More Bad News About Non-native Plants from the EEC

Our thanks to Ann Farnham of the Ewing Environmental Commission for sharing this article with us about our continued use of non-native plants in the landscape.

We continue to hammer away on the disadvantages of using non-native plants. Remember, a good definition of a native plant is one that existed in any specific region before the European settlement in this country. Ewing is in the Mid-Atlantic region and our natives are well adapted to our particular soils, precipitation, temperatures, elevations and exposures. Our native wildlife – insects, mammals, birds, reptiles – developed along with them.

Many people believe that if a plant is sold at a local nursery or garden center that it is all right to use. Unfortunately, that is not correct. Because we have no laws or ordinances that prohibit the sale of introduced or invasive plants (some states do), they are widely available. What we can do at this point is to be informed and avoid buying them.

What are some of the popular, non-native plants sold in local nurseries and garden centers?

In March, 2016 we wrote about Bradford Callery Pear, (Pyrus calleryana); In June, 2016 it was Acer platanoides, Norway Maple; in July, 2016, we wrote about Burning Bush, (Euonymus alatus); and in August, 2016, Winter Creeper, (Euonymus fortunei).  Unfortunately, these are all available at local nurseries and garden centers. A few more garden center boarders – invasives and aggressors – are listed below; most, having few natural predators, form un-challenged thickets at the expense of our native plants.

  • Butterfly Bush (Buddleia davidii): This vigorous, nectar-producing butterfly attractor is an attractive shrub with fragrant, colored flower spikes, It self-seeds prolifically, however, and before long your planting bed will be overcome with a Buddleia thicket which crowds out everything else. It is classified as noxious weed in Oregon and Washington.
  • English Ivy (Hedera helix): This popular and sometimes very lovely vine easily goes astray, spreading throughout woody areas and gardens, choking out other vegetation. English ivy kills trees and shrubs by smothering them.
  • Heavenly Bamboo (Nandina domestica): This is not a bamboo, in spite of its popular common name. All parts of the plant are toxic, especially to Cedar Waxwings, cats and grazing animals, resulting in many deaths. Heavenly Bamboo crowds out other plants with prolific seeds and underground stems.
  • Japanese Barberry (Berberis thunbergii) : This shrub is banned in Wisconsin and Massachusetts. It displaces native plants with prolific, bird-dispersed seeds, and harbors ticks (due to the high humidity in its dense foliage) mice, and, as a result, lyme disease.
  • Japanese Spirea (Spiraea japonica): this plant harbors many insects and diseases but still outcompetes and replaces native plants. Its seeds, dispersed by birds, form dense thickets which are very tolerant to many conditions. It impedes the germination of native seeds.
  • Japanese Wisteria (Wisteria floribunda): This very adaptable vine shades out other plants and girdles trees and shrubs as it climbs, cutting off nutrients by choking the trunks and producing dense shade.
  • Maiden Grass/Chinese Silver Grass Miscanthus sinensis: More than 50 ornamental varieties of this grass are sold in the United States. The wind-dispersed, viable seed forms thickets which are very adaptable to many conditions, choking out native plants. This is a very popular ornamental grass which is popular to use in a lot of landscaping.
  • Periwinkle Vinca minor: ( not V. major).This groundcover forms dense, extensive mats, choking out other plants. It harbors blights and is allelopathic, meaning that its chemical compounds inhibit the growth of nearby plants.               
  • Privet (Ligustrum sp):  This popular hedge plant is toxic to pets and mildly toxic to humans. Thousands of fruits outcompete and replace natives. The seeds, dispersed by birds, form  very dense thickets. Compounds in the leaves protect the plant from feeding insects, so it is “trouble free” for the hedge-growing home owner.

For more important information about non-native plants, read Plant Invaders of Mid Atlantic Natural Areas by Swearingen, Reshetiloff, Slattery, and Zwicker

Go to www.MAIPC, the Mid Atlantic Invasive Plant Council for additional plant lists.

Native plant alternatives to exotics can be found in the Brooklyn Botanical Garden’s Native Alternatives to Invasive Plants. In addition, be sure to visit the web sites:

  • The Native Plant Society of New Jersey for their
    • Tree recommendations for planting (both large and small)
    • Wild and Native Plants of NJ
    • Trees and Tall Shrubs by County
    • Invasive Species list
    • Wildflowers and Garden Conditions
    • link to the USDA database and
    • Plants by county.

Norway Maple – EEC Plant of the Month (Not!)

by Ann Farnham, LLA

Norway maple, Acer platanoides

No! Don’t plant this!

This maple tree is seen almost everywhere in the United States north of Hardiness Zone 7 and west to Minnesota. Native to Europe, it has thrived in the U.S.A. since it was introduced in the 18th century to Philadelphia by John Bartram, an early American botanist and horticulturist.

Acer platanoides adapts to extremes in soil (acid or alkaline, clay, sand), compaction, hot and dry weather, air pollution, and either full sun to part shade. As a result, its toughness has contributed to over-use as a street tree (especially after the Elm tree die-out), lawn specimen, and park tree. It has become invasive, crowding out native plants in our woodlands and forests because of its heavy seed crop and high germination rate, and site adaptability. Pests and diseases (Powdery mildew, Verticillium wilt, Anthracnose, Leaf scorch,) have not diminished its spread but the recent arrival of the Asian long-horned beetle may change that for the Norway maple as well as for all the native maples.

Why not?…

Why has the Norway maple fallen out of favor?

  1. It crowds out our native plants, about which we have become more appreciative and knowledgeable.
  2. It is very shallow-rooted, starving other plants of moisture and sunlight, so nothing can grow under its wide canopy (especially lawn grass and most ground covers); the roots also heave sidewalks and streets.
  3. It is fast growing and thereby brittle, causing extensive damage from breakage. Norway maple has been banned in New Hampshire, Maine, and New York.

This Maple is easily confused with our native Sugar Maple, Acer saccharum. They both have opposite, simple, 3 to 5 lobed, dark green, pointed leaves, but the Norway maple leaves are slightly larger, 4 to 7” across as opposed to the 3 to 6” Sugar Maple leaves. The Norway maple has a milky sap which can be extracted from its petioles (the leaf stalk) whereas the Sugar Maple sap is clear. The seeds in both species, samaras, are flattened, two-winged, and differ considerably as can be seen in the photographs.

Norway maple will occasionally reach 90’ in height although 40-50’ high is the average, with a spread 2/3 or equal to the height. It casts very deep shade. The fall foliage is usually yellow and the tree holds its leaves longer than other maples do. The wood is yellowish-white to pale red, and has been used for furniture making although the wood is reportedly not durable.

There are dozens of varieties of Norway maple which include a range of growth habits and leaf color, such as that of ‘Crimson King’ and ‘Dissectum’, which will doubtless continue to make this tree popular. Work is ongoing to develop sterile varieties.

To learn more about invasive plants, go to nps.gov/plants/alien and www.maipic.org

The Ewing Environmental Commission welcomes suggestions for the Plant of the Month from all Ewing residents.