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

autumn-olive-nps

Autumn olive. Photo: nps.gov

When spring and a new gardening season comes 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.

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

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

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.

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.

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

Trumpet honeysuckle. Photo (color adjusted): 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.