Bush honeysuckle, primarily species like Amur honeysuckle (Lonicera maackii), is a fast-growing, deciduous shrub originally introduced to North America from Eurasia in the late 19th and early 20th centuries. It was initially valued as an ornamental garden plant, for erosion control, and as wildlife habitat. However, it is now recognized as a highly aggressive invasive species across much of the eastern and central United States. Its ability to rapidly colonize and degrade native ecosystems disrupts natural plant communities and has far-reaching negative consequences for local ecology.
How Bush Honeysuckle Dominates Native Plant Life
The primary mechanism of bush honeysuckle’s dominance is its extended photosynthetic period, which gives it an overwhelming competitive edge over native flora. It is one of the first shrubs to leaf out in the early spring, often weeks before native trees and wildflowers, and it retains its leaves into the late fall or early winter. This extended leaf presence effectively shades the forest understory. Native species, especially spring ephemeral wildflowers and tree seedlings, need sunlight during these critical times to complete their life cycles.
The shrub’s dense, multi-stemmed growth habit creates thick, nearly impenetrable thickets, physically crowding out diverse native vegetation. This aggressive growth allows it to form monocultures, significantly reducing the biodiversity of the plant community underneath its canopy. Bush honeysuckle also utilizes significant amounts of soil moisture, depleting water resources that native plants and tree seedlings require for establishment and survival.
Negative Effects on Soil and Water Resources
Bush honeysuckle causes damaging changes below ground by employing chemical warfare against its neighbors, a process known as allelopathy. The decomposing leaves leach various phenolic compounds into the soil, which inhibit the germination and growth of several native plant species. This chemical inhibition is a major factor in the shrub’s ability to maintain a monoculture where native plants cannot thrive.
The shrub also alters soil composition and nutrient cycling in the invaded areas. Honeysuckle leaves contain higher nitrogen levels and less lignin than many native trees, causing them to decompose more rapidly. This change in leaf litter decomposition rates increases soil nitrogen, which favors the continued growth of the invasive shrub while disturbing the nutrient balance required by native plants.
The establishment of dense honeysuckle thickets contributes to increased erosion potential, particularly along slopes and waterways. The shrub has a shallow root system, and its deep shade eliminates the diverse ground layer of native plants and leaf litter that anchors the soil. With the protective native understory gone, the bare soil between the stems is more vulnerable to sediment runoff, contributing to the pollution of local water bodies.
Harm to Local Wildlife and Food Webs
Bush honeysuckle produces abundant red berries in the fall, but the fruit offers poor nutritional value for many bird species, especially those preparing for migration. The berries are high in simple carbohydrates but significantly lower in fat content compared to native shrubs. Consuming this nutritionally deficient food source provides inadequate fuel for migratory birds, potentially jeopardizing their long-distance journeys.
The plant’s presence also starves the base of the food web by failing to support native insect populations. Since it did not co-evolve with North American insects, the shrub hosts far fewer native caterpillar and herbivore species. This lack of insect life directly impacts nesting birds, many of which rely on insects as the primary food source for their young.
The early leaf-out, which is advantageous to the shrub, proves detrimental to nesting birds that select it for shelter. Birds are often attracted to the early cover, but the dense, low-growing structure and foliage make nests more visible to predators. Studies show that nests located in honeysuckle fledge up to 20% fewer offspring compared to those in native shrubs, contributing to a decline in local bird populations.
Strategies for Control and Management
The control of established bush honeysuckle requires a multi-year commitment, as simply cutting the shrub causes it to resprout vigorously. Small seedlings and young plants can be removed through hand-pulling, especially in the early spring when the soil is moist. It is necessary to remove the entire shallow root crown to prevent regrowth.
For mature shrubs with stems greater than one inch in diameter, the most effective method is the cut-stump treatment. This involves cutting the shrub close to the ground and immediately applying a concentrated herbicide solution, often glyphosate, to the freshly cut surface. The herbicide must be applied quickly to the outer ring of living tissue on the stump. This ensures the plant transports the chemical down to the root system.
The best time for this treatment is during the late summer, early fall, or the dormant season, as the plant is actively moving resources to its roots, increasing the herbicide’s effectiveness. Alternatively, a non-chemical method involves cutting the stump low and covering it with durable black plastic. This deprives the stump of sunlight and prevents resprouting. Regardless of the removal method, follow-up monitoring is crucial. Native plants should be introduced afterward to restore the understory and prevent re-establishment.