Bush Honeysuckle
Bush Honeysuckle (Lonicera maackii), also known as Amur honeysuckle, is one of the most destructive invasive species in the St. Louis region. The Garden recently created a new bush honeysuckle brochure to increase public awareness of this issue and encourage citizens of our region to take notice and take action. This page on invasive bush honeysuckle provides complimentary information for the brochure, including expanded content on its origins and impacts, detailed instructions for control, native plants that are similar in appearance, and suggested landscaping alternatives.
 
Honeysuckle History

Bush Honeysuckle Removal and Control

When: Bush honeysuckle can be removed any time of the year. However, early spring and late fall are ideal for locating and removing this invasive shrub, since it has leaves when our native shrubs and trees do not. Once you develop an eye for the yellowish-green leaves of bush honeysuckle in late fall, this time of the year is ideal for detecting isolated shrubs and removing them before the infestation expands.

How: There are multiple effective methods of removing bush honeysuckle. Selecting the right approach depends upon a number of factors, such as the area covered by the invasion, the size of the plants to be removed, and your personal capabilities and preferences. These instructions are intended to provide homeowners and volunteers information necessary to take action against bush honeysuckle. Some additional methods for controlling large-scale infestations used by professional contractors and conservation organizations with highly specialized equipment and experience are not addressed.

Cut Stem Application*

The most effective and efficient method of removing larger bush honeysuckle plants is to cut the stem as close to the ground as possible and immediately apply an appropriate herbicide after cutting. Don’t cut stems too fast and loose track of them before treating them with herbicide. Any stems that are cut without herbicide treatment will vigorously resprout, so it is important to treat stems promptly after cutting. When doing cut-stem treatments, safety precautions must be taken for both cutting and the herbicide treatment. Always follow the herbicide label and use required personal protective equipment. It may be intuitive that non-chemical removal methods such as digging are less harmful to the environment than any approach that incorporates herbicides. However, digging up large bush honeysuckle plants in natural areas causes extensive soil disturbance, which can damage non-target plants, increase erosion, and create optimal conditions for recolonization by bush honeysuckle and other invasive plants. The methods suggested below describe the very precise application of herbicides with low environmental persistence and toxicity, resulting in the effective control of bush honeysuckle without soil disturbance or damage to non-target vegetation. 

Cutting Tools: The best tool for cutting bush honeysuckle depends upon the size of the plants being cut and the size of the area being treated. Appropriate tools range from hand pruners, lopping shears, and folding saws to chainsaws and brush blades. Only use tools with which you are comfortable and experienced, and always use personal protective equipment.

Herbicide Type: The most frequently recommended herbicide for controlling bush honeysuckle with cut-stem application is glyphosate, because it is effective and has low environmental persistence and toxicity compared to other herbicides (22). Although the herbicide product Tordon RTU is also highly effective for cut-stem application control of honeysuckle (23), one its active ingredients, picloram, persists in the environment and can harm non-target terrestrial and aquatic plants.

Glyphosate is the active ingredient in many common broad-spectrum herbicide products. Although the chemical glyphosate itself has low toxicity, some surfactants (chemicals that increase herbicide adhesion to leaf surfaces) added to glyphosate herbicide products are highly toxic to aquatic organisms (24). For this reason, it is important that only glyphosate formulations approved for aquatic use are used near water (e.g. Rodeo, AquaMaster, AquaPro, and others).

Herbicide Concentration: An herbicide solution containing approximately 20% active ingredient of glyphosate is recommended for cut-stem application control of bush honeysuckle. Mixing a small amount of spray indicator dye (either blue or red) into the solution is helpful for keeping track of which cut-stems have been treated.

The herbicide glyphosate is the active ingredient in a vast array of herbicide products, ranging from ready-to-use foliar spray formulations that contain only 2% glyphosate to concentrates containing 50% glyphosate. The most widely available concentrates usually contain 41% active ingredient of glyphosate. Although label instructions recommend applying concentrates undiluted for cut stem application, studies have shown that a 20% active ingredient solution (1 part concentrate mixed with one part water) is highly effective for controlling bush honeysuckle (25, 26). Although mixing a 20% active ingredient solution of glyphosate from concentrate is recommended, Roundup Concentrate Poison Ivy Plus Tough Brush Killer (18% glyphosate and 2% triclopyr salt) is a ready-to-use herbicide product that is also effective for cut-stem control of bush honeysuckle.    

Herbicide Application Methods: Herbicide is only applied to the outer edge of the cut-surface, the cambium, which contains the plants vascular tissue (for an illustration, see figure A in from this informational brochure).

Various tools are often used for cut-stem application, such as spray bottles and paint brushes, which can be somewhat messy. However, one of the easiest methods for cut-stem herbicide application is a Nalgene drop- dispensing bottle, which very precisely applies herbicide directly to cut stems and won’t leak even when turned upside down. Such precision and cleanliness assures that herbicide is not accidentally applied to non-target vegetation, and also prevents accidental herbicide contact for the person treating cut stems. Small 2 ounce bottles are available locally at REI. Depending on the pace of work and the number of plants to be treated, a 2 ounce bottle may be adequate. However, a bigger bottle is more appropriate for extensive work, and 8 ounce bottles can be purchased online. If the tip of the dispensing bottle gets clogged with fine debris, it can be cleaned with warm water. Clogs can also be cleared in the field by poking the interior of the dispensing aperture with a safety pin, but this will unavoidably widen the aperture. Using a drop dispending bottle with a widened aperture is still very precise and allows for a faster flow rate, which some users prefer, but the bottle will no longer be leak-proof if it is turned upside down without the cap in place. Wrapping a strip of neon orange duct tape around the dispensing bottle is helpful to avoid losing sight of the bottle in leaf litter. 

* A Note About Herbicides: The judicious use of herbicides is often the most effective means of controlling invasive species, but careless or uneducated herbicide use can result in collateral damage to non-target vegetation and other ecological harm. Although the Missouri Botanical Garden does not explicitly endorse the use of any herbicide product, it is important that homeowners who chose to use herbicides understand correct application practices. Always follow the herbicide label and use required personal protective equipment.

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