clone from the
"good" species that are now present.
Although girdling is
very effective, small aspen resprouts may still come
up at the edge of girdled areas. These can be handled
by cutting with a hand clippers and treating the cut
stems with glyphosate, and we continue to do this
every year or so.
Cost of Restoration
Restoration work of the kind described here
is expensive. During the largest efforts described in the
table above, the costs ran between $3000 and $5000 per acre.
These costs were for an experienced crew who worked very efficiently,
and includes cutting of trees and brush, stacking and burning,
and all herbicide treatment of cut stems. It does not include
the cost of removal of firewood except where the wood could
be rolled down the hill to the town road.
The specified payment rates (dollars per acre)
that the Federal Government uses in their granting programs
covers only a small part of the operation. For instance, the
per acre payment rate for removal of heavy brush is given
at $190.00 per acre, which is only a small part of the cost.
(Sites with heavy brush have more than 40% of the area stocked
with woody vegetation 0-2 inces in diameter and up to 25 stems
per acre larger than 2 inches in diameter at the ground line.)
Techniques for brush control
The two major techniques for brush control are 1) cut and treat and 2) basal bark. Each method has its appropriate uses.
Cut and treat
Used for large infestations, especially of small brush such as brambles, gray dogwood, small buckthorn, etc. A gasoline-powered brush cutter is used, with a toothed saw blade. The blade is kept very sharp by frequent sharpening in the field. (Sharpen the blade with each new tank of gasoline.)
|Cutting mixed small brush: brambles, buckthorn, gray dogwood, etc. The blade is kept very sharp, level, and close to the ground. Each cut stem is treated with herbicide using the paint stick method.
|Treating cut stems with herbicide, using the paint stick method. The treating crew follows the brush cutter and treats every cut stem. If buckthorn is present, Garlon 4 in oil is necessary, but for gray dogwood, willow, and brambles, glyphosate can be used instead.
|This work can also be done in the winter, provided the snow is not too deep. It is essential to add a dye to the herbicide mixture so that the treatment process can be monitored.
With the basal bark method, cutting is not required. An oil-based herbicide is used (such as Garlon 4), and the herbicide is "painted" up the stem of the woody plant. This technique is used for infestations where the "woodies" are scattered. The herbicide can be applied from a backpack sprayer or spray bottle. If the target is small brush, the paint stick method is used (as shown below), since it permits more precise application of herbicide.
|The paint stick method for basal bark treatment of small buckthorn plants. The herbicide-containing paint stick is swiped up the side of each stem. With stems this small, only one side needs to be treated.
Select an invasive species
Most people involved in restoration of native
landscapes learn quickly about the evils of invasive woody
plants. The principle culprits in our area are bush honeysuckle, common buckthorn, and prickly ash. The first two are exotics,
introduced in this country from other parts of the world.
Although prickly ash is a native, it is still a problem because
it is so unpleasant to have in the woods. All three are fire-sensitive,
and they are classic invaders of areas that have been protected
Another group of invasive plants that are a problem primarily
in savannas are the various Rubus sp. (brambles;
black and red raspberry, blackberry, dewberry). Although native,
they are so invasive that their control is essential. Without
control, large areas of restored savannas will become virtually
Finally, sumac (both smooth and staghorn) are native species that are highly invasive and must be kept under control.
Honeysuckle has been especially bad at Pleasant Valley Conservancy
in areas that had been disturbed, either by previous logging
or by tree fall. Buckthorn was especially bad in the bur oak
savannas. Prickly ash was specially bad in savanna areas that
had once been grazed. In shady woods, brambles are only a
minor component, but once increased sunlight becomes available
due to savanna restoration, they flourish. All of these species
are being removed as part of our savanna restoration work.
When we first started restoration, we focused on these three
shrubs in the understory of the savanna. Because we had not
yet begun serious cutting of larger trees, we hired an herbicide
applicator to carry out basal bark treatment using trichlopyr
(Garlon 4) mixed in diesel fuel. Garlon 4 is oil soluble and
passes readily through the bark. It is translocated to the
roots, where it acts.
The basal bark procedure used was to mark 100 foot wide swaths
from the bottom of the hill at Pleasant Valley Road to the
top of the ridge. The applicator then moved up the hill, back
and forth, spraying the base of each stem with the Garlon
mixture. The spray was spread in a zone about six inches high
around the base of the stem. A blue dye was used to control
the spraying pattern. Everything in the path that was bad:
honeysuckle, buckthorn, prickly ash, was treated. Due to the
volatility of the treatment, the work was done in the winter.
This approach worked quite well, and surveys the following
year showed that over 90% of the target shrubs were killed.
This procedure has also been used on invasive shrubs in the
There are several species of bush honeysuckles
that cause problems in our area, including Lonicera morrowii, L. maackii, L. tatarica, and the hybrid Lonicera X bella. However, there is no reason to
attempt to distinguish them since they are all nonnative and
they are all bad. The native honeysuckle in our area (Lonicera
reticulata and L. dioica) can easily be distinguished
from the bad ones because the natives are all woody vines
rather than bushes.
Bush honeysuckles are upright shrubs ranging
from a few feet to 15 feet tall. They form many branches from
the base, and the spreading branches shade other plants. In
a honeysuckle "thicket", almost nothing will be
found under the canopy. (After the honeysuckle is removed,
the soil is often bare.) Honeysuckles form fragrant tubular
flowers, followed later by red fruits. Birds are attracted
to the fruits and spread the seeds. Bush honeysuckles have
a wide environmental tolerance, but they prefer partial to
full sunlight and are most commonly found in abandoned fields,
forest edges, roadsides, and other open upland habitats. They
are extremely invasive and can easily take over and dominate
Bush honeysuckle is one of the plants that will invade a
habitat if it is protected from fire. Once honeysuckles have
conquered a habitat, there is no possibility of fire because
there is no fuel. In order to reintroduce fire, it is essential
first to eliminate the honeysuckles and then reseed with native
plants, preferably seed mixtures containing grasses that will
carry a fire.
Both mechanical and chemical methods are used on honeysuckle,
and often both together. The most assured method is to cut
all the stems of a plant and treat each cut stump with a 20%
solution of glyphosate. The concentration given here is percent
of the active ingredient.
can be cut with either a brush cutter or a hand lopper. For
an occasional plant, a hand lopper is fine, but for any extensive
honeysuckle thicket, a brush cutter is essential. With a brush
cutter, a sharp saw blade is preferable. For very large bushes,
a chain saw must be used.
With a group of volunteers, an ideal way to work is with
one person operating the brush cutter and several persons
following with herbicide. (A skilled brushcutter can cut enough
to keep three or four volunteers busy treating!)
However, a single person can also make significant inroads
into a honeysuckle thicket. Here is a procedure guaranteed
to work: Cut each stem with a hand lopper or handsaw, counting
the stems as you cut. Cut the stems as close to the ground
as possible, but still leave a small amount of stem showing
above the soil layer. Pull all cut stems away from the base.
Now treat each cut stump carefully with the glyphosate mixture.
It is strongly recommended that a red or blue dye be added
to the herbicide mixture, so that treated stumps can be distinguished
from untreated ones. (Dyes suitable for herbicide use can
be obtained from an agricultural chemical supply house.) As
you treat, count each stump again, and do not stop treating
until you have treated every stump you have cut. If a spray
bottle is used, do not spray the whole base, since this wastes
herbicide and spreads it around. Instead, place the tip of
the spray bottle onto each cut stump, press gently to bring
up several drops of solution, and spread them around the cut
stump with the tip of the bottle. The whole cut stump should
be colored with the dye/herbicide mixture. With practice,
this procedure works quite well and the honeysuckle plants
should not resprout.
Honeysuckle can be cut and treated at any time of the year,
although the winter is often preferable because of the lack
of foliage. Glyphosate does work in winter! (Here
is a research paper on this topic. Ecological Restoration
Vol 22, June 2004, pp. 145-146.)
Small honeysuckle plants can also be killed by spraying the
leaves with a 1-2% solution of glyphosate (active ingredient).
It is important that all leaves be sprayed. Honeysuckle is
so sensitive to glyphosate that the plant should be killed
within a few weeks. More importantly, the root system is also
killed, and within a year the dead shrub can be readily pulled
Honeysuckle is very persistent, and will resprout readily
if not treated with herbicide. Please note: There is no point
in cutting honeysuckles if the cut stumps are not going to
be treated with herbicide.
We do not recommend hand pulling, as some authorities do,
because it disturbs the soil and opens it up for establishment
After the honeysuckles have been taken care of, the area
should be reseeded with native species. This is especially
important because when the honeysuckles were removed a "hole"
has been created, into which weeds will readily move. In fact,
if the honeysuckles were almost solid, it might be preferable
not to remove them all at once, but to gradually cut them
back, seeding with native species as you go. It may take several
years to eliminate the honeysuckles in this way, but this
may be preferable to creating a habitat full of weeds!
Once large honeysuckles have been eliminated from a natural
habitat, the work is not finished. There will be a seed bank,
so that small honeysuckles will appear next year. Fire will
top-kill these new plants but will not eliminate them.
It is essential to return to the area periodically to remove
buckthorn (Rhamnus cathartica)
Download PDF (13 MB) of Power Point presentation given at IPAW meeting Dec. 2011
Buckthorn (Rhamnus cathartica) is one of the
more annoying invasive plants to deal with. Introduced
in the 19th century, it has become well established
over eastern North America. Even though its evils are
now well recognized, it is still sometimes used commercially
as a hedge or ornamental.
infestation in a natural area in late fall. This
species retains its green color long after all native
species have senesced and turned brown. At this
time of year it is very easy to detect.Note: This photo was NOT taken at Pleasant Valley Conservancy!
In many natural areas buckthorn is the predominant understory
shrub in woodlands and savannas, and it is also common
on roadsides. The buckthorn plant may grow as a many-stemmed
bush up to 10-15 feet high, and when older can often
take the form of a small tree up to 30 feet high. Many
specimens in well established stands can be over 50
years old. It produces a chemical that is toxic to other
plants, which may explain the monospecific stands it
often forms. Although the species is dioecious, the
ratio of female to male plants can be as high as 6:1,
making it a prolific berry producer. A very high seed
bank (620 seeds/ m2 ) was reported in Canadian work.
Buckthorn plants produce a chemical (toxin) which is
active in soil. A major buckthorn infestation may result
in a "buckthorn desert". After eradicating
the buckthorn plants, it may take a few years for the
toxin to dissipate.
According to work in England, where it is native, common
buckthorn is a strong calciphile, and is found chiefly
on alkaline peat and limestone soils. This may explain
its absence from many sandier areas.
If an oak savanna area has a lot of buckthorn, special
attention should be placed on its eradication. Although
the original (“old-growth”) buckthorns are readily eliminated
by cut stem or basal-bark herbicide treatment, the huge
seed bank makes total eradication much more difficult.
The first growing season after the buckthorns have been
removed there may be a large number of small seedlings
derived from the heavy seed bank. If allowed to persist,
within a few years there will be small patches and major
infestations visible. The buckthorn have a very extensive
root system with rhizomes growing horizontally sometimes
5-10 feet to areas where new shoots develop. The root
system of buckthorn is a massive fibrous tangle of small
and large roots.
seedlings coming up in an area where a large infestation
had been cleared the previous winter. The seed bank
is quite prolific.
Pulling buckthorn plants does not eradicate
an infestation It is virtually impossible to pull up
all of the tangled underground plant mass of a buckthorn
stand. The following year new shoots arise and reinitiate
Fire does not eradicate buckthorn plants. Buckthorn plants are not eliminated even by annual burning.
All fire does is top-kill the shoots. Numerous dormant
buds then begin to grow and send up stems. In some cases,
as many as a dozen new shoots can arise from a single
root collar. It is possible that in restored prairies,
where much hotter fires occur and tall grasses and forbs
shade the soil, that buckthorns will be outcompeted,
especially if the prairie is burned every year. However,
in savannas and open-oak woodlands, where buckthorn
infestations are most common, hot fires are less common
and most of the understory plants are not tall grasses.
Girdling does not eliminate buckthorns. Although
several weed manuals prescribe girdling as a method
to eliminate buckthorn, this is completely ineffective.
The following year there will be numerous shoots arising
from the area below the girdle. Buckthorn plants have
numerous dormant buds just waiting for the elimination
of apical dominance.
Herbicide treatment is essential for
eradication of buckthorns, but not all herbicides are
equally effective. Many reports have prescribed the
use of glyphosate for treatment of cut stems of buckthorn.
Although glyphosate is effective for winter treatment
of cut stems of large buckthorn shrubs, it is ineffective
for treatment of the small cut stems that develop from
the seed bank. Probably because of the massive root
mass, getting the herbicide to the critical parts is
impossible if herbicide is only dabbed on the tiny cut
stem. The only herbicide recommended for cut stems is
triclopyr, sold under tradenames such as Garlon or Element. The oil-soluble version (Garlon 4 or Element 4) and it should be used at 15-20% concentration. This permits use as a basal bark treatment. Both the cut stem and the stem below the cut should be treated.
For small buckthorn stems, basal bark with the paint stick method works very well. Use Garlon or Element 4 at 15-20% in oil. The fall of the year is an excellent time to work, since buckthorn retains its green leaves after the native vegetation has turned brown, making it easy to detect.
resprouting around a buckthorn cut stem that had
not been treated with herbicide.
Triclopyr (Garlon 3A or Garlon 4) is the most effective
herbicide for buckthorn, both small and large. For the
large buckthorn shrubs, it is very effective as a basal
bark or cut stem treatment (Garlon 4 at 15% active ingredient
in oil). For the large patches of small plants from
the seed bank, it is effective as a foliar spray (active
ingredient of 3-4% Garlon 3A in water). It is essential
that follow-up in future years be done, and any missed
However, although not recommended for cut stem treatment, glyphosate is effective as a foliar spray (4-5% of the concentrated product) for small plants.
The key to eradication of buckthorn is a combination
• Remove large buckthorn plants by cutting and basal-bark
herbicide (Garlon 4) treatment, or by basal-bark treatment
alone. Large plants that have been basal-bark-treated
without cutting die in the first growing season and
fall over in a few years. Cutting without herbicide
treatment is worthless and pulling or digging will not
remove all of the root mass from the soil.
• Buckthorn eradication is a multi-year task. Follow-up
treatments of all areas of infestation must be made.
• After the initial removal, monitor the site carefully for the new seedlings that
will inevitably arise from the seed bank, and immediately
foliar spray with triclopyr (4-5% Garlon 3A). Plants should
be sprayed in the spring, as soon as they are visible
(around mid-May in our area).
• Carry out controlled burns only after all plants have
been cut and treated or foliar sprayed. Burning before
herbicide treatment should not be done because all it
will do is top-kill, and there will be no living stems
left to transport herbicide to the roots. Also, burning
will only result in resprouting and the formation of
many stems where one was originally.
• Do foliar spraying with triclopyr in the fall after
the native vegetation has senesced. Buckthorn retains
its foliage in the fall for weeks after the native vegetation
has died back. This makes it possible to use a foliar
• Hand-cut and herbicide-treat small buckthorns in the
winter. Although laborious, this procedure should be
the most benign as far as the native vegetation is concerned.
The herbicide should be triclopyr (15% active ingredient
in oil) used as a basal bark. Do not treat only the
cut stems, but also spray the stem below the cut down
to the root collar (basal bark treatment), using a hand
spray bottle. Avoid getting any herbicide on the soil
itself, as triclopyr has a soil residual and may prevent
native forbs from becoming established (although triclopyr does not affect grasses)..
• Burn in the spring in areas where buckthorn plants
have already been removed. Spring burning is the best
because it will come after the fall/winter control work,
so that there should be no remaining buckthorn stems
to be top-killed. Burning will also encourage the growth
of native species, and their competition will hopefully
help to suppress new buckthorn growth.
• Reseed with native species, especially in areas where
large buckthorn infestations have been eradicated. For
areas where triclopyr has been used, reseed predominantly
with native grasses, since they are not affected by
the herbicide. Although these areas may well start out
as “buckthorn deserts” due to the residual effect of
the buckthorn toxin, they should be planted anyway,
since some of the newly planted species will become
established. Unfortunately, there is no research on
whether any native species are resistant to the toxin.
Experience has shown that native species begin to dominate
about the third year after buckthorn removal.
• Continue monitoring for new infestations, and deal
with them by the above methods.
How long will the seed bank last? Unfortunately, there
are no data on this, although in England (where it is
native) casual observations suggested at least two or
Download PDF (13 MB) of Power Point presentation given at IPAW meeting Dec. 2011
Buckthorn at Pleasant Valley Conservancy
Common buckthorn (Rhamnus cathartica)
has been a serious invader of the oak savanna areas at Pleasant
Buckthorn was introduced into
North America as an ornamental. It was planted for hedge rows
in Wisconsin as early as 1849. Despite its insidious nature,
it is still legally sold as an ornamental. It has become naturalized
and has spread over most of the southern and eastern parts
of the Wisconsin. Buckthorn is an especially troublesome invader
of natural oak savanna and oak woodland areas of southwestern
The large buckthorn plants were dealt with by basal bark treatment with Garlon 4. Swaths were marked up the south slope and across the ridge top, and every buckthorn (as well as honeysuckle and prickly ash) was treated. This procedure was done in the winter, at snow-free times. The treated shrubs did not leaf out in the spring. Within two or three years, their roots rotted away and they fell over. The basal bark method is the most economical because it does not require cutting or burning. Once dead, the plant can be cut
and removed, or allowed to stand to rot.
We have used this procedure extensively at Pleasant Valley.
It has the advantage that it is quick and does not require
any cutting. However, if we are removing trees at the same
time, the cut stump procedure described above is preferable.
After an area was cleared, it was burned and then seeded with native savanna species. Burning provided extensive bare areas, providing open areas for the seeds to become established.
The buckthorn seed bank. Because of the extensive seed bank, it was necessary to return to cleared areas and attack the new buckthorn plants that arose from the seed bank. Ideally, all new seedling should have been sprayed with triclopyr or glyphosate (at foliar concentrations), but this was not done. Thus, we had to return later, when the seedlings had already developed into small plants. Although the seed bank is no longer a problem, these small to medium sized buckthorn plants continue to be a problem. Every year we work extensively on several of our savanna areas, especially in the ridge top savannas where buckthorn presents the greatest problem.
Download PDF (13 MB) of Power Point presentation given at IPAW meeting Dec. 2011
The term "bramble" refers to a whole group of plants
of the genus Rubus, which include blackberry, red
and black raspberry, and dewberry. Brambles are a minor component
of the degraded savanna, but once the habitat is opened up
and light reaches the forest floor, brambles can grow rampantly.
Although our brambles are native, we still consider them undesirable
because they tend to take over the savanna. (Brambles are
less of a problem in prairie restoration.)
Brambles are biennial plants but have a perennial root system.
The roots continue to grow for the life of the plant, but
new above-ground shoots (generally called "canes")
develop each year. The first-year shoots grow vegetatively
but do not flower. In the second year these shoots flower,
set seed (berries), and then senesce and die.
The photo below shows the arrangement of canes, shoots, and
roots at the base of the plant. There are several dormant
shoots. Iif the above-ground shoots are killed by fire or
cutting, one or more of the dormant buds will begin to grow
and form a new canes.
Some brambles (black raspberry, northern dewberry) exhibit
a phenomenon called "tip-rooting." Canes whose tips
reach the soil can form new roots, enabling the brambles to
colonize new bare areas. Bramble patches with tip-rooted canes
are especially difficult to walk through.
Since flowers only develop on the second year shoots, annual
fire will keep brambles from flowering and setting seed, but
will not eradicate them. In the next growing season, each
killed cane will develop a rosette of leaves from an underground
bud. By mid-summer, a new vigorously growing cane has been
Control of brambles in savanna restoration Although they are very fire-sensitive, they are not eradicated
by burns, since the roots remain alive and resprout. Eradication
of brambles in savanna restoration can only be done with the
use of herbicide. Even then, removal requires careful monitoring
and consistent control.
Bramble canes can be cut and the cut stems treated with glyphosate
(20% active ingredient), as described above for honeysuckle.
This procedure works well for blackberries, and reasonably
well for black raspberries, but is generally ineffective for
red raspberries. This latter species is a prolific clone former,
and has an extensive underground root system. Herbicide treatment
of cut stems does not work.
Brambles are easily cut with hand clippers, and a single
person can cut and treat an area, with clippers in one hand
and herbicide bottle in the other. It is essential that every
cane be cut and treated. Some of the canes may be dead. These
do not need to be treated, although it is still desirable
to cut them. Living cut stems are easily recognized because
they will be green and moist, even in the winter. Eradication
by the cut-and-treat method is very time-consuming, but is
the surest way. Once the brambles have been removed, annual
burns should be carried out for a number of years, since there
will always be a seed bank, and in the absence of fire the
area would eventually return to an unrestored state.
In areas with large bramble patches, especially those where
there are no "good" plants, foliar spraying can
be done. Roundup (glyphosate; 1-1.5% foliar spray) is labeled
for blackberry and should work on other members of the genus Rubus. According to the manufacture, best results
are obtained when plants have reached full leaf maturity in
late summer or fall. Garlon (triclopyr; 0.5-1% foliar spray)
and Krenite (fosamine; 5-10% foliar spray) are also labeled
by their manufacturers for blackberry and would presumably
work for the others. However, all of these herbicides have
the potential for harming nontarget plants and should only
be used in areas where there are no desirable plants.
One additional procedure that may aid in bramble control
is to cut the plants in mid-summer, at flowering time. At
this time of year, most of the nutrients are in the stems,
and if these are severed the roots will be starved. We have
found this procedure to be helpful, although it does not completely
eliminate the brambles. One advantage of cutting at flowering
time is that berries will not yet have been made, thus eliminating
the chance of adding to the seed bank.
Brambles are very sensitive to fire and are readily top-killed
by a good burn, but the dormant buds (see photo above) soon
begin to grow and form a rosette of new leaves. These rosettes
can be treated with herbicide, such as glyphosate or triclopyr,
at the low concentrations suitable for foliar spraying.
Rubus always has an extensive seed bank, so that
effective bramble control requires frequent, preferably annual,
burning as well as reseeding with herbaceous savanna species,
since competition from other plants is an important factor
in keeping brambles from becoming reestablished. Because fire
will not eliminate the seed bank, it is also essential to
return to previously restored areas periodically and repeat
the cut-and-treat method.
Getting rid of sumac at Pleasant Valley Conservancy
See this link for a separate web page on the biology and eradication of sumac. The present page describes work at Pleasant Valley Conservancy
Smooth sumac is a native shrub that can be a
real menace in prairie and savanna restoration. It is fiercely
clonal and spreads wildly from rhizomes. Left alone, it can
take over a site and shade out everything else. Although annual
fire keeps it under control, all one needs is a year or two
without fire and it can be so big that fire won't get at it.
In the fall of 2008 we did a major survey for
sumac, and located at least 100 clones using GPS. These clones
are shown on the map here. Each red dot represents a single
clone, often with 50 or more stems. Click
here to see how we are eradicating them.
sumac. We started our sumac work in November 2008, using the database depicted in the above map. When the early December snows came, we were stalled and did not return to finish the work until early March 2009. We used backpack sprayers and basal barked all sumac stems in a clone, using Garlon 4 in oil.
At the same time that we were basal barking sumac, we also basal barked brambles, buckthorn, honeysuckle, gray dogwood, prickly ash, or any other undersirable woody vegetation.
All of the sumac clones were also burned during our spring burns, as described in this link
The basal bark treatment was quite effective and an underground examination of the stems showed that there were no living buds. Note that the buds were dead not because of the burns, but because of the basal bark herbicide treatment.
Although the basal bark work killed the stems as well as the bud that was at the base of each stem, buds in the rhizomes themselves were not killed. The herbicide obviously is not transported along the rhizomes, or perhaps it is impossible to apply a high enough concentration to kill these buds.
Thus, we had living shoots developing among the clones that had been basal barked. I did a count on one large clone. There were about 120 dead stems. By mid July there were almost an equal number of new shoots.
Kathie set up an experiment on a large clone that had been basal barked but on which there were about 250 new shoots. She cut all of these with a hand lopper (a brush cutter could also have been used), and then did a basal bark treatment with Garlon 4 of all of the cut stems. This clone was carefully marked and observed for the rest of the summer. The basal bark treatment was very effective, and no new shoots were seen. However, we will have to wait until next year (or the year after) to see if we have completely eradicated this clone.
We tried a different approach on some other clones that had many new stems. Instead of cutting the new stems and treating the cuts, we simply basal barked the new stems, using a spray bottle. All treated stems died. Again, we will wait to see what happens next year.
Another sumac control activity will probably be more certain. We located all of the single (non clonal) sumac plants growing in either our prairie remnants (south-facing slope) or savanna remnants. Starting in early August, our summer interns basal barked these single plants. Within two weeks, all treated plants were dead. Since these are single plants rather than clones, there are no rhizomes to provide new buds, so we are assuming these plants will be killed. A number of these plants have been marked and will be monitored in 2010. Note that the single plants I basal barked in 2008 died and no new growth has occurred.
Our work at Pleasant Valley Conservancy has shown that basal bark treatment with Garlon 4 is highly effective, and as long as one works to eliminate all new shoots arising from rhizomes one should be able to eradicate sumac. This is certainly a much more effective way that simply mowing, which does not eradicate. However, it is a multi-year job.
|See this link for a new (2012) summary at Tom's Blog