Foliar Spraying with Glyphosate Kills Invasive Five-leaf Aralia in a Wooded Natural Area (Ohio)

Eleutherococcus sieboldianus (five-leaf aralia) is a commonly cultivated arching, prickly shrub from Asia that produces berries and sometimes escapes from cultivation (Lamont and Young 2002, Voss and Reznicek 2012, University of the District of Columbia 2016, Invasive Plant Atlas 2015, Bravo et al. 2012). In addition to flowering and producing small black berries with two to five seeds each, it can spread quickly by forming new roots when branches touch the ground. It is a rapidly growing deciduous shrub which can quickly displace native plants (National Park Service 2012). Eleutherococcus sieboldianus is widely planted for landscaping. It is considered to be one of the toughest shrubs available (Dirr 2011), but it is highly threatening to natural plant communities. Therefore, all detected occurrences in natural areas should be eradicated before it has a chance to spread further (National Park Service 2012, Central Jersey Invasive Species Strike Team 2016).

Figure 1.

Eleutherococcus sieboldianus (five-leaf aralia) in Burnet Woods Park.

Figure 2.

Glyphosate killed E. sieboldianus in Burnet Woods Park two months after spraying.

Eleutherococcus sieboldianus is now reported as an escape from cultivation in several eastern states (Invasive Plant Atlas 2015). In addition, E. sieboldianus has become adventive in Oxford, Ohio (Vincent et al. 2011) and at least three locations in Cincinnati, Ohio (Ault Park, Spring Grove Cemetery, and Burnet Woods Park). At one of these locations, Burnet Woods Park, a large patch of E. sieboldianus was discovered in May, 2014 growing within a wooded area inside the park (Figure 1). Southwestern Ohio is where the highly invasive Asian shrub Lonicera maackii (Amur honeysuckle) first became adventive in Ohio (Braun 1961). If L. maackii had been eradicated earlier, it might not be the big problem that it is today (Conover and Sisson 2016). To eradicate the E. sieboldianus plants at Burnet Woods before they had a chance to produce berries and spread further, in June, 2014 the leaves were sprayed with a 2% glypho-sate herbicide solution with an added surfactant (79.9 mL Honcho Plus and 14.8 mL dishwashing liquid per 3.8 L water). This was done on a warm, sunny day. A fine spray was used so little herbicide ran onto the ground, but most of the leaves were covered. Glyphosate is a non-selective herbicide that may kill or harm any plants that come in contact with the spray, so herbicide exposure of the buds, bark or roots of saplings of native trees and shrubs as well as native herbaceous plants was minimized.

Figure 3.

Glyphosate killed E. sieboldianus in Burnet Woods Park two years after spraying with native plants (Impatiens pallida) reclaiming the area.

Two months after spraying, 100% of the E. sieboldianus was dead (Figure 2). Two years after spraying (2016), the area was being reclaimed by native plants including Impatiens pallida (pale jewelweed [Figure 3]). Eleutherococcus sieboldianus could become a serious threat to native plants in natural areas. It should be eradicated as soon as possible if detected growing in a natural area. The plant has short spines found at each leaf bud along the stems which make it difficult to handle, but the plant can be effectively killed by spraying the leaves with a 2% glyphosate solution.

To lessen reinvasion and to restore native shrub and forest habitat, I recommend planting native shrubs and small native trees in the areas cleared of E. sieboldianus. Depending on location these planted species could include species such as Lindera benzoin (spice-bush), Viburnum prunifolium (black-haw), Corylus americana (American hazelnut), Staphylea trifolia (American bladdernut), Cornus drummondii (roughleaf dogwood), and Prunus americana (wild plum). In the Cincinnati area, deciduous woody plants are best planted in early spring while still dormant and when there will be plenty of moisture available during establishment.