The quarterly electronic newsletter of the
Southeastern Wisconsin Invasive Species Consortium
Autumn is a good time to effectively control many invasive shrub species. Glyphosate foliar application of herbicide is most effective in late summer or fall; after blooming, but prior to change in leaf color. Basal applications can be made any time of the year, but are most effective during the dormant season when leaves are not present.
Common buckthorn (Rhamnus cathartica)
Common or European buckthorn is native to Europe and was brought to Wisconsin as early as 1849 for use as a hedging plant. Due to its long distance dispersal ability (birds eat the berries), prolific seed reproduction, and wide-ranging habitat tolerance, buckthorn is quickly invading woodland understories and prairie edges. Diagnostic characteristics of buckthorn are the prolific black berry clusters, the leaves that stay green well into late fall, a notable false thorn at the end of the twigs, and yellow sapwood-made visible when cut. The bark is gray/brown and exhibits many lenticels (small white spots that function as pores). With large infestations, the female seed-producing plants should be removed first. Cut-stump treatments with 20-25% Glyphosate mixed with water or 12.5% Triclopyr mixed with bark oil should be applied to the cambium layer and down the side of the cut stump to the root crown. Cut-stump treatments can be applied anytime but are most effective in fall, and through the winter. Smaller plants can be hand pulled due to a shallow root system.
Non-native bush honeysuckle (Lonicera spp.)
There are multiple species of non-native honeysuckle that are out competing native plants in our natural areas. Once fully entrenched, non-native honeysuckle will form a dense thicket; creating a heavily shady forest floor that prevents almost anything from growing beneath it. Exotic honeysuckles have opposite, toothless, simple leaves and fragrant, tubular (white, pink, or red) flowers that bloom May-June. Although, honeysuckle can be treated anytime of the year, fall is an excellent treatment time. As with common buckthorn, a 20-25% Glyphosate mixed with water or 12.5% Triclopyr mixed with a bark penetrating oil applied to the cut stump is the most effective control method. *Note: non-native honeysuckle is very persistent, and will re-sprout readily if not treated with herbicide. Smaller plants can be hand pulled due to a shallow root system.
Japanese barberry (Berberis thunbergii)
Japanese barberry was introduced as an ornamental from Japan around 1875. It is a thorny shrub that commonly grows 2-3’ in height and is typically found along woodland edges, roadsides, fences, old fields, and open woods. Japanese barberry has small leaves found at each thorn axis and red, hanging, oblong berries can be seen fall through winter. A distinguishing characteristic of Japanese barberry is the bright yellow wood and inner bark found when stripping a branch. A foliar treatment of 2% Glyphosate or 2% Garlon 3A mixed with water should be applied to the leaves of mature plants and re-sprouts. If control is performed in a sensitive natural area, a cut-stump method of 12.5% Triclopyr mixed with bark oil should be applied to the cambium layer of the cut stump.