Native and Invasive Plants
The problem of invasive plant species has become one of the top threats to natural areas. Just what exactly is an "invasive" species? It is a species of non-native plant that has the capability of degrading a natural ecosystem. Aggressive invasives compete for the light, water, nutrients and space available to native plants. Invasive plants also alter the moisture and chemistry of the soil. Some have been found to harbor plant pathogens, (such as leaf scorch), that can affect both wild and ornamental plants. The management of invasive species is expensive, causing great economic
losses and expenditures each year, measured in billions of dollars, for agriculture, forestry, range lands and roadways management. Native plants host native insects, which in turn feed birds, creating a healthy ecosystem.
Briar Bush's summer newsletter featured a warning about Butterfly Bush. See Rodale's article about this non-native species:
Increasingly, land managers are focusing their attention on getting the word out about this problem. Here are a few examples of some of our toughest invaders at Briar Bush. As you are making your plans for your spring garden, take a look around and see if you can help with this problem by rooting out any of these "Least Wanted" plants from your yard.
English ivy is an evergreen climbing vine that attaches to the bark of trees, brickwork and other surfaces by way of small root like structures. Leaves are dark green with white veins and are somewhat leathery. This hardy plant is a popular choice for ground cover in dry shady spots with poor soil, where it is difficult to get other plants to grow. However, once established it crowds out all other plants that might grow on the ground, and it climbs up trees and blocks the light from reaching the leaves. In this way, English ivy will eventually engulf a tree and choke off its growth, either killing the tree directly or weakening it enough to allow other forces to move in for the kill.
Fortunately there are many native and non-invasive alternatives for ground cover in dry shady areas. Examples include: wild ginger, Allegheny spurge, (scientific name Pachysandra procumbens, not to be confused with Japanese pachysandra which is another invasive species), and a pretty little plant called "green and gold" or "goldstar" that is becoming increasingly popular. Also ferns like Christmas and cinnamon fern will grow in these areas, and decorative grasses and sedges like wild oats, bottlebrush grass and Pennsylvania sedge. If it's vines you're looking for, then trumpet vine, Virginia creeper and native clematis, (scientific name Clematis virginiana, often called Virgin's bower) will fill the bill.
Japanese barberry is a familiar garden shrub, planted because its thorns make it unpalatable to many garden pests like rabbits and deer, its foliage turns a pretty red in the fall, and its bright red berries persist into winter to add color to the landscape. Unfortunately, because this plant's leaves aren't eaten by forest browsers, it has a competitive advantage and is often the only shrub left in the understory of a disturbed urban forest. Birds do eat the seeds however, and spread the plant far and wide in their droppings. Barberry alters the soil pH and nitrogen levels in forest soil, making it no longer suitable to the growth of native wildflowers.
If it's a pretty landscape shrub with red fall color and bright red berries you're looking for, there are plenty of alternatives. Some examples are blueberries (gorgeous fall color) or winterberry holly and Sargent crab (gorgeous red berries) and cotoneaster, or inkberry holly, a native shrub with small persistent leathery leaves.
Norway maple is a fast growing shade tree, and therefore popular as an ornamental. It can be differentiated from other maples by the milky white sap exuded when a leaf or twig is pulled from the tree, or by its grey, tight bark with thin closely-packed furrows. Norway maples do not put on much of an autumn show, the leaves turn dull yellow and don't fall off until November. The fast growth of this tree is one reason it is so invasive, its shallow roots quickly absorb water and nutrients from the soil, making it inhospitable for almost anything growing under it, including a lawn! But this fast growth comes at a price and the tree is not long lived, often succumbing to heart rot. For this reason, you might find large branches from Norway maple falling on the yard, street or roof during strong windstorms.
If you're fond of maples and want a reasonably fast growing shade tree, look for red maples, scientific name Acer rubrum. For other fast shade options, there are many beautiful natives to choose from, including basswood, tulip tree and pin oak. American ash was once a favored choice, but it too is fading due to an invasive bug called the emerald ash borer. Thornless honey locust is available and you will often see that tree planted in adverse conditions. But if you really want to do future generations a favor, plant and nurture a mighty red or white oak!
Reference the information for this article came from the Web site of the National Park's Plant Conservation Alliance. Check it out for further information on "America's Least Wanted" Weeds! For information about attracting wildlife with native plants, try the state's native plant index here: Plant Native Plants!