Non-Native Invasive Species

Exotic bush honeysuckles

Lonicera sp.

Lonicera sp.

Exotic bush honeysuckle
Photo: Patrick Breen, Oregon State University, Bugwood.org

The exotic bush honeysuckles of our region - Morrow's honeysuckle, Tatarian honeysuckle, and Bell's honeysuckle (a hybrid of the two) - pose a huge threat to native forest biodiversity in the Northeast. First brought to North America from Japan and Russia as long ago as 1752, these species and their hybrid have taken over disturbed lands - including managed woodlots - from southern Canada to the mid-Atlantic and Midwestern states. They are particularly problematic in Vermont in the Taconic Mountains in Bennington and Rutland counties, and in the Champlain lowlands.

Exotic bush honeysuckles are larger and coarser than our native honeysuckles, and leaf-out weeks earlier and retain their leaves weeks longer than the native shrub species, so they are easily distinguished from the one or two natives present here.

Lonicera sp.

Exotic bush honeysuckle
Photo: Patrick Breen, Oregon State University, Bugwood.org

The non-natives, though, are hard to distinguish one from another. Morrow's honeysuckle flowers are white fading to yellow, and flowers, stems, and leaves are all slightly hairy. Tatarian honeysuckle flowers are white to pink, and plant parts are smooth. But the hybrid has characteristics of both parents, and all have red, or rarely yellow, berries.

It doesn't matter much, however, which non-native honeysuckle it is. All three are hugely aggressive, common along roadways and in hedgerows, along streambanks and railroad tracks. And they are together one of the most common elements in the understory in young forests throughout the western part of Bennington County, where they have already greatly reduced the number and coverage of native woodland species in our area - including tree seedlings in logged forests.

Lonicera sp.

Exotic bush honeysuckle
Photo: Leslie J. Merhoff, University of Connecticut, Bugwood.org

Land managers agree that where these plants are abundant they pose an overwhelming challenge. But where populations are smaller, control is possible.

We can cut or pull plants at least once a year for three to five years, until root reserves are used up. (Researchers caution against cutting in winter, which encourages vigorous re-sprouting.) Small shrubs can be pulled with a tool called a Weed Wrench™. Large shrubs require heavy equipment and chains. Or for those willing to use herbicides, glyphosate and triclopyr (brand names Roundup™ or Rodeo™, and Garlon™ respectively) can be safely and effectively brushed on cut stumps from late summer through early spring. The flush of seedlings that follows such cutting must be controlled too.

That flush of seedlings, and the plants' invasiveness generally, are results of prodigious seed production, and dispersal of seed by birds. And therein lies one nice thing I can say about this group: the plants were once popular in part because of their value for birds, and studies have found that they can be an important source of winter food for birds where few other shrubs survive or after native seed sources have been consumed.