Honeysuckle (species of Lonicera) is a nonnative plant that is a major threat to Wisconsin's woodlands.

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An area heavily infested with honeysuckles. In such areas, there may be dozens of such bushes covering the natural area. The shade they produce is so heavy that native forbs and grasses are unable to flourish.

There are several species of honeysuckle that cause problems in Wisconsin natural areas, but there is no reason to classify them since they are all nonnative and they are all bad. The native honeysuckles in most of Wisconsin can easily be distinguished from the bad ones because the natives are mostly woody vines rather than bushes. The exception is in northwestern Wisconsin where the native fly honeysuckle is an abundant understory shrub in wet mesic sites.

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 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.

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. The ground under a honeysuckle patch is often completely bare. In order to reintroduce fire, it is essential first to eliminate the honeysuckles and then reseed with native plants, preferably seed mixtures containing grasses such as Indian grass or bluestem that will carry a fire.

Close up of honeysuckle flowers. In southern Wisconsin, flowering occurs in late April or early May

Control of honeysuckle

Both mechanical and chemical methods must be used together on honeysuckle. 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. Concentrated glyphosate, such as Roundup Ultra, is around 40% out of the bottle, so that a 20% solution can be made by mixing equal parts of glyphosate and water. (Some sources recommend lower concentrations of glyphosate, but with the higher concentration resprouts are less likely to occur.)

Honeysuckle can be cut with either a brush cutter or a hand lopper. The hand lopper works well and is suitable in volunteer work parties, because each volunteer can participate in cutting. If a stem is too large to cut with a lopper, a handsaw can be used. With a brush cutter, it is important that the cutting blade be sharp. With a dull blade, the cut stems are often shredded and splintered, making them harder to treat with herbicide. For the largest stems, a chain saw may be necessary. No matter which cutting method is used, it is essential that the stumps be cut sharp and straight across, so that the cut stumps can be treated with herbicide (as described below).

The tools of the honeysuckle trade. Hand loppers, a spray bottle containing 20% glyphosate and a red dye, and persistence.

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 company.)
• 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 covered with the dye/herbicide mixture.

With practice, this procedure works quite well and the honeysuckle plants should not resprout. Note that with this procedure, the herbicide is confined only to the cut stumps and is not spread around the environment.

Research has shown that in southern Wisconsin honeysuckle can be cut at any time of the year. Winter is an excellent time to cut, and glyphosate works quite well then.

Honeysuckle is very persistent, and will resprout readily if not treated with herbicide.

Please note: There is no point in cutting honeysuckles if they 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 are 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 honeysuckles have been eliminated from a natural habitat, they can usually be kept out by controlled burning. Remember, there will be a seed bank, so that small honeysuckles will appear next year. If the habitat is not burned, these small honeysuckles will grow big and you will have the same problem again. Once established, native grasses will carry a fire and help keep the honeysuckle seedings in check.

Please note: Eradication of honeysuckle should not begin until an approved burn plan has been developed. For the first few years after removal of honeysuckle from an area, annual burning is recommended, so that the new seedlings are destroyed.