Control of invasive
species, both woody and herbaceous, generally becomes a major
part of any oak savanna restoration project. The principles
and techniques presented here are applicable to both the initial
restoration work and the long-term management of the savanna.
In many situations, the original restoration work moves quickly
into long-term management.
Although there are some differences across the Midwest states
in the invasive shrubs that cause the most problems, the principles
of control for all these species are similar. Often site to
site variation within a state may be greater than state to
Shrubs differ from trees. They are shorter (usually under
15 feet tall), have multiple stems, and have shorter life
spans. Some trees grow occasionally as shrubs, generally when
young. Also, a few species of shrubs can develop into trees,
especially under protected conditions.
Shrubs are widely used in residential and commercial landscaping,
and there has been a tendency to use certain nonnative species
because they are more successful under the generally harsh
conditions that often prevail. Unfortunately, some of these
nonnative species have “escaped” into natural areas, where
they present considerable problems.
Out of ignorance, some nonnative shrubs have even been highly
recommended by government agencies to landowners and commercial
growers. Buckthorn, honeysuckle, multiflora rose, and autumn
olive have in the past been widely planted. Buckthorn is still
used commercially, although efforts are now underway in some
states to make its use illegal. The tendency now is to substitute
suitable native shrubs.
shrubs of the Midwest
species that may be invasive
raspberries, and dewberries
A characteristic growth pattern of all shrubs is the ability
to resprout if the main trunk is cut. Shrubs (like plants
in general) exhibit a phenomenon called apical dominance,
arising because the main growing bud of the shrub produces
a growth hormone that is transported to the roots and inhibits
the growth of dormant buds. When the hormone source is eliminated
by cutting, growth of a few or many of these dormant buds
is initiated, resulting in the production of multiple shoots.
Eventually, over a few more years growth, one or two of these
new shoots may become dominant and produce enough hormone
so that buds at the base go dormant again.
Pruning a shrub to control its shape and form makes use of
the apical dominance phenomenon. Top-killing a stem by fire
also eliminates apical dominance.
Whether apical dominance is eliminated either by cutting,
girdling, or fire, the end result is the same: multiple shoots
develop. It is not possible to eradicate a shrub simply by
cutting it, and fire also does not eradicate.
Clonal growth of shrubs
Certain species of shrubs spread by means of horizontal stems
called rhizomes which grow underground for some distance from
the original plant before forming new above-ground shoots.
Species in the above table that are clonal are buckthorn,
gray dogwood, red-osier dogwood, sumac, Rubus species,
and prickly ash. To eradicate these species the whole clone
must be eliminated.
growth of prickly ash (Xanthoxylum
americanum). Although this is a native species and
good bird habitat, only a few clones should be retained
in any savanna restoration.
The goal of herbicide treatment is the complete killing of
the shrub, and many
herbicides are effective for this action. Herbicide applied
to the cut stems of a shrub is transported to the roots where
it accumulates in the roots, root collar, or basal stem. The
herbicide either kills or inhibits the growth of the shrub.
However, if insufficient concentration of herbicide is applied,
the living shrub tissue may “escape” treatment and begin to
grow again in a following season. This is one reason why a
single herbicide treatment may not be sufficient to eradicate
to the contrary, cut stems of shrubs can be treated with herbicide
in the winter.
Control strategies for shrubs
Techniques for eradication of invasive shrubs make use of
the principles of shrub growth just discussed. In most cases
herbicide will be needed as part of an integrated management
• Cut and treat. All the stems are cut (by
chain saw, motorized brush cutter, or hand loppers), and every
cut stem is treated with a suitable herbicide.
• Basal bark. The bases of the stems are
sprayed with an oil-soluble herbicide dissolved in a penetrating
diluent such as diesel oil, kerosene, or bark oil. The oil
penetrates the bark and carries the herbicide to the stem
where it is transported to the roots.
• Foliar spray. The shrub is sprayed with
an aqueous solution of an herbicide. The herbicide is taken
in through the leaves and transported throughout the plant,
resulting in death of the plant.
• Girdle herbicide application. If girdling
is to be used, an herbicide is applied to the cuts. Either
a water soluble or an oil soluble herbicide can be used. Girdling
alone will not eradicate shrubs. All it does is eliminate
apical dominance, resulting in growth of dormant buds. Where
a single stem might have been present before girdling, several
to many new shoots will arise.
• Hand pulling most likely will not eradicate shrubs. Hand
pulling is often recommended by those trying to avoid the
use of herbicides. Certain species can be eradicated by this
method, but many shrubs have impressive root systems, parts
of which are left below ground when the shrub is pulled and
grow and restablish the infestation.
Basal bark treatment
For the initial stages of an oak savanna restoration, or for
a major infestation, the most economical method is the use
of basal bark treatment. This should be effective for all
of the shrubs listed in the table above, although some may
be more difficult to treat than others due to their physical
Basal bark treatment is recommended for woody plants less
than six inches in diameter, which would include almost all
An herbicide which has been widely used for basal bark application
is triclopyr, in the form of its butoxy ethyl
ester (trade name Garlon 4; 61.6%, 48% triclopyr
acid equivalent ). Garlon 4 should be used at a 20-30%
solution (20 ounces or 30 ounces of herbicide in 100 ounces
total product). It can be mixed with mineral oil, “bark oil”,
or “Diluent blue” (available commercially from agricultural
chemicals supply companies). The commercial diluent contains
a dye which aids in proper application. If a diluent such
as mineral oil is used, a red or blue dye obtained from an
agricultural supply company can be used.
The basal bark procedure involves spraying a 10-15 inch band
of herbicide at the base of each stem. Spray to thoroughly
wet the whole area, but not to the point of runoff. A nozzle
with a flat fan spray pattern is ideal and a low-pressure
sprayer is recommended. To prevent spray moving past the target,
keep the nozzle close to the stem being sprayed. Application
can be done at any time of the year, including winter, except
when the stems are wet or have snow on them. This procedure
works because the bark is lipophilic, and the oil diluent
readily wets the bark and allows oil-soluble substances such
as the herbicide to penetrate.
Although it is recommended to spray completely around the
stem, for small stems (less than one inch in diameter), one-sided
spraying can be done, applying a 10-15 inch band of herbicide.
Basal bark treatment has a number of advantages:
• Effective year around (although not recommended when the
air temperature is above 70 F).
• Highly selective, since only the plant sprayed receives
• Herbicide can be applied from a backpack sprayer, making
it possible to move quickly through the area.
• Herbicide is confined just to the plant, reducing any effect
on surrounding native species.
• If used during the dormant season, the treated shrub does
not leaf out the following spring. Thus, there are no brown
leaves. This has an advantage in public areas.
• No cutting is needed. The roots of the dead shrubs will
eventually rot and the shrub will fall over. Since the leaves
are eliminated right away, increased light to the forest floor
occurs, encouraging growth of native species. Overseeding
of native species should be done in areas where large infestations
have been treated.
sprayers are best for basal bark application of herbicide.
Snow-free periods during the winter are excellent
times for this work. Here a sumac clone is being treated. This clone had been marked in the fall from its characteristic red leaves, so that it could be attacked when time permitted.
Cut stem treatment
A general method suitable for all shrubs is to cut them with
a saw, loppers, or hand clippers and spray the cut stems with herbicide. This works very
well for small-diameter shrubs or large clones where basal bark treatment
is difficult. For large infestations, a powered brush cutter or chain saw should be used.
Either Garlon 3A in water or Garlon 4 in oil can be used to treat the cut stems. The latter has the advantage that occasional stems that missed the cutter can be basal barked.
For small shrubs or minor infestations, the cut stems can
simply be left on the ground where they will burn up during
the next prescribed burn. If a large shrub infestation is
being dealt with, the cut stems should be piled so that they
can be burned later. Once the stems have dried for a few months,
they will be flammable and can be ignited easily. See
link for brush piles procedures.
Note that cutting without herbicide treatment should not be
done. It is ineffective, and there will be extensive resprouts
from the cut stem the next growing season.
Several herbicides are suitable for cut stem treatment although
not all of them are equally effective. The table below has
stem work can be done either with hand-held loppers or
a motorized brush cutter. A dye should be added to the
herbicide mixture to ensure that treatment is complete.
recommendations for cut stem treatment
(Garlon 3A or 4)
(Garlon 3A or 4)
(Garlon 3A or 4)
4 as basal bark, either with or without previous cutting
4 as basal bark, either with or without previous cutting
raspberries, and dewberries
(Garlon 3A or 4)
(Garlon 3A or 4)
should be used at 20-30% active ingredient (the label will indicate
the concentration of active ingredient in the product itself). See also this link
has the advantage that it has no residual activity in the
soil, as it is inactivated by soil particles. However, glyphosate
is less effective against buckthorn, multiflora rose, or sumac.
Sumac has an additional problem. It has a milky sap which
prevents water-soluble herbicides from moving down the cut
stem. The best procedure with sumac is to use Garlon 4 in
oil as a basal bark, either with or without cut stem treatment.
For smaller infestations foliar spraying with glyphosate or
triclopyr can be done. If the shrubs are scattered and surrounded
by good species, then selective spraying of the leaves with
a backpack sprayer should be done. In an area where there are
no “good” species, broadcast spraying with high-volume equipment
can be very economical. The herbicide concentration used for
foliar spraying is much lower than that used for basal bark
or cut stem treatment. The herbicide label will specify the
concentration to use. In general, the concentration is between
2 and 4% "out of the bottle"..
If foliar spraying is desirable but the infestation consists
of large-sized plants which cannot be sprayed without contaminating
the environment, an alternate approach is possible. Cut the
shrubs with a brush cutter or chain saw and remove the cut material
from the site but do not treat the cut stems. Allow the resprouts
to grow until they are about six inches tall and then use a
foliar spray. The initial cut should best be done in mid summer,
so that the resprouts can be sprayed at the end of the summer
while they are still growing.
Management of a shrub removal activity
The overall management of shrub removal, especially in the initial
stages of oak savanna restoration, should be organized systematically.
If basal bark treatment is being used, the area to be covered
should be divided into swaths of 15-20 feet wide, marked with
flagging, using a compass to keep a straight line. The worker
or workers then walk back and forth along this swath and basal bark every undesirable
shrub. Once the swath is completed, return via the
next swath. Move back and forth until the whole unit has been
If tree removal is also being done, then the two activities
can be done at the same time. If the trees being removed are
being burned at the site, then the cut shrubs should be burned
at the same time the tree slash is burned. Since the cut shrubs are small, they can be easily ignited and can serve as the base for the burn pile.
buckthorn (Rhamnus cathartica)
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.
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. 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. This chemical activity may explain why dense monospecific stands of buckthorn
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 plant forms a very extensive
root system, and dormant root masses may persist for years in a formerly infested site. 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
can be 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.Glyphosate is effective in killing seedlings or small resprouts (foliar spray at 2-4% concentration). It is also effective for cut-stem treatment
of large buckthorn shrubs, but glyphosate is less effective in treating small cut stems. Garlon 4 in oil should be used; treating not only the cut surface but dribbling herbicide down the side of the stem (basal bark treatment). 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
The leaf spritz method A very effective method for control of leafy buckthorn stems from mid summer until early fall is the leaf spritz method. This involves using a hand spray bottle containing 20% Garlon 4 diluted in bark oil. Two or three of the upper leaves on each buckthorn stem are given brief "spritzes", so that the herbicide spreads out on the leaves. Within a few days the stem will be visibly damaged and within a week will be dead. This technique is very benign to surrounding native plants, as the herbicide is confined to the upper area of the buckthorn plant. Since small buckthorn plants generally consist of multi-stemmed colonies, it is essential that "all" stems are treated.
||Buckthorn stem that had been spritzed with Garlon 4 in oil a few days before. When done in mid-summer, when buckthorn is growing rapidly, this treatment usually results in death of the stem within a week. It is essential that all stems of multi-stemmed buckthorn plants be treated.
resprouting around a buckthorn cut stem that had
not been treated with herbicide.
Note that it is essential
to follow-up the buckthorn control in future years be done, since there will almost certainly be resprouting from dormant root masses.
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.
• Monitor the site carefully for the new seedlings that
will inevitably arise from the seed bank, and immediately
foliar spray with triclopyr (5% Garlon 3A). Plants should
be sprayed in the spring, as soon as they are visible
(around mid-May in our area). Glyphosate is also effective as a foliar spray at 2-3% concentration, but is not advised for use on cut stems.
• 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.
There are at least three periods of the year when buckthorn control is recommended..
Of course, basal bark can be done any time of the year, even winter, although it takes more skill in the winter to find the naked buckthorn stems.
- Late May after spring burns, when backpack sprayers can be used to treat small buckthorn resprouts with foliar Garlon 3A.
- Mid to late summer. This is the time of year when buckthorn leaves are at their maximum height and the leaf spritz technique works great. Spritzing just two or three of the upper leaves from a hand spray bottle is all that it takes to kill a stem. (See this link for more detail.)
- Mid-October to mid-November when using basal bark treatment with Garlon 4.
• 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
spray selectively. However, the timing of foliar spraying is tricky, since as soon as the stems start losing leaves, foliar spray starts to become less effective.
• 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 (15-20% 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 will prevent
native forbs from becoming established.
• 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. Burns will also top-kill and buckthorn plants that have been missed. The new shoots from these top-killed plants will be visible within a month and can be sprayed with foliar triclopyr (Garlon 3A) (glyphosate also works as a foliar spray at this time of year).
• 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 small buckthorn plants have been found in restored oak savanna areas in Wisconsin as long as 10 years after initial eradication. These have probably arisen from dormant root masses.
several species of bush honeysuckle 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 a habitat.
bushes invading a natural area. Photo taken in early
spring when the plants are just leafing out.
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 (active ingredient) of glyphosate.
Honeysuckle can be cut with a chain saw, brush cutter,
or hand lopper. For an occasional plant, a hand lopper
is fine, but for any extensive honeysuckle thicket,
a motorized cutter is essential.
honeysuckle is a multiple-stem bush. After cutting,
it is essential that all cut stems be treated. Adding
a red dye to the herbicide is a good way to ensure
complete treating. When using a hand loppers, count
each stem as it is cut and count again as they are
With a group of volunteers, an ideal way to work is
with one person operating a brush cutter or chain saw
and several persons making brush piles and treating
the cut stems with herbicide. (A skilled brushcutter
can cut enough to keep three or four volunteers busy
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.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 (see photo). 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!
Small honeysuckle plants can also be killed by foliar
spraying with a 2-4% 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 up.
Honeysuckle is very persistent, and will resprout readily
if not treated with herbicide.
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.
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. After a few years, there will be
numerous knee-high plants scattered throughout the savanna.
Although these can also be cut and treated, a more efficient
way of dealing with the honeysuckle resprouts is by
foliar spray in the fall of the year, after the native
vegetation has senesced. The honeysuckle leaves remain
green and viable and can be easily seen sprayed at that
time. Glyphosate works well, and because the native
vegetation has all senesced it will not be affected.
Add a blue dye to the herbicide in order to be able
to follow the foliar spray.
spray with glyphosate works very well with honeysuckle
in the fall of the year, after all the native vegetation
has senesced. Timing is a little tricky, and years
will differ. It is also advisable to use a higher
concentration of glyphosate (8-10% active ingredient).
The blue dye permits monitoring the efficiency of
"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.
of black raspberry (Rubus
occidentals) in a restored bur oak savanna.
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.
underground system of a black raspberry plant.
Bramble resprouts developing from a clone that had
been top-killed by fire. Control is possible by
foliar spraying with triclopyr early in the spring,
when the rosettes are still small.
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 established.
patch burning during a savanna burn. The principle
fuel is oak leaves, but the leaves of the brambles
themselves also burn. Brambles are very sensitive
to fire and top-killing is usually virtually complete.
The resprouts that arise the following spring (see
photo above) should be sprayed with triclopyr.
Control of brambles in savanna restoration
Although they are all 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.
The surest way of removing brambles is by cutting the
canes and treating the cut stems with glyphosate (20%
active ingredient). 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
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. (Some reports state that Krenite
only affects woody plants, but this is not true. Krenite
also affects many grasses and forbs.)
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.
If fire cannot be used, and desirable nontarget species
must be protected, complete elimination of brambles
from an area is still possible using the cut-stem procedure
described. Although laborious, this procedure is quite
effective. It is best done in the winter, because herbaceous
vegetation will be dormant, thus eliminating any side
damage from the use of herbicide.
In most cases, brambles will be a minor component of
the woody vegetation, with honeysuckle, buckthorn, and
other woody plants dominating. Since all of these species
can be eliminated by herbicide treatment of cut stems,
brambles can be removed along with the others.
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.
The table below summarizes the characteristics of the principle species of brambles likely to be found in oak savanna restoration.
Large canes; do not tip root
Cut and treat with glyphosate or triclopyr
Vine-like; trailing along the ground; tip root
Foliar spray with triclopyr of new growths after burns
Dense clones; do not tip root
Foliar spray with triclopyr of new growths after burns
Long arching canes that tip root
Cut and treat with glyphosate sometimes; triclopyr recommended; foliar spray with triclopyr of new growths after burns
weed control in savanna restoration
is a list of invasive forbs or grasses that are often
experienced in savannas. No savanna would ever be expected
to have all these weeds, but three or four might be
expected. Weeds that are found predominantly in wet
and wet-mesic areas are not included.
herbaceous weeds of possible concern in savanna restoration
and fall spray; hand pull
and fall spray
spray; summer mow; fall spray
pull or dig
and fall spray
pull or mow
pull or mow
pull or mow
and fall spray
pull or mow
pull or mow
pull or mow
pull or mow
and fall spray;summer cut followed by spray of
or winter annual
pull or mow
dig or pull; late fall spray with triclopyr or
Severity refers to savannas only. Many of those
listed with low severity are extremely bad in
prairie or wetland habitats.
In contrast to shrubs, weeds are less a problem in savanna
restoration, but if one of the above becomes established,
especially those that are perennials, immediate attention
to eradication is strongly advised, and herbicide use
should not be slighted.
Possibilities for control of weeds is related to their
annual growth cycle.
Annuals do not normally need to be
controlled, although heavy infestations might be mowed
to keep the keep them from going to seed.
Biennials are not generally controllable
in their first year of growth, when they are often difficult
to find. However, they can be foliar sprayed with glyphosate
in the late fall/early winter of their first year, when
they remain green long after the native vegetation has
senesced. In their second year, biennials are best eradicated
by hand pull (or digging). However, heavy infestations
which are too costly to hand pull can be mowed at the
time of peak flowering but before seed set has commenced.
Herbicide use is not recommended in natural areas such
as savannas unless there is no "good" native
Perennials must be controlled by herbicide.
It is virtually impossible to eradicate perennials by
digging or pulling, since not all of the root mass will
be removed. Mowing is completely ineffective for the
same reason. Spraying can be done in the early spring,
when these exotics are usually up and thriving but before
the native species have come out of the ground. Spraying
can also be done in the late fall, when these exotics
remain green and the native species have senesced. In
the summer, they may also be mowed at the time of early
bud stage and the resprouts sprayed about a month later.
Despite the recommendations of some weed manuals, perennial
weeds can almost never be eradicated simply by mowing,
unless the mowing is as frequent as that used for lawns.
For tall perennial weeds such as Canadian thistle, or
native invasive forbs like Canada goldenrod or woodland
sunflower, a suitable approach is to mow the infestation
at the early flower bud stage, and then spray with herbicide
the regrowth some weeks later when it is at about the
six-inch height. For thistle and other species of the
Compositae, the herbicide of choice is clopyralid (see
Shovels for weed removal
Weeds can generally be pulled by hand, but sometimes
a shovel is necessary. Nick Faessler of the Prairie
Enthusiasts has devised and sells (through the Prairie
Bluff chapter) a very handy shovel. He calls it a Parsnip
Predator, because he devised it for control of wild
parsnip (Pastinaca sativa). However, it works for sweet
clover, bull thistle, Queen Anne’s lace, and lots of
other invasive plants of natural areas. The narrow profile
of its blade means that adjacent “good” plants are left
The sale of the Predator is a fund raiser for the Prairie
Bluff folks, and it can be purchased on line. Copy this
link and paste it into your browser: http://www.theprairieenthusiasts.org/chapter/pbluff/PARSNIPP.htm
A homemade version can be made a little cheaper, but
you have to have equipment to cut the blade down. If
you only need one, I’d go with the Faessler version.
home-made Parsnip Predator. The narrow end of the
shovel causes less soil disturbance and makes digging
the weed easier. The tip of the shovel should be
Management of a weed removal activity
A systematic approach to weed removal is recommended.
The area should be divided into manageable units and
the worker or group of workers moves along, keeping
a sharp eye out for undesirable plants. Each worker
carries a shovel, although if the weed can be hand pulled,
this is usually quicker and requires less effort. A
recent rainfall often helps to make the weeds easier
to pull. Set up swaths such as described above for shrubs.
Since each weed has its own season, the site must be
traversed several times during the growing season. Local
experience will be important in deciding when and how
often the site should be surveyed.
If the target is a perennial and herbicide is to be
used, a similar systematic approach should be used,
with each worker having a backpack sprayer with appropriate
herbicide. A blue dye helps to ensure that each plant
is sprayed (and that a plant is not sprayed more than
Weeds of special concern
Two biennials on the above list often become problems after burns: white and yellow sweet clover. This is because the seeds of these species are able to remain viable for long periods in the soil, and fire stimulates them to germinate. Thus, the next year after the first good fire, first year plants appear, often in large numbers. The following year, major infestations of second-year plants develop, which must be dealt with immediately. If these two species are not controlled, the second-year plants will set seed, and you will be back to square one. Because the first-year plants remain green into the late fall/early winter, they can be sprayed with glyphosate at that time. Although this will not kill all the plants in the infestation, it will make a major impact.
Garlic mustard and Japanese hedge parsley are two species from the above list thrive in shady woodland areas and will also grow in savannas. These can be controlled by late fall/early winter spraying of first-year plants, spring spraying of second-year plants, and hand pulling all plants missed by the spraying regimes.
Canada thistle is often a problem in savanna areas. Because it is a perennial, and is also clonal, control requires use of herbicide, but mowing can also help. Many weed manuals recommend mowing at the time of early flower bud stage. The idea is that at this time, most of the root resources have moved to the stems as part of the flowering process, so mowing at that time will starve the roots. However, mowing does not eradicate the clone, but merely sets it back. If mowing is not followed up with herbicide, the clone will thrive and be back in full in another year or two. Here is the ideal approach for Canada thistle: mow as early in the spring as the plants are high enough to mow. Monitor the mowed clone and as soon as new growth has taken place and the plants are in the full rosette stage, spray with clopyralid (Transline or Stinger) or another herbicide specifically recommended for Canada thistle. This herbicide does not affect grasses, which should be seeded into the former thistle clone in order to provide competition for any future development. Control of Canada thistle is a multi-year task, as dormant buds in the clone will form new growth in future years.
Bull thistle may be found scattered throughout a newly restored savanna. It is a biennial and can be readily controlled by digging. As with all biennials, it must be controlled before any danger of seed set.
Reed canary grass is primarily a problem in wetland areas, but does form small infestations in upland sites such as savannas. Reed canary grass is easy to detect at flowering stage, which is the ideal time for control. Patches can be sprayed with a grass-specific herbicide such as sethoxydim (Vantage). Another approach is to tie together the flowering stems of the whole patch, cut the stems above the tie, and squirt concentrated glyphosate (50% or full strength Roundup) down the stems. In the late fall of the year, when reed canary grass is still green but all native vegetation has senesced, patches can be foliar-sprayed with 5-7% Roundup. Because reed canary grass is clonal had has numerous dormant buds, a single treatment will not eradicate. Mark patches that have been treated and return in subsequent years.
Giant mullein is primarily a problem during the early stages of savanna restoration when there are many bare areas, such as burn scars or areas that had been shaded before trees or shrubs were removed. It is a pioneer in such bare areas, but as soon as native vegetation fills in, it is unable to compete. However, it should be removed because its large leaves sprawl out over the ground and prevent “good” plants from getting established. It can be dug with a shovel or cut with a knife. If a lot of mullein plants are in the savanna, a more efficient approach is to spray them with oil-soluble triclopyr ester (Garlon 4). A brief “spritz” of herbicide in the center of the plant is all that it takes to kill it.
Discussion of the use of herbicides has been given above.
The purpose of this section is to present a systematic
summary of herbicide use in savanna restoration.
Several herbicides are well suited for use in weed and
brush control in oak savannas. The herbicides discussed
here have been carefully established to be safe and
effective if used properly. Before using any herbicide,
it is essential that the label be read completely and
its specifications followed.
Herbicides are used to facilitate restoration in prairie
and savanna ecosystems in conjunction with other methods,
including hand pulling, mowing, cutting, prescribed
burning, seeding, and cultivation. Herbicides should
be used as part of an integrated weed management strategy.
The precise treatment method used will depend upon the
target species, its life history, the extent of the
problem, and the compatibility of the herbicide with
the restoration objectives.
The discussion here deals only with non-aquatic habitats.
Some herbicides are approved for use in aquatic habitats,
but the kinds, uses, and requirements are different.
Spot spraying and broadcast
For most herbicide applications in oak savannas, spot
spraying is preferred. This permits application of the
chemical just to the target species. Foliar application
should be made with a low-pressure (20-50 psi) backpack
sprayer equipped with a wand applicator. A sprayer nozzle
which creates a flat or cone-shaped pattern is preferable.
The herbicide should be allowed to dry for at least
two hours to ensure adequate absorption. (Do not spray
when rainfall is threatened.) Addition of a nonionic
surfactant to the mixture helps ensure complete leaf
coverage and increases the rate of absorption. The herbicide
should thoroughly cover the foliage but not to the point
of run-off. Personnel applying herbicide must be properly
trained and knowledgeable about the native vegetation.
Broadcast spraying is used primarily when a site is
to be completely killed because there is nothing “good”
there. In oak savanna restoration, this approach would
be used when planting understory vegetation on a former
pasture with large open-grown oaks. Since the pasture
grasses are almost certainly exotic cool season grasses,
they must be eliminated. It must be ascertained first
that all of the existing vegetation is undesirable.
The field can then be treated with a nonspecific herbicide
such as glyphosate, which kills all existing vegetation.
Since the scattered oaks make it impossible to spray
with a boom sprayer, an alternate procedure must be
A small utility vehicle capable of holding a 100 gallon
tank of herbicide and a long hose can be used. The hose
is connected to an electrical pump with a hand-held
spray nozzle. The electrical pump is controlled by a
pressure valve. An operator on foot operates the nozzle.
(With the proper pump and controller it is possible
for more than one operator to work at the same time.)
The site is marked into swaths and the operator moves
across the unit, directing the spray nozzle at the vegetation
and ensuring complete coverage. Although time consuming,
this approach is very effective in eliminating all cool
season exotic grasses.
of characteristics of some selected herbicides
monocots, including grasses
in soil 7-10 days; safe for aquatic uses
grasses, forbs, vines, trees, shrubs
residual; iinactivated by soil particles
herbs, sedges, woody plants
in soil 4-5 days
3A and 4
herbs and woody plants
monocots, including grasses
in soil 30 days
in soil 40 days
plants less affected
degradation and high binding to soil particles
some broadleaf species
in soil several months
information on each of the above herbicides can be obtained
from its label. The term “label” here is a misnomer,
because the label is generally a multi-page booklet.
The complete label for the herbicides listed above can
be obtained from the manufacturer’s web site, usually
as a PDF file. For all these herbicides, the label should
be read and followed!
It should be emphasized that herbicide use should be
part of a total management system. As the table shows,
none of these herbicides is completely specific. Care
must be taken to ensure that sensitive non-target species
are not treated.
Outline of procedures for herbicide use
• Herbicide label directions must be carefully followed.
• Protective gear should be worn as per the label directions.
• Herbicides must be labeled and stored appropriately,
and used containers must be disposed of properly.
• Empty containers should be rinsed at least three times
with clean water and the rinse water must be disposed
of per Environmental Protection Agency (EPA) guidelines.
• If an herbicide is used in a public area, notices
must be posted near all treated areas.
• Livestock should not be permitted in treated areas
until the herbicide has dissipated.
• Wind speeds must be less than 10 mph to minimize herbicide
• Areas to be treated should be surveyed first to ensure
protection of non-target species. Only spot applications
should be used in areas containing sensitive plant species.
• Personnel who function as commercial herbicide contractors
must be certified.
Examples of herbicide use for invasive plants
• 2,4-D. This herbicide is widely used for weed control
in lawns and other urban settings. It is active against
broadleaf plants (dicots) only; grasses are unaffected.
In natural areas., 2,4-D can be used for spot spraying
broadleaf weeds such as wild parnsip. However, if there
are desirable broadleaf species nearby, hand pulling
• Glyphosate is a broad-spectrum herbicide and kills
virtually all plants. Within a few days after spraying
the plants start to wilt and brown up. Widely used for
cut stem treatment of woody shrubs (but see Section
on Woody Shrubs above). The chemical moves to the roots
and kills the root system.
• At approved concentrations, sethoxydim is active only
against grasses; neither sedges nor broadleaf plants
are affected. It has been found effective in the control
of reed canary grass.
• Triclopyr is widely used for the control of woody
vegetation. Like glyphosate, it can be used to treat
cut stems to prevent resprouting. One chemical form,
Garlon 4, is soluble in oil and can be used to control
woody vegetation by basal bark treatment (see above).
• Clopyralid is unusually effective against plants of
the legume and sunflower families. It is used for the
control of legumes such as crown vetch and black locust,
and of composites such as Canada thistle and spotted
• Fosamine is used for control of woody plants such
as brush and brambles in noncropland areas. It is applied
as a foliage treatment during the growing season. Treated
woody plants remain green for the remainder of the growing
season but fail to leaf out the next spring. Only the
foliage sprayed will be affected, and other parts of
the plant will remain alive.
• Imazapic will control most broadleaf weeds as well
as cool-season grasses such as smooth brome and quack
Properly used, herbicides have wide utility in elimination
of invasive plants and the restoration of natural areas.
For specific recommendations, consult the herbicide
label or use the manufacturers advice.
Brush piles are often created during the management of prairie
and savanna restorations. Such brush piles frequently present
problems during prescribed burns if they have not been properly
located. The intense heat from a burning brush pile can kill
or cause serious damage to nearby trees. A burning brush pile
can often cause spot fires well outside the burn unit.
Brush piles that have been on the ground for some period of
time are extremely flammable and during prescribed burns may
get ignited by flying embers even when they are well outside
Rotten logs and stumps which are rather porous are often prone to ignition via glowing embers (spot fires), even though leaves and sound wood are resistant. Why is this so? Sound wood conducts heat so effectively that the heat from a burning ember spreads out quickly, effectively putting the fire out. On the other hand, porous fuels such as punky wood conduct heat poorly, so that the heat of an ember remains on the surface where it can cause ignition. Although they do not flame, these porous fuels can achieve glowing ignition from a relatively modest input of heat. Once ignited they can smolder for weeks, with the possibility of being fanned into flames by dry winds.
How are brush piles created? Many undesirable trees are cut
during savanna restoration, producing lots of wood. Downed trees
are occasionally arise as a result of windthrow. Brush piles
are also created in many tree removal operations. Removal of
invasive woody shrubs produces much wood, which is most easily
disposed of by burning in a brush pile.
How to avoid problems? Try not to create brush piles in the
first place. If conditions are suitable, burn the wood as it
is being cut. Start a fire with a small amount of downed dry
wood, and feed this fire as cutting proceeds. Ideally, this
approach should only be used when snow is present. In the absence
of snow, clear a wide stick- and leaf-free zone around the pile
to ensure that the fire does not spread. In some areas and at
certain times of year, depending on the governmental unit, a
permit may be needed to burn a brush pile.
Build brush piles well away from any living trees. A large pile
should be at least 10 feet (preferably farther) from any desirable
trees. Look up to be sure that limbs are not hanging over any
part of the pile.
In addition to living trees, brush piles should be constructed
well away from dead trees. Although standing dead trees are
great bird habitat, they are serious hazards in prescribed burns.
To keep them from igniting, brush piles that may burn should
be placed far away.
Build as few brush piles as possible. A few large piles are
easier to manage than many small piles. However, to avoid high
flame lengths, brush piles should be no more than 10 feet high.
Build brush piles into compact structures. Loosely constructed
piles are difficult to ignite.
If a brush pile is inside the burn unit, it should be at least
20 feet from any fire breaks. The taller the pile, the farther
it should be built from the fire break.
A newly created brush pile will not burn well. Wait at least
six months before burning it. If it must be burned right away,
then do not make a brush pile but burn the wood as it is being
cut, using drip-torch fuel to ignite the pile.
As soon as snow is present, burn all remaining piles. Do not
delay, as snow cover may not last.
Igniting brush piles. If the pile is very dry, ignition is easy.
For piles of freshly cut material, liquid fuel is needed. Drip
torch fuel (2 parts diesel, 1 part regular gasoline) works well
and is relatively safe, although there is a slight danger of
flashback. An alternative is diesel alone, with a butane torch
to ignite the diesel. Instead of a butane torch, a propane torch
such as is used for killing weeds can be used. This has a long
wand, so that the operator is well away from the igniting pile.
It is preferable to burn brush piles early in the winter than to wait for possible
snow (which may not come). The best time to burn is on a day
with a light misting rain. (Use liquid fuel to aid in igniting.)
Another way to burn in the rain is to keep the pile dry by covering
it with a waterproof cover. Remove the cover at the time of
ignition. Burning in very dry weather should be avoided. Adequate
personnel must be available to monitor piles. Clear a leaf-
and stick-free zone around each pile to ensure that fire “creep”
does not occur. Have a water can available just in case.
Ideally, there should be no brush piles remaining inside burn
units at the time of ignition.
If piles are still present at the time of ignition, two possibilities
exist. They can either be allowed to burn as part of the fire,
or they can be protected from burning. Provided they have been
properly constructed (away from living trees, well inside burn
units, etc.) it is preferable to let them burn. However, a large
burning brush pile is a potential hazard, since it produces
intense heat and sparks that may fly well outside the burn unit,
causing spot fires.
Protecting a large dry brush pile from burning when it is inside
the burn unit is difficult, sometimes impossible, especially
when it is very dry. Two things must be done: All fuel within
a six feet radius of the brush pile should be removed. During
the burning process itself, a black line must be created around
the brush pile. To create such a black line, an adequate supply
of water is essential to keep the fire contained.
• Create a limited number of well-constructed brush piles
• Construct them well inside burn units.
• Construct them well away from trees.
• If possible, burn all brush piles separately from the prescribed
• Protect living trees from burning brush piles