Bush Honeysuckle: How It Changes the Forest Understory
Bush honeysuckle does more than fill space beneath the trees. Dense stands can change when light reaches the forest floor, which seedlings survive, and what the next forest looks like.
Photo: WXchaser / Wikimedia Commons · CC0 1.0 public domain dedication
Walk through a hardwood forest in late fall and bush honeysuckle can make itself obvious. The canopy may be thinning out. Native shrubs are fading. Yet a wall of green can still sit shoulder-high beneath the trees, often dotted with red berries.
That long green season is not just an identification trick. It is part of the ecological advantage.
In forests across the Ohio Valley, invasive bush honeysuckles can occupy the layer between the canopy and the ground so completely that the woods still look wooded while the understory is being simplified underneath. The mature trees may be standing. The change shows up first in the plants trying to live below them: wildflowers, native shrubs and, importantly, young trees that would eventually replace the canopy.
Several nonnative Asian bush honeysuckles invade Midwestern forests, with Amur honeysuckle (Lonicera maackii) among the best studied. These shrubs leaf out early, hold leaves late and can form a dense midstory that competes strongly for light.
Research from southwestern Ohio has found substantially lower plant richness, cover and tree-seedling density beneath Amur honeysuckle crowns. Newer Kentucky work shows the other side of the story: when honeysuckle is controlled, native herbaceous cover and species richness can rebound, but keeping it out is usually a continuing management job rather than a one-day cleanup.
The concern is not that every invaded forest suddenly loses its mature trees. It is that repeated failure beneath those trees can slowly change which plants are available to build the forest that comes next.
Which honeysuckle are we talking about?
“Honeysuckle” covers more than one plant, which is where conversations about control can get messy. This report is about the invasive Asian bush honeysuckles, especially Amur honeysuckle. It is not about every member of the honeysuckle family, and it is not the same growth form as Japanese honeysuckle, the familiar invasive vine.
University of Kentucky forestry guidance identifies Amur honeysuckle as the most common invasive bush honeysuckle in Kentucky, along with Morrow’s, Tatarian and Bell’s honeysuckle.3 In Indiana, all four are listed under the state’s Terrestrial Plant Rule. Indiana also lists Japanese honeysuckle separately.1
The shrubs are easier to notice during the parts of the year when much of the native vegetation is not fully green. Purdue Extension notes that invasive Asian bush honeysuckles tend to leaf out early and retain leaves late into fall. Opposite leaves, red fall berries and hollow pith in smaller stems are common identification clues.2
It takes the forest’s shoulder seasons
A deciduous forest runs on timing as much as space. Before the canopy closes in spring, sunlight reaches the ground in a brief pulse. That window helps spring wildflowers grow, native shrubs get started and young trees build leaves before shade deepens.
Amur honeysuckle can get there first.
A 2025 study at the University of Kentucky’s Robinson Forest found that Amur honeysuckle thickets greened up about a month earlier than uninvaded forest stands during the 2023 season, around mid-March instead of mid-April. The study was conducted in eastern Kentucky, so that timing should not be treated as a measurement for every LWR county. What it demonstrates clearly is the mechanism: honeysuckle can use an early-season light window before the native tree canopy is fully active.6
The same general advantage appears at the other end of the growing season when the shrub can remain green after many native plants begin shutting down. More days with active leaves means more time capturing light in a place where light is already the limiting currency.
Honeysuckle can become photosynthetically active before much of the native canopy and understory.
Dense stems and foliage occupy the midstory and intercept light that would otherwise reach lower plants.
Native herbs, shrubs and tree seedlings spend more of the growing season under competition.
If fewer seedlings survive and grow, the effect can carry forward into future forest structure.
Shade is the obvious effect. Regeneration is the bigger one.
Dense honeysuckle looks like a shading problem because that is the part anyone can see. Research suggests the consequence goes deeper than a darker forest floor.
In a frequently cited 2002 study of southwestern Ohio forests, plots directly beneath Amur honeysuckle crowns had lower plant richness and abundance than nearby plots away from the shrubs. Across the study, overall species richness was 53% lower beneath honeysuckle crowns, total plant cover was 63% lower and the density of tree seedlings capable of reaching the canopy was 68% lower.4
What one southwestern Ohio study found beneath Amur honeysuckle crowns
These figures compare small plots beneath honeysuckle crowns with plots away from the shrubs. They describe this study, not every invaded forest.
Source: Collier, Vankat & Hughes, 2002.4
A separate field experiment tested competition more directly by removing honeysuckle shoots, trenching around tree seedlings, or both. Above-ground competition was generally more important than below-ground competition for the survival of the native seedlings tested.5 That points back to the thing a dense thicket does exceedingly well: occupy the light environment.
This does not mean every missing seedling was killed by honeysuckle. Deer browsing, drought, soil conditions, canopy density and other invasive plants also shape regeneration. Forests are rude enough to resist single-cause explanations. But when multiple studies show poorer understory performance associated with honeysuckle and experiments improve conditions by removing its above-ground competition, the light-and-competition mechanism is hard to dismiss.
The easy “poisoned soil” story is too simple
Amur honeysuckle contains chemical compounds that can affect other plants, and laboratory work has found inhibitory effects on seed germination. That has led to a common shorthand: honeysuckle “poisons” the ground.
The evidence is more complicated than that sentence.
Experimental studies support allelopathic potential, meaning chemicals released by the plant can inhibit some other species under some conditions. But the response varies by the target plant, the material being tested and the experimental setup. A multi-assay study found mixed, species-specific responses and explicitly called for more work to establish how important those effects are in field environments.7
“Honeysuckle poisons the soil, so nothing else can grow.”
Honeysuckle strongly alters competition and light. Chemical effects may add to that pressure, but their field importance is more context-dependent.
For a land manager, the distinction matters. If the problem were simply a toxin left in the soil, removing the shrub would not be expected to produce much recovery. Yet field studies have documented increases in native or herbaceous vegetation after control. That is good evidence that freeing light and growing space can matter quickly, even while soil processes and seed banks continue to influence what comes back.
The next forest is what is at stake
Understory change can feel minor beside a 70-foot oak. It is not.
Forests replace themselves from below. Seedlings survive in shade, wait for small openings and respond when storms, disease, timber harvest or simple old age remove trees above them. When that layer is thin or dominated by species that will never become canopy trees, succession has fewer options.
This is why bush honeysuckle belongs in the same conversation as deer browsing, invasive groundcovers and other pressures on forest regeneration. It does not have to kill a mature tree outright to change the trajectory. It can make the recruitment stage harder, year after year.
The issue is especially relevant across the LWR region because invasive plants rarely arrive alone. A woodland edge can hold bush honeysuckle above and Japanese stiltgrass across disturbed ground below. Those species use different parts of the understory, but the management problem starts to rhyme: native regeneration is competing for fewer openings.
Removing honeysuckle changes habitat too
There is a fair question here. If birds use a honeysuckle thicket for cover, does removing it automatically improve wildlife habitat?
Not on the first afternoon.
A 2025 Iowa study looked at forest-breeding birds 4 to 5 years after aerial herbicide treatment reduced Amur honeysuckle. Native plant cover and species richness were greater in treated stands, but some bird groups were more abundant in untreated stands. The authors warned that short-term declines can occur for some understory-associated birds and recommended pairing honeysuckle removal with native shrub restoration when possible.9
That study was in Iowa, not southern Indiana, Illinois or Kentucky, so it is evidence of a management tradeoff rather than a local bird census. Still, the lesson travels well: vegetation structure has value even when the species providing it is invasive.
The goal of restoration is not to turn a dense shrub layer into bare woods and declare victory. It is to move the understory toward native structure that can continue providing cover, browse, nesting substrate and regeneration without allowing honeysuckle to keep controlling the layer.
Removal is the start of restoration, not the end
A 2026 central Kentucky experiment gives this part of the story unusually current regional evidence. Researchers compared untreated Amur honeysuckle plots with plots where honeysuckle was removed using cut-stump treatment, and with removal plots that also received wildrye and northern spicebush plantings.
Over time, the removal treatments had greater herbaceous cover, less bare ground and higher species richness than untreated plots. The extra restoration planting treatment, however, did not significantly reduce honeysuckle reinvasion or improve the measured plant-community variables beyond removal alone.8
That does not mean planting natives after removal is pointless. The spicebush portion of the experiment suffered substantial mortality, with deer browsing and drought among the problems the authors identified. It means restoration is site-specific and stubbornly real-world. Putting the right plant on paper is easier than keeping it alive through browsing, dry summers and another flush of honeysuckle seedlings.
The same study makes a more useful point for landowners: persistent management matters. Mature shrubs can produce a lot of seed, nearby infestations can keep supplying more and newly opened light can give surviving seedlings another chance.8
What management actually looks like
There is no single treatment that fits every infestation. A few scattered young shrubs are a different job from an acre of mature multi-stemmed honeysuckle. The condition of the native understory matters too. Heavy machinery may remove a thicket quickly, but it can also disturb soil and surviving native plants.
Small or young plants
Hand-pulling can work when the full root system can be removed and soil disturbance is acceptable. Purdue notes that young plants are often shallow-rooted, although apparent “small plants” can sometimes be suckers attached to a larger root system.2
Established shrubs
Cut-stump or basal-bark herbicide treatments are commonly used because simply cutting a mature shrub can allow resprouting. Product labels, site conditions, nearby water and non-target plants all matter.2
Timing
Late fall can make identification easier because invasive honeysuckle often remains green after many native plants lose leaves. That can also help reduce accidental treatment of dormant native vegetation in some control approaches.2
Anyone using an herbicide should follow the current product label and applicable state rules. Where a site contains sensitive plants, wetlands, steep slopes or extensive native understory, getting site-specific advice from a forester, extension specialist or invasive-plant professional is worth the phone call.
And in Indiana, remember that listed bush honeysuckles are regulated plants. Disposal and movement should not create the very spread the work is supposed to stop.1
What the evidence supports
- Invasive bush honeysuckle can change the understory long before an invaded forest stops looking like a forest.
- Its extended leaf season and dense shrub canopy give it a strong advantage in a light-limited layer.
- Southwestern Ohio research found markedly lower plant richness, cover and tree-seedling density beneath Amur honeysuckle crowns.
- Allelopathy may contribute to its effects, but the field evidence for competition and altered light is clearer than the simple claim that honeysuckle “poisons the soil.”
- Removal can improve understory vegetation, but lasting restoration usually requires monitoring what returns and treating reinvasion.
Common Questions
Is all honeysuckle invasive?
No. North America has native honeysuckles, and the name covers both shrubs and vines. Identification should come before control. This article focuses on invasive Asian bush honeysuckles such as Amur, Morrow’s, Tatarian and Bell’s.
If birds eat the berries, isn’t bush honeysuckle useful wildlife habitat?
Wildlife can use the fruit and the shrub structure. That does not erase the documented effects on native understory plants and regeneration. The practical restoration question is whether native shrubs and other vegetation can replace the cover and food functions as honeysuckle is removed, rather than treating “used by wildlife” as the same thing as “ecologically harmless.”
Will cutting bush honeysuckle kill it?
Not reliably. Established shrubs can resprout after cutting. Common control methods pair cutting with an appropriate cut-stump treatment or use another method designed to kill the root system. Always follow the herbicide label and site-specific rules.
Can native plants recover without replanting?
Sometimes. The 2026 central Kentucky study found greater herbaceous cover and species richness after honeysuckle removal even though added wildrye and spicebush plantings did not outperform removal alone on the study’s measured community variables. Recovery will depend on what native plants and seed sources remain, deer pressure, soil disturbance, competing invasives and weather.
When is bush honeysuckle easiest to spot?
Early spring and late fall are useful windows because invasive bush honeysuckles often green up before much of the native vegetation and stay green later. Red berries can also make mature shrubs conspicuous in fall.
References
- Indiana Department of Natural Resources. Terrestrial Invasive Species — Plants: Terrestrial Plant Rule. Accessed September 29, 2026.
- Grisham, J. (2025). Kill the Shrubs: A Guide to Fall Removal of Invasive Honeysuckle. Purdue Extension.
- University of Kentucky Department of Forestry & Natural Resources. FOR175 — Woodland Invasive Plant Management Series: Bush Honeysuckle.
- Collier, M. H., Vankat, J. L., & Hughes, M. R. (2002). Diminished plant richness and abundance below crowns of Lonicera maackii, an invasive shrub. The American Midland Naturalist, 147(1), 60–71.
- Gorchov, D. L., & Trisel, D. E. (2003). Competitive effects of the invasive shrub, Lonicera maackii, on the growth and survival of native tree seedlings. Plant Ecology, 166, 13–24.
- Liang, L., Yang, J., Wittenbraker, W. C., Crocker, E. V., Tomaszewska, M. A., & Henebry, G. M. (2025). Characterizing phenological differences of invasive shrubs in a forest matrix using high resolution VENµS time series. International Journal of Applied Earth Observation and Geoinformation, 136, 104333.
- McEwan, R. W., Arthur-Paratley, L. G., Rieske, L. K., & Arthur, M. A. (2010). A multi-assay comparison of seed germination inhibition by Lonicera maackii and co-occurring native shrubs. Flora, 205(7), 475–483.
- Ruffner, M. E., Cox, M., Wiley, E., Garland, A., & Shafer, W. (2026). Managing invasive Amur honeysuckle (Lonicera maackii) in central Kentucky: can native species release and restoration plantings hold their ground? Invasive Plant Science and Management, 19, e16.
- Fernald, K. M., Curzon, M. T., & Harms, T. M. (2025). Impacts of invasive honeysuckle removal on forest-breeding birds in western Central Hardwoods forests. Forest Ecology and Management, 123093.