‘Keep it native, not invasive’

Ingrid Mroz

Wiley’s Corner resident Ingrid Mroz heads up the St. George Conservation Commission’s new Invasive Plant Initiative, but she seems a little apologetic about it. “I’m a gardener, but not a master gardener. And with respect to invasive plants I am a novice at best,” she admits, despite the thick stack of notes and printouts about the impact of “alien” plants that sits on the coffee table in front of her, ready for easy reference. Now retired from the faculty of Dartmouth-Hitchcock Medical Center where she specialized in adult critical care, Mroz knows how to research a topic in depth. But her understanding of what’s at stake in the battle against these problem plant species comes as much from personal experience as from the research she’s been conducting on the topic since heading up the commission’s invasives initiative.

“I didn’t even know what an invasive plant was, truly—it wasn’t anywhere on my radar until we moved to St. George and bought this property seven years ago. Once here, we began to see how certain plants were taking over our property in ways that we weren’t wanting because we had other things we wanted to do with the grounds.”

One of the first of those “other things” was to rescue and expand a raspberry bed inherited from a previous owner. “My husband Bill and I wanted to have a very nice berry patch and there was a large rectangular bed that had fall raspberries in it that we decided to develop. But in amongst all of that were Multiflora Rose, Oriental Bittersweet and Himalayan Balsam. It took us one solid month to clean that rectangle out.” Mroz and her husband then also planted early season raspberries and native blueberry bushes in the bed. “The only thing we’re still battling is the bittersweet,” Mroz now says with satisfaction.

Surveying the rest of their six-acre property, the Mroz’ were also disappointed by how much Himalayan Balsam there was. Eager to begin “farming” in earnest, they began beating the balsam back to clear a space for vegetable beds. Eventually they enlisted the aid of a Kubota tractor and a bush hog to establish a vast kitchen garden that encompasses 3,000 square feet of ground and provides most all of the vegetables the couple consumes each year.

Growing vegetables at this scale made the couple even more conscious of their need for pollinators. Bill built pollinator boxes, but they also began assessing what invasive plants were doing to limit the diversity of vegetation on their property and, thereby, the diversity of insects. A love of birds, too, sharpened their awareness.

“I’m a birder,” says Mroz, “and a lot of these invasive bushes are not good for birds, they are not so nutritious for them as native plants tend to be. As part of the planting plan we have for this property, I think especially about the plants the birds and pollinators are interested in.” This will involve, for example, choosing native plants for new foundation plantings around their home now that exterior renovations have been completed. Previously those plantings had been of invasive species—plants that previous owners found desirable largely for aesthetic reasons. That’s the irony, Mroz says, about the invasives problem.

“A lot of the invasive species we have were planted,” she explains. “The Knox/Lincoln Soil and Water Conservation District actually sold some of these plants. And it was only in 2018 that the State of Maine identified 33 invasive plants that nurseries could no longer legally sell because these plants have been spreading voraciously across the land and overtaking native plants that are far more beneficial for birds and animals and bees and so on.” So expecting property owners to suddenly get rid of these plants is unrealistic, Mroz notes, although incrementally progress can be made. “At our property, there are some invasives that we’ll be able to get rid of completely and others that we won’t be able to eradicate completely, but we may be able to limit their spread.”

More difficult might be convincing people who love the look of a mown lawn that these areas are, ecologically speaking, negatives.

Providing educational materials that can support St. George property owners who want to make their own environments as ecologically hospitable to insects and wildlife as possible is one aspect of her invasives work for the Conservation Commission, but at this point Mroz and her colleagues are giving even greater attention to St. George’s public lands. Apart from the new Meadowbrook preserve and High Island, which have no invasives, most of the rest of these lands have thriving populations of invasive plants. Last year the commission co-sponsored with the Georges River Land Trust an “Invasives Walk and Talk” on the Fort Point Trail. This year there will be a program at Blueberry Cove Camp on June 8, “Invasive Plants of St. George: Hands-on Management and Methods,” that will involve identifying invasives on the property and demonstrations of how best to remove some of them.

Meanwhile, St. George students, with the assistance of faculty, Alison England and Amy Palmer, have been studying invasive plants and their impact, identifying and mapping invasive plants located on school property and along Ripley Creek. The students also brainstormed slogans to raise public consciousness about the threat invasives pose to ecological health. The commission chose to adopt one of these, “Keep it native, not invasive,” in some of its future publicity materials. —JW

PHOTO: Julie Wortman

On the importance of encouraging insect life—and why native plants are key

University of Delaware professor Doug Tallamy, author of Bringing Nature Home: How Native Plants Sustain Wildlife in our Gardens (Timber Press), points out that insect populations have declined 45 percent globally since 1974. “A world without insects,” his website declares, “is a world without humans!” In other words, if you remove insects from an ecosystem, the ecosystem will collapse because so many other creatures, directly or indirectly, depend on insects for food. And insects depend on plants native to where they live.

To illustrate, Tallamy notes that about 96 percent of all terrestrial birds rear their young on insects. And about 90 percent of all insects that eat plants require native plants to complete their development. That is because plants protect their leaves from being eaten by random creatures with toxic chemicals. Insects can survive after eating those chemicals only after they have evolved physiological mechanisms for detoxifying them. This requires a long evolutionary history between insects and their host plants. Native insects only have such histories with native plants. They have not been exposed to plants that evolved in Europe or Asia—what we call aliens—long enough to be able to use them as host plants successfully.

The conclusion? That every time we plant an alien plant, we are reducing the local insect population and thus depriving the birds and wildlife of the food they need to survive and reproduce. Tallamy and others cite studies that have shown that areas overrun with alien plants produce 35 times less caterpillar biomass, the most popular insect food with birds. Alien plants used in the traditional ornamental trade (think many nurseries) support 29 times fewer species of caterpillars than native ornamental plants. —JW

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2 thoughts on “‘Keep it native, not invasive’

  1. Steve Cartwright

    Helpful article, and hope there’s a good turnout for the Blueberry Cove program in June. When I first saw the headline, I thought, “Uh oh, I hope this doesn’t mean people.” Although we are in some sense an invasive species.

  2. Barba

    Ingrid and Bill Mrz are neighbors but I only know them a little from delivering mail in the past. Love their little farmstand which displayed some birdhouses recently. Really enjoying reading your article about her research on invasives. Thank you all


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