Brush
Control
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
from fire.
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
bramble monocultures.
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
oak woods.

Honeysuckles
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
a habitat.
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.
Honeysuckle
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
up.
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
of weeds.
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
new growth.
Buckthorn
Common buckthorn (Rhamnus cathartica)
has been a serious invader of the oak savanna areas at Pleasant
Valley Conservancy. It is a small tree or shrub and can reach
a height of 20-25 feet. Buckthorn has a characteristic orange
inner bark which provides a good way of identifying it. The
outer bark is dark gray or brown, and when cut the inner bark
is brown, red, or orange.
Buckthorn has separate male and female plants; the latter
are often easy to recognize because they produce copious amounts
of deep purple berries. It is especially important to remove
the berry-producing plants, because they will otherwise be
a constant source of infection for the area.
Buckthorn is of Eurasian origin and 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
Wisconsin.
Many bird species relish buckthorn berries. However, the
berries contain a chemical which acts as a laxative (hence
the species name cathartica). The defecation by the
birds insures the spread of the seeds throughout the habitat.
Since female trees may produce abundant fruit, within a few
years there can be thousands of buckthorn seedlings in the
area of a mature tree. Buckthorn seeds are able to remain
alive in the soil, and new seedlings will continue to appear
for years after the plants have been removed from an area.
Early identification, before seed production has started,
is vital. Small buckthorn seedlings can be readily removed
by hand pulling. However, this mechanical removal disturbs
the soil and encourages reinfestation or colonization of other
weeds so that loose soil should be tamped down to make a firm
surface.
Herbicides for buckthorn control There
are several herbicides that are very effective in control
of buckthorn. One of the most effective is triclopyr (Garlon;
Dow Agrochemical). An effective way to control buckthorn is
by the use of basal bark treatment with Garlon in oil. This
is best done in winter, when native vegetation has all died
back and will not be affected. A concentration of 12-15% triclopyr
(active ingredient) in diesel fuel or kerosene is recommended
by the manufacturer. Use the herbicide in a backpack sprayer
(see photo above) with a nozzle that produces a solid cone
or flat fan spray. Spray the lower part of the trunk in such
a manner that it becomes thoroughly wet, including the root
collar, but not to the point of runoff. Each stem of the plant
must be treated. Properly done, this basal bark treatment
is extremely effective and the plant will not leaf out the
following growing season. 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 below is preferable.
Cut stump treatment Another very effective
way of eradicating buckthorn is to cut the plant just above
the ground level (hand lopper, brush cutter, or chain saw)
and treat the cut stump with 20% glyphosate. Glyphosate is
the preferred herbicide because it is inactivated by soil
particles so that there is no residue in the soil. It should
be emphasized that cutting buckthorn without herbicide
treatment should never be done, because the cut plants
will resprout heavily from the roots, leading to a situation
that might be worse than if the plant had not been cut at
all. It is useful to include a blue or red dye in the herbicide
mixture so that the cut stump treatment can be monitored.
A backpack sprayer or hand spray bottle can be used. Be sure
that the stump is thoroughly wetted with herbicide. This procedure
is economical of herbicide and confines the chemical to the
stump itself, but is more labor-intensive than basal bark
treatment. However, it has the advantage that the buckthorn
plants themselves are being removed from the habitat.
Although the cut stump procedure can be used at any time
of the year, the winter is preferable because nontarget plants
are not affected. This procedure is effective with plants
of any size, even large ones. Remove all the cut material
to a pile for subsequent burning.
Brambles
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
established.

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.

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