Hostile takeover

  • A stretch of tangled, mostly invasive plants has taken over the Merrimack River riverbank by Fort Eddy Plaza seen on Thursday, January 14, 2020. GEOFF FORESTER

  • A stretch of tangled, mostly invasive plants has taken over the Merrimack River riverbank by Fort Eddy Plaza seen on Thursday, January 14, 2020. GEOFF FORESTER

  • A stretch of tangled, mostly invasive plants has taken over the Merrimack River riverbank by Fort Eddy Plaza seen in 2020. GEOFF FORESTER / Monitor staff

  • A stretch of tangled, mostly invasive plants has taken over the Merrimack River riverbank by Fort Eddy Plaza seen on Thursday, January 14, 2020. GEOFF FORESTER

  • A stretch of tangled, mostly invasive plants has taken over the Merrimack River riverbank by Fort Eddy Plaza seen on Thursday, January 14, 2020. GEOFF FORESTER

For the Monitor
Published: 2/17/2021 4:17:31 PM

On Jan. 19, David Brooks reported on a plan to remove some invasive plants that have taken over the banks of the Merrimack River near Fort Eddy Plaza in Concord. Whether you look from the plaza side or the river side, it’s clear that the impenetrable jungle is in need of management.

Yet a few days after the article was published, a reader responded, complaining that this removal of vegetation would destroy wildlife habitat. I’d like to help her and others understand the difference between viable habitat and non-native tangle.

The offensive plants along the river include Oriental bittersweet, Japanese knotweed, European barberry and Japanese honeysuckle. The names of these plants indicate that they originate from other places. But that alone is not the problem. Many imported plants have become harmoniously naturalized in our landscape or are part of our vast agricultural menu. There’s a significant difference between non-native and exotic invasive plants.

Invasive species have several things in common which make them problematic. They are prolific seed producers and can reproduce profusely. With the help of birds, wind or water their seeds are transported, easily colonizing new areas. New leaves often emerge earlier than those of native plants and may stay longer into the fall, thereby creating a longer growing season and allowing for rapid growth. Unlike some of the native plants that have specific soil, light and water requirements, invasives are generalists, able to survive in a wide variety of conditions. One of the biggest issues is that they have not evolved along with native predators and so their surging growth is not kept in check.

With aggressive and unchecked growth, these plants easily outcompete or attack the native plants. Stately silver maples, adapted for being flooded each spring, and stabilizing the river banks are strangled by bittersweet vines that climb into the top branches, weighing them down to the point of collapse.

Native grasses and forbs are no match for the bamboo-like Japanese knotweed that grows with such profusion that no other plants can take root between or around their stems. This monoculture is a wasteland for small mammals, birds and insects compared with the richness of a native swath.

It may seem that these dense infestations of plants provide good shelter for wildlife, but shelter is only one necessary component of habitat. In order for there to be a diversity of wildlife, they must have a diversity of plant life providing various types of shelter and food.

Native shrubs are easily crowded out when barberry, autumn olive, multi-flora rose, non-native honeysuckles, burning bush or other rapid colonizers invade an area. While some of these invasives were intentionally planted years ago for the benefit of wildlife, the consequence of reducing the diversity of food sources was not known or anticipated, until it was too late.

In some areas it may seem that it is too late to control a thick jungle of invasive plants. Merely cutting down the plants only stimulates their growth. Pulling roots is easier said than done, and usually creates disturbed soil, an ideal platform for seeds of the invasive plants to take hold. Smothering the plants can work but is not practical in every situation and takes years to be thoroughly affective. Chemical herbicides are often used as the last resort but most potent weapon. All of these options are costly in labor and/or money. The economic impact of invasive species is significant in their destruction of desired species but also the cost of their management.

It is far better to minimize the introduction and spread of invasive plants in the first place. You may have some on your property. If so, consider removing them and replacing them with something native. Even a small patch or single plant can lead to an invasion as the seeds spread and colonize new regions beyond your sight. By eliminating your burning bush or autumn olive early, you’ll save yourself and your neighborhood from an invasion that could destroy the biodiversity of the local habitat.

The N.H. Department of Agriculture, Markets and Food has information about introduced plants that are a problem in our state agriculture.nh.gov/divisions/plant-industry/invasive-plants.htm. UNH Cooperative Extension provides resources and workshops on how to manage invasives at extension.unh.edu/search/google/Invasive%20plant%20management. With further investigation, you can uncover the twisted story behind a tangle of branches.




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