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The Challenge of Managing Invasive Species

Mar 26, 2013 ● By Megy Karydes

Invasive species are plants and critters 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 gardeners unknowingly introduce invasive plants into their backyards when they plant nursery-grown or wild plants into their gardens. Ecologist Cathy McGlynn, coordinator for the Northeast Illinois 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 overwintering 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 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 expansion, 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 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]

Bradford Pear
Bradford Pear
industry searching farther and farther from the Midwest for new and exciting 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 prohibit their sale, and gardeners that have come to love particular plants are often very unwilling to give them up, according 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 owners of her home had planted. Find her at


May marks the Fourth Annual Illinois Invasive Species Awareness Month

(ISAM), dedicated to increasing public awareness about invasive species and providing solutions for dealing with this issue. Cathy McGlynn, coordinator for the Northeast Illinois Invasive Plant Partnership, says, “People need to care about invasive species for many reasons. Some species pose serious health risks to animals and humans, such as the giant hogweed, which produces a phytophototoxic sap that causes severe burns when affected skin is exposed to sunlight; and leafy spurge is toxic to cattle.”

Invasive species can decrease native biodiversity, such as when a native plant species that a particular butterfly depends on is outshaded by an invasive plant, so the butterfly has to look elsewhere for a place to oviposit its eggs and get its larvae fed, as well as find nectar for itself.

Some species affect entire ecosystems and nutrient cycling, such as buckthorn, which is is associated with higher erosion rates due to rapid leaf litter decomposition and prohibiting

Japanese Barberry
Japanese Barberry
growth of native plants in its vicinity.

Other species decrease or prohibit recreational use of certain areas. Anglers, boaters and kayakers don’t want to deal with the large, dense tangles of vegetation that Eurasian watermilfoil produces in regional lakes and ponds.

Illinois spends millions of dollars to control and eradicate invasive species every year in natural and agricultural areas, and people can become involved in ISAM in many ways.

• Get informed and learn to recognize and report invasive species that are found in the region.

• Make smart choices for garden and landscape areas by purchasing native plants and replacing invasive plants.

• Remove seeds and soil from tires, shoes, shoelaces, clothing and pets when entering and leaving natural areas.

• Clean any visible aquatic animals and plants from equipment or boats; drain bait buckets and bilge water; and dry aquatic equipment and vehicles for several days between uses.

• Volunteer to join a workday with volunteer stewards to help control invasive plants at a favorite natural area, meet like-minded people and enjoy some time outdoors.

For a list of invasive species and target species, visit