Weed of the Month: Bush honeysuckle—an ornamental gone wrong

Published: September 24, 2015

Bush honeysuckle, also referred to as Amur honeysuckle (Lonicera maackii), was introduced into the U.S. as an ornamental for city landscapes in 1897.  The plant was promoted for soil stabilization and reclamation programs in the 1960’s.  Bush honeysuckle is a relative to the native and non-invasive honeysuckles of the U.S.; however, its ability to easily establish and grow in many environments such as lake and stream banks, floodplains, meadows, prairies, and forests (Figure 1) warrants concern.  Bush honeysuckle is rapidly spreading through forests in the northern U.S.¹ where it is displacing native annuals and perennial herbs and disrupting species diversity¹.  This invasive plant can be found from the east coast to Texas, Kansas, Nebraska, and North Dakota and has been introduced in Oregon; it is listed as a noxious weed in Connecticut, Massachusetts, and Vermont². The plant’s invasive ability may in part be due to allelopathic effects on surrounding plants, a rapid growth rate relative to desirable plants, and the ability to tolerate moderate shade and outcompete neighboring plants for the available sunlight.  Recent work by researchers in Ohio has shown that bush honeysuckle can also outcompete neighboring plants for water with its fine root system. The scientists found that the majority of bush honeysuckle’s roots are located within the top 5 inches of the soil¹.

Bush honeysuckle seedlings emerge in the spring; the cotyledons are ovate to oblong and have an indentation at the apex. This deciduous shrub grows upright and can reach heights over 6 feet.  The plants’ stems and branches are usually hollow, which is a characteristic that can help distinguish bush honeysuckle from the native, non-invasive honeysuckles, which have solid stems. Leaves are attached opposite to each other along the branch and can grow up to 3 and 1/2 inches long and 1 and 1/2 inches wide.  Each leaf blade tapers to an elongated tip (Figure 2).  The upper leaf surface is usually dark green and has no to few hairs; the lower leaf surface is a lighter green and has hairs along the leaf veins. 

Unlike the native honeysuckles, which produce yellow flowers, bush honeysuckle produces white flowers from May into June. These flowers are fragrant and turn to a creamy yellow color as they age. Bush honeysuckle flowers occur in pairs at the junction of the stem where the leaves branch out.  Flowers are approximately ¾ to 1 inch long and have 2 lips (Figure 3).  The five petals of each flower are fused together to form the honeysuckle tube.  In early fall, bush honeysuckle plants begin producing distinct, bright red berries that are approximately ¼ inch in diameter and contain 2 to 3 seeds each (Figure 4).  Birds and white-tailed deer have been shown to eat the berries and aid in the spread of the weed³.  In mid to late fall, the plant’s leaves will turn yellow (Figure 5) and then drop off, leaving bare shrubs that can provide effective camouflage for deer during November. 

Identification of bush honeysuckle seedlings and hand pulling the young plants in early spring can be effective in preventing or minimizing infestations of the weedy shrub. Controlled burning in the spring can kill seedlings and the new growth of established plants. However, bush honeysuckle can readily resprout, therefore one burning will not control mature plants. Research indicates that mowing is only marginally effective at reducing infestations given the plant’s ability to sprout from the crowns following the cutting.

Two of the most effective chemical options for bush honeysuckle control are triclopyr (Remedy Ultra, Pasture Guard) and glyphosate (Roundup, Touchdown). University of Missouri research has shown that foliar applications of these herbicides are generally more effective than either cut-stump or basal bark applications. For foliar sprays, apply a 2 percent solution of the active ingredient in water with a nonionic surfactant in early spring or in the fall prior to the leaves changing color. It is important to note that glyphosate is a non-selective herbicide and will kill or injure non-target plants, such as legumes and grasses, which it contacts. Applications may be easiest in the fall, when surrounding non-target plants have already gone to dormancy and while the bush honeysuckle leaves are still green. For a cut-stump application, apply a 20 percent glyphosate solution with a sprayer or brush, thoroughly coating the freshly cut stump. Always check the herbicide label for instructions and confirmation of herbicide use rates.

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To read more about bush honeysuckle or check out other common Missouri weeds, visit our Web site: weedid.missouri.edu

For more information on the control of weeds in forages, pastures, and noncrop areas, order a copy of the latest version of IPM1031: http://extension.missouri.edu/p/ipm1031

To see a 2010 county-by-county map of bush honeysuckle presence in the state visit: https://plantsciencesweb.missouri.edu/deltaweeds/pdf/mdc/Bush_Honeysuckle.pdf

¹Pfeiffer SS and DL Gorchov (2015) The American Midland Naturalist 173(1): 38-46.

²USDA-NRCS Plants Database: plants.usda.gov

³Castellano SM and DL Gorchov (2013) Natural Areas Journal 33(1): 78-80.

⁴Smith K and A Smith (2010) Controlling Non-Native Invasive Plants in Ohio Forests: Bush Honeysuckle: http://ohioline.osu.edu/for-fact/pdf/0068.pdf