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greenliving The Challenge of Managing

Invasive Species

by Megy Karydes I

nvasive species are plants and crit- ters that are living where they don’t belong, crowding out those that do. Sometimes the invaders grow faster or taller and block the sunlight that native plants need to survive. Many home gar- deners unknowingly introduce invasive plants into their backyards when they plant nursery-grown or wild plants into their gardens. Ecologist Cathy McG- lynn, coordinator for the Northeast Il- linois Invasive Plant Partnership (NIIPP), defines as invasive any organism that is expanding the area it inhabits outside of its historically documented range. “What makes invasive species

invasive is that they have no natural predators or checks in the habitats where they are introduced,” she says. In addition, several invasive species, like buckthorn and honeysuckle, keep green leaves much longer into the fall than native plants; this allows them to store additional food reserves for overwinter- ing and gain a competitive advantage over native species.” To halt the spread of invasive species, McGlynn recommends two approaches to home gardening: make smart choices for garden and landscape areas by purchasing native plants and root out invasive plants that are just starting to be introduced. “The idea is to take advantage of the fact that once detected, we can easily eradicate

40 Chicago North & North Shore

populations when they are small and isolated,” says McGlynn. It’s important to note that a number of these species were once just ornamental plants that escaped from gardens and landscaped areas. “Plants ‘escape’ via root expan- sion, plant parts transported by water, wind, or through animal and seed dispersal,” she explains. Gardeners may wonder why garden centers are able to sell invasive species. “The key here is that many of the species weren’t invasive to begin with,” notes McGlynn. “Folks just

Bradford Pear

didn’t know. Many invasive plants have lag times. They remain contained and ‘well-behaved’ for long periods of time until conditions change and suddenly they are able to rapidly reproduce and spread.”

McGlynn also recognizes that

beauty and novelty drive the nursery market, which works hard to keep up with consumer demand. “This results in the green [commercial nursery] industry searching farther and farther from the Midwest for new and excit- ing plants that gardeners joyfully bring home and plant in their gardens,” says McGlynn. “Looks like it might be time for a change in perception about what is beautiful and desirable in gardens!” Many of the plants that we know are becoming invasive continue to be sold because there are no laws to pro- hibit their sale, and gardeners that have come to love particular plants are often very unwilling to give them up, accord- ing to McGlynn. “In addition, green industry folks take many years to build up stocks of particularly popular plants, and they can’t just stop selling them all at once,” she says. The NIIPP lists these relatively common garden plants as invasive and to be avoided: burning bush, Japanese barberry, purple loosestrife, Japanese knotweed, porcelain vine, butterfly bush and Callery pear (Bradford pear).

For a complete list of invasive species and target species, visit

Megy Karydes writes regularly on sustainability and after 11 years, is still ripping out mint that the previous own- ers of her home had planted. Find her at

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