Resurgence of Native Plants after Removal of Amur Honeysuckle from Bender Mountain Preserve, Ohio

Lonicera maackii (Amur honeysuckle) is an Asian shrub that was introduced to North America by Botanical Gardens in the 1890’s (Luken and Thieret 1996). The shrub produces red berries that are eaten by birds. The birds deposit the seeds in old shrub borders, hedges, wasteland and woodlands (Dirr 1983). The tendency of L. maackii to reproduce and spread beyond the point of initial planting was first recorded in archives of the Morton Arboretum near Chicago in the mid-1920’s (Luken and Thieret 1996). As early as 1961, E. Lucy Braun noted that L. maackii had escaped from cultivation in Hamilton County, Ohio (Braun 1961). Lonicera maackii forms dense thickets in the forest sub-canopy. It ultimately forms thickets so dense that little if anything can grow underneath them (Homoya 2012), not even tree seedlings. It alters habitats by decreasing light availability, by depleting soil moisture and nutrients, and possibly by releasing toxic chemicals that prevent other plant species from growing in the vicinity (Williams 1994). Eventually, invaded woodland habitats become areas covered with L. maackii in the shrub layer and few large canopy trees above the honeysuckle (figure 1).

Bender Mountain Nature Preserve (39.10° N, 84.67° W) is a 22.3 ha preserve in Hamilton County, Ohio, consisting of property owned by Delhi Township Parks and Recreation, as well as land owned by the Western Wildlife Corridor. The preserve is managed by the Western Wildlife Corridor, a land trust dedicated to preserving the environmental heritage of the Ohio River Valley (www.westernwildlifecorridor.org). As a result of glaciation, Bender Mountain Nature Preserve encompasses many different ecosystems including steep slopes, narrow valleys, dry rocky ridge tops, warm fertile south facing slopes, cool fertile north slopes, alluvial benches, springs, wet seeps, and riparian zones. These different habitats support a diversity of plant species including the uncommon Collinsia verna (blue-eyed Mary) that grows in profusion on the gentle slope above Rapid Run creek; Quercus rubra (northern red oak), Carya ovata (shagbark hickory), Oxalis grandis (great yellow wood sorrel), Saxifraga virginiensis (early saxifrage), and Danthonia spicata (poverty oat grass) that prefer the upper slopes; and Scirpus spp. (bulrushes), Impatiens spp. (jewelweeds), Equisetum spp.(scouring rushes), and Lobelia siphilitica (great blue lobelia) that prefer wetter areas.

Throughout the time of Native American and pioneer settlement, the steep slopes prevented intensive agriculture, permitting plant populations to endure. Then a threat arrived that could have decimated the plant communities—invasive plants. By the year 2000, L. maackii covered most of Bender Mountain with a blanket of foliage that blocked the sun (figure 1). The non-native invasive Alliaria petiolata (garlic mustard) which is shade tolerant, was also gaining a foothold.

When Western Wildlife Corridor began managing the preserve in 2004 we developed a plan calling for the removal of L. maackii, A. petiolata, and other invasive plants as they appeared. The result was control of the invasives so that Bender Mountain Preserve now has hundreds of native plant species, none of which were planted (Conover 2016).

Figure 1.

Lonicera maackii (Amur honeysuckle) forming a dense shrub layer beneath the tree canopy in a wooded area at Bender Mountain Nature Preserve, Hamilton County, Ohio. Photo credit: Tim Sisson.

To accomplish the removal of L. maackii we used a multi-task approach involving foliar spraying with an herbicide, cutting of the plants and physically removing the plants. Foliar spraying is an effective way of eliminating invasive plants and it is less time consuming than cutting or pulling. For foliar spraying of L. maackii we used a mixture containing 2% glyphosate (183 mL Drexel Imitator Plus per 3.8 L of water). Amur honeysuckle leafs out earlier and holds its leaves longer than native trees and shrubs (Luken and Thieret 1996). Foliar spraying of Amur honeysuckle can occur on warm days in the fall after native trees and shrubs have lost their leaves (Conover and Geiger 1993, 1999).

For larger L. maackii we cut them off close to the ground and immediately...