Invasive Plants Destructive to the Environment; Natives Are More Suitable Alternatives

With spring and a new gardening season coming in a few weeks, it is an ideal time to consider the invasive plants in our landscape and native plants that are suitable alternatives.

The Connecticut Invasive Plant Working Group defines an “invasive plant as a species non-native to the ecosystem under consideration, and whose introduction, whether accidental or intentional, causes or is likely to cause harm to the environment, economy or human health.”

Autumn olive (Elaeagnus umbellata) was introduced into North America from eastern Asia. With fragrant flowers, the ability to grow in adverse conditions, and fruit that is eaten by dozens of bird species, autumn olive has been promoted as an ornamental and wildlife plant. 

If so many birds love its fruit, what is the problem with autumn olive? With the potential for a mature plant to produce as many as 66,000 seeds annually, it can quickly become the dominant plant in an area, outcompeting native plants. It also has allelopathic properties. It releases growth-compounds from its roots and other plants that try to establish themselves absorb the chemicals and die. Few insects feed on autumn olive  giving it little value for spring migrating and nesting birds.

Autumn olive. Photo: nps.gov

Three other plants introduced into North America from Asia, Japanese barberry (Berberis thunbergii), winged euonymus (burning bush) (Euonymus alatus), and Japanese honeysuckle (Lonicera japonica), can also become dominant plants in the landscape. They are especially harmful in the forest understory where they shade out native plants and result in a monoculture. And again, they do not support the insects that birds need for their growing chicks. 

Japanese honeysuckle. Photo: hort.uconn.edu/plants

More suitable native plant alternatives for these non-native plants include several of the plants that are included in Menunkatuck’s Plant Sale for the Birds. Winterberry (Ilex verticillata), red chokeberry (Aronia arbutifolia), and highbush blueberry (Vaccinium corymbosum) all have berries that provide food for wildlife with the additional benefit of flowering in May, June, or July, attracting insects that nesting birds can feed their chicks. An alternative to Japanese honeysuckle is trumpet honeysuckle (Lonicera sempervirens), a native vine that is attractive to ruby-throated hummingbirds.

Trumpet honeysuckle. 

Photo (color adjusted): hort.uconn.edu/plants 

Karen Bussolini will discuss more ideas for Landscaping with Native Plants: Healing Our Home Turf at Menunkatuck’s March 13 program. 

(From the March 2013 Newsletter)

Japanese Barberry and Lyme Disease

An article in the New London Day describes a link between the invasive Japanese barberry and Lyme disease.

Jeffrey Ward, chief scientist at the Connecticut Agricultural Experiment Station's Department of Forestry and Agriculture, and experiment station scientist Scott Williams have been doing research on the relationship between Japanese barberry, ticks that carry Lyme disease and deer overpopulation.

A highly invasive plant that forms dense canopies in forests - particularly those with high deer populations that eat most every other plant - Japanese barberry also creates moist, cool shelters that harbor ticks that carry the Lyme disease bacteria, Ward's and Williams' research has shown. Hot, dry conditions suppress tick populations.

At 28 study areas, including a parcel along Lord's Cove in Old Lyme, the two have been studying various aspects of the triangular relationship between ticks, deer and barberry, and spreading their message to land conservation organizations about the best methods for ridding forests of barberry. Deer serve as hosts for adult ticks, while the barberry functions as a nursery for ticks in their juvenile stages.

Williams said tick abundance in barberry-infested areas is 67 percent higher than those where native plants are predominant. Also, the percentage of ticks that carry the Lyme bacteria is higher - 126 infected ticks per acre versus 10 per acre in barberry-free areas, Williams said, though the reason for that is as yet unclear. After barberry removal, Ward said, tick populations drop as much as 80 percent.

Go here for the full story.