DEBRA BURROWS/FOR THE EXPRESS Invasive bush honeysuckle begins to show green growth before native vegetation in this field in Clinton County.

After a long, gray winter, I’m usually very happy to see signs of green returning to central Pennsylvania. As an enthusiastic gardener, I tend to think all green is good. Unfortunately, that’s not the case. In many areas of Clinton County, the first signs of green I observed this spring were from invasive shrubs commonly referred to as bush honeysuckle. These honeysuckles begin to push out green leaves weeks before our native Pennsylvania shrubs and trees. At first, they seem a welcome sight, but don’t be deceived. Bush honeysuckle is a menace.

The term “bush honeysuckle” includes several species of honeysuckle (Lonicera, spp.) that were imported from other continents for use in erosion control, wildlife food and habitat and as ornamental landscape shrubs. Research has shown that rather than helping, these bush honeysuckles did just the opposite and are now ranked among the worst invasive shrubs in Pennsylvania.

Bush honeysuckles are vigorous growers that spread rapidly. They are large shrubs, generally between six and 12 feet tall and wide, although given the right conditions, they can become even larger. They have arching branches with thick canopies of leaves that create dense shade, making it difficult for anything else to grow underneath them. They have shallow root systems and prefer sun but will tolerate shade. In spring they produce fragrant flowers in shades of white, yellow and pale pink which are followed by abundant red berries. There is some evidence that bush honeysuckles release chemicals into the soil to inhibit the growth of other nearby species, including trees. Bush honeysuckle shrubs can form colonies which take over entire areas and decimate native vegetation.

The loss of native vegetation is a serious concern because insects, birds and mammals depend on native plants for both food and habitat. The berries of bush honeysuckle, although plentiful, have much lower nutritional value than the berries produced by native plants such as blueberry, blackberry and wild grape. Bush honeysuckle berries are high in carbohydrates, but not in fat and nutrients which are essential, especially for migrating birds. When bush honeysuckle outcompetes native plants, the area’s food resources become diminished and wildlife suffers or is forced to relocate.

Bush honeysuckle is inferior to native shrubs in providing habitat as well. Nests built in bush honeysuckle are vulnerable because its stems lack thorns which deter predators. Its arching branches are easy to climb and do not provide safe nesting sites.

By decreasing the number and variety of native plants, bush honeysuckle deprives pollinators of the specific plants they need for reproduction. Studies have shown that certain insects have very specific plants which they rely on to provide sites for egg laying and food for the caterpillars which hatch from those eggs. An oft-cited case is the monarch butterfly which can only utilize milkweed (Asclepias, spp.) as a host plant for its eggs. Simply put, no milkweed means no monarchs. Similar dependent relationships are exhibited by other insects and their host plants. By crowding out native plants, bush honeysuckle removes the very plants that insects need to reproduce. When insect populations are decreased, bird populations decrease as well because birds depend upon insects for food for their young.

Insects, birds and other wildlife are part of the web of life of all living things. According to the USDA, “Three-fourths of the world’s flowering plants and about 35 percent of the world’s food crops depend on animal pollinators to reproduce. That’s one out of every three bites of food you eat. More than 3,500 species of native bees help increase crop yields.” (www.usda.gov/about-usda/general-information/initiatives-and-highlighted-programs/peoples-garden/importance-pollinators) Clearly, making sure pollinating insects have the food and habitat they need is in our own best interest.

As I traveled around Clinton County this spring, I realized how widespread the problem of bush honeysuckle has become. In late March and early April before native plants had begun to “green up,” I saw extensive green growth of bush honeysuckle in hedgerows, along roads, on the edges of forests, in vacant lots and overgrown fields, along State Route 220 and Interstate 80 and nearly everywhere I looked.

Bush honeysuckle is a problem we can manage locally and there are several options for controlling it. Penn State Extension has information and photographs to assist property owners with both identification and control of bush honeysuckle at extension.psu.edu/shrub-honeysuckles. For bush honeysuckle on public property, contact the appropriate municipality, county or state agency that is responsible for the site where it is growing.

Additional information on bush honeysuckle is available from Ohio State University Extension at ohioline.osu.edu/factsheet/F-68 and from Purdue University at extension.purdue.edu/news/county/marion/2021/08/IPSAWG-AsianBushHoneysuckle.pdf .

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Debra C. Burrows, PhD, is a retired Penn State Extension Educator and a certified Master Gardener. She can be reached at dcb3@psu.edu.