Exploring The Last Green Valley: Invaders in our Backyards and Woods

Over the past few years, I have used this column to highlight concerns with invasive plant species having a severe, negative impact on the natural resources of our region. It seems wherever I go in The Last Green Valley, I am confronted with one or more invasive plants strangling our native species out of growing space in our open lands, forests and waterways.

The spread of invasive plants is such a statewide concern that in 2003 the Connecticut General Assembly passed Public Act No. 03-136, An Act Concerning Invasive Plants. This act established an Invasive Plants Council to help educate the public and merchants and consumers of invasive aquatic and land-based plants to the problems associated with invasive plants.

Public Act No. 03-136 was followed in 2004 with Public Act No. 04-203, An Act Concerning Fines for Banned Invasive Plants. The key language of this act is “no person shall import, move, sell, purchase, transplant, cultivate or distribute any of the following invasive plants.” A long list of invasive plants follows.

One of the more useful resources for understanding our region’s invasive plants is the Connecticut Invasive Plant Working Group (CIPWG) located at the University of Connecticut. They have a very helpful website and it is the first resource I use in learning more about an invasive plant. Check it out at http://cipwg.uconn.edu.

CIPWG defines invasive plants as “non-native plants that are disruptive in a way that causes environmental or economic harm, or harm to human health.” In minimally-managed areas, invasive plants crowd out native plants. The presence of invasive plants alters the way plants, animals, soil, and water interact within native ecosystems, often causing harm to other species in addition to the plants that have been crowded out. Invasive plants have many things in common, including:

– The ability to establish new plants and grow rapidly under a wide variety of site conditions.

– A high reproductive rate.

– The ability to disperse wide distances, often by the spreading of vegetative fragments as well as seeds.

– The lack of natural controls on growth and reproduction that would be found where the invader is native.

Here are descriptions from the CIPWG website of several invasive woody stem plants I frequently find when walking the woods and open lands of the national heritage corridor. I have battled to eradicate many of them from my property in Putnam, as well as property my family owns in Fitzwilliam, New Hampshire.

Japanese barberry

Japanese barberry is a multi-branched dense shrub that can grow to 8 feet in height. Shiny green to burgundy leaves alternate along its thorny stems. Solitary yellow flowers bloom from March to April, and the fruit is a round or elliptical red berry. Japanese barberry is a popular landscape shrub that has escaped into many natural areas and can grow in dense thickets in the understory of woods and forests. It is a prolific seed producer, and numerous birds eat and disperse the seeds. Japanese barberry has been in the news recently as some researchers believe it plays a role in the increase of tick-borne diseases. CIPWG has collected several informational links about the issue on its website.

Multiflora rose

Multiflora rose is a large, dense shrub that has escaped from ornamental and conservation plantings to become a serious invasive plant problem across the eastern half of the U.S. It invades natural areas, pastures and light gaps in forests. Multiflora rose produces abundant small white flowers in the spring. Birds and mammals consume the red fruits, called hips, and may disperse them long distances. The majority of plants develop from seeds in the soil, which may remain viable for 10 to 20 years. It may also spread when tips of arching branches touch the ground and develop roots (called layering), and from plants that emerge from shallow roots. Multiflora rose spreads quickly and may grow 1 to 2 feet per week to form impenetrable thickets of thorny stems.

Common European buckthorn and smooth glossy buckthorn

Common (European) buckthorn and smooth (glossy) buckthorn are exotic shrubs that readily invade natural areas. They have long growing seasons, rapid growth rates, and re-sprout vigorously following removal of above-ground tissues. Common buckthorn is typically found in woodlands and open fields, while glossy buckthorn most commonly invades wetland communities, but can also be found in upland sites, such as roadsides and old fields. Plants of both species reach seed bearing age quickly. Common buckthorn blooms May through June during leaf expansion. It produces black fruits that ripen in August through September. Glossy buckthorn blooms after leaf expansion in late May through September, and can blossom on the current season’s growth. Its fruits are initially red and turn black as they ripen in July through August. Fruits of both species are eaten by birds that can disperse them over great distances

Autumn olive

Introduced to the U.S. from Asia, autumn olive is a fast-growing woody shrub or tree that can grow to 20 feet. It has simple, alternate oval leaves with silvery undersides. The fragrant small white flowers reach peak bloom around mid-May. The fleshy fruits are brown at first but gradually turn red with silvery dots. Autumn olive has been planted extensively for wildlife habitat, strip mine re-vegetation and erosion control. It has been marketed widely as an ornamental. It produces abundant fruits that are consumed and spread by birds and small mammals. Autumn olive grows well in disturbed areas, open fields, forest margins, roadsides and clearings. It is intolerant of shade and will not invade dense forests. However, because its fruits are eaten by a variety of wildlife, its seeds may be distributed into forest openings or open woodlands.

Winged euonymus (burning bush)

Winged euonymus is a deciduous shrub, up to 20 feet in height, which invades forests throughout the eastern United States. Occasionally, four corky ridges appear along the length of young stems. The opposite, dark green leaves are two-inches long, smooth, rounded and taper at the tips. The leaves turn a bright crimson to purplish color in the fall. The flowers are inconspicuous, greenish yellow and have four petals. Flowers develop in the spring and lay flat against the leaves. Fruit are reddish capsules that split to reveal orange fleshy seeds. Winged burning bush can invade a variety of disturbed habitats, including forest edges, old fields and roadsides. Birds readily disperse the seeds, allowing for many long dispersal events. Once established, it can form dense thickets that displace native vegetation. Winged burning bush is native to northeastern Asia and was first introduced into North America in the 1860s for ornamental purposes. It currently continues to be sold and planted as an ornamental or roadside hedge.

These invasive woody stem plants are just as few of the many listed as invasive species in our region. Some have thankfully been banned from sale, but some, surprisingly, are still available for purchase.

To appreciate our region’s beautiful natural habitats is to also understand the things that threaten it. I hope you’ll join me and others in learning about the impact invasive species have on our fields, forests and waterways. Let us work together to help control their negative impacts on our natural world.

Bill Reid is chief ranger of The Last Green Valley National Heritage Corridor. He has lived in the region for more than 30 years and can be reached at bill@tlgv.org