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; 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.

However, this approach is fairly expensive, since it must be contracted out. It is not suitable for use by volunteers.

A less expensive approach is to cut the woody plants with a brush cutter (we prefer Stihl) and treat the cut stems with 20% glyphosate. This approach is very effective, but since a single brush cutter can lay waste to quite a large area, at least two or preferably three people are needed to follow with spray bottles.

A low-tech approach to control of woody plants is to cut them with hand loppers and treat the cut stumps with 20% glyphosate. A hand-held spray bottle is used and the herbicide is confined just to the top of the cut stump. A single person can perform both tasks.

Although it is not much faster, a backpack sprayer can be used to treat the cut stems, thus avoiding the need for stooping.

The role of fire in brush removal Controlled burns are an essential component of any brush-control activity. Even if all undesirable brush is removed from an area, new growth will occur in the following seasons, and without further action the habitat will be degraded again. Although fire is an important part of an integrated approach to management of invasive brush, by itself is not enough.

Controlled burns will usually top-kill seedings or small shrubs, but the plants are not eradicated. It is essential, especially in savannas, to return to restored areas periodically (at least once every three years, or even annually in the first few years).

Eventually, newly established native grasses and forbs will begin to outcompete the shrubs. At the same time, these grasses and forbs will provide fuel for hotter fires which will kill the new growth of shrub seedlings. With continued use of herbicide on cut stems, and annual burning, the invasive shrubs should eventually be wiped out. Once these shrubs have been eliminated, fire can be used less frequently. In the long run in fire-dependent ecosystems, fire will be used for other purposes, and newly invading shrubs will be controlled at the same time.

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 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 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 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. (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.

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