NON-NATIVE INVASIVE PLANTS: What Are They And Why Are They of Concern? Non-Native Invasive Species (plants, animals, aquatic creatures and microbes): Were introduced into environments where they did not evolve Have no natural controls on growth, thus they can spread unchecked in their new environment Cost $138 billion annually (that number increases by a billion dollars each year) Removal and control cost $500,000,000 annually Are the greatest threat to biodiversity after habitat destruction Non-native Invasive Plants Invade grain fields, destroying or reducing crops and grazing pasture, costing billions of dollars annually Replace native trees causing losses in timber production Take the place of native plants by usurping their place in the landscape Can choke or smother native plants Can produce toxins that prohibit growth of native plants Replace native food sources used by birds and wildlife and reduce or eliminate host plants for native insects.
When Considering the Use of a Non-Native Plant in Your Landscape, Ask These Questions: Does it naturalize or self-sow? (If so, it may escape cultivation, invading woodlands and fields.) Does it provide food for wildlife? (The seeds of fruits eaten by birds and mammals can be dispersed outside your control.) Is it a rapidly spreading ground cover? (You may not be able to control its growth in natural areas.) Is it low maintenance: hardy, drought-tolerant, can withstand being wet, shade-tolerant, pest free? (This means it has no natural controls.) Can it kill or suppress the growth of surrounding plants by shading them, producing a chemical toxin or outgrowing them, depriving them of nutrients and water? (If so, it will out compete native plants and they will disappear from the landscape.) What You Can Do. Do Not Plant Them! If They Are Growing in Your Yard, Control by Deadheading, Knocking Off Fruit, or Pruning Remove Them from the Landscape Native Plants: Are better Adapted to Local Soil and Climate When Established, Require Less Water and Fertilizer Are more Resistant to Pests and Diseases Help Preserve the Balance of Natural Ecosystems Provide Cover and Food for All Wildlife Species Serve as Host Plants for Native Insects Provide Correct Nutrition for Wildlife, Particularly Birds. 2
Following Are Some Commonly Used Non-Native Invasive Plants with Some Native Replacements. NON-NATIVE INVASIVE TREES: Bradford Pear - Pyrus calleryana Bradford and other varieties Bred as sterile, they can be pollinated by other pear trees. Fruits are eaten by Starlings which spread the seeds. Trees are prone to splitting and are not a good investment. Norway Maple Acer platanoides Princess Tree Paulownia tomentosa Mimosa, Silk Tree - Alizia julibrissin Paper Mulberry Broussonetia papyrifera White Mulberry Morus alba Sawtooth Oak Quercus acutissima NON-NATIVE INVASIVE SHRUBS Autumn or Russian Olive - Elaeagnus umbellata Border Privet Ligustrum obtusifolium Chinese Privet L. sinense European Privet L. vurgare Japanese Privet L. japonicum Burning Bush Euonymus alatus Japanese Barberry - Berberis thunbergii Serviceberry/Shadbush Amelanchier Canadensis Downy Juneberry A. arborea Flowering Dogwood Cornus florida Sourwood Oxydendrum arboretum Winter King Hawthorne Crataegus viridus or Washington Hawthorn C. phaenopyrum Red Maple Acer rubrum Black Gum Nyssa sylvatica Redbud Cercis Canadensis Red Mulberry Morus rubra Hackberry - Celtis occidentalis American Basswood Tilia americana Any Native Oak - Quercus species Red Oak Q. rubra Northern Red Oak Q. borealis White Oak Q. alba Fringetree Chionanthus virginicus Gray Dogwood Cornus racemosa Buttonbush Cephalanthus occidentalis Arrowwood Viburnum dentatum Red or Black Chokeberry Aronia arbutifolia or melanocarpa Spicebush Lindera benzoin Blackhaw - Viburnum prunifolium Virginia Sweetspire Itea virginica Highbush Blueberry - Vaccinium corymbosum Maple-Leaf Viburnum - Viburnum acerifolium Silky Dogwood Cornus amomum 3
Exotic Bush Honeysuckles Lonicera species Multiflora Rose Rosa multiflora Wineberry Rubus phoenicolasius Butterfly Bush Buddleja species Spicebush Lindera benzoin Sweet Pepperbush - Clethra alnifolia Mountain Laurel Kalmia latifolia Swamp Rose Rosa palustris Pasture Rose R. Carolina Virginia Rose R. virginiana Common Blackberry Rubus allegheniensis Flowering Raspberry R. odoratus Joe Pye Weed Eupatorium spp. New York Ironweed Vernonia noveboracensis Milkweeds Asclepias species NON-NATIVE INVASIVE VINES English Ivy Hedera helix English Ivy was introduced to America by early settlers and has been greatly overused in the landscape. It blooms and sets seed when it reaches light. Keep it cut off the trees or supports. The vines smother trees and on the ground prevent birds from digging through the vines for food. Seeds are spread by Starlings. Japanese Honeysuckle Lonicera japonica The vines strangle trees. Groundcover in shaded areas: White Wood Aster Eurybia (Aster) divaricatus. Wild Ginger - Asarum canadense FERNS: Lady Athyrium filix-femina Christmas Polystichum acrostichoides Hayscented Dennstaedtia punctilobula To hold hillsides see GRASSES Virginia Creeper Parthenocissus quinquefolia American (Trumpet) honeysuckle Lonicera sempervirens Trumpet Creeper Campsis radicans Porcelainberry Ampelopsis brevipendunculata Chinese Wisteria Wisteria sinensis Japanese Wisteria W. floribunda Periwinkle Vinca Minor Grows vigorously for form a dense mat that displaces and excludes most other plants. Passionflower - Passiflora incarnate Yellow Passionflower P. lutea American Wisteria W. frutescens Crossvine Bignonia capreolata Creeping Phlox Phlox stolonifera Foam Flower Tiarella cordifolia Dwarf Crested Iris Iris cristata Green & Gold Chrysogonum virginiana 4
NON-NATIVE INVASIVE HERBACEOUS PLANTS Lesser Celandine Ranunculus ficaria Celandine (Wood) Poppy Stylophorum diphyllum Purple Loosestrife Lythrum salicaria Grows in ordinary garden soil but will travel to wet areas. Produces a toxin that may kill other plants and small creatures in wet areas. Please remove from the landscape. Exotic Bamboos Bambusa, Phyllostachys, Pseudosasa Chinese Silver Grass - Miscanthus sinensis Pampas Grasses Cortaderia spp. Common Reed Phragmites australis Common Day Lily Hemerocallis fulva (The orange one) Great Blue Lobelia L. siphilitica Cardinal Flower Lobelia cardinalis Gayfeather, Blazing Stars Liatris spp. Summer Phlox Phlox paniculata Vivid False Dragonhead Physostegia vriginiana Vivid Indiangrass Sorghastrum nutans Switchgrass Panicum virgatum Red Osier Dogwood Cornus sericea Little Bluestem Schizachyrium scoparium Bushy Beardgrass Andropogon glomeratus Smooth Cordgrass Spartina alterniflora There are no native daylilies but there are thousands of hybrids which are not invasive choose one of those. There are many, many more species of native plants that could and should be used in place of exotic (not locally native) plants even if the exotics are not invasive. These non-native invasive plants have been carried in unintentionally or are no longer being planted. They are highly invasive and should be removed from the landscape: Stinking Sumac or Tree of Heaven - Ailanthus altissima Kudzu Pueraria Montana Mile-a-minute Polygonum perfoliatum Chinese Lespedeza - Lespedeza cuneata Canada Thistle - Cirsium arvense Garlic Mustard Alliaria petiolata Japanese Stilt Grass - Microstegium vimineum 5
For more information and more complete listings of non-native invasive plants and information about native plants to use in the landscape, go to these sites. Publication on-line: Plant Invaders of Mid-Atlantic Natural Areas by the National Park Service and U.S. Fish and Wildlife Service. www.nps.gov/plants/alien/pubs/midatlantic Publication on-line: Nonnative Invasive Plants of Southern Forests. Covers as far north as Virginia and Kentucky but many of the invasive plants are also in Maryland. May be obtained from the USDA: 1-828-257-4830 http://www.srs.fs.usda.gov/pubs Publication on-line: Native Plants for Wildlife Habitat and Conservation Landscaping - Chesapeake Bay Watershed. www.nps.gov/plants/pubs/chesapeake/ Home & Garden Information site of the Maryland Cooperative Extension. Learn about Master Gardener program, order publications, invasive species alerts, send a question about your garden, links to other sites. www.hgic.umd.edu/ Cooperative regional project of natural resource professionals in the Washington Metropolitan Area. Excellent site with discussions of Non-Native Invasive Plants, their effect on environment and birds, English Ivy brochure, much more! www.invasiveplants.org Maryland Native Plant Society www.mdflora.org Virginia Native Plant Society www.vnps.org Lists native plants, sources for buying them, and plants that should not be planted. Six Steps to Turn Your Yard into a Sanctuary for Birds plus much more information about birds. http://www.backyardbirdcare.org/ Equal Opportunity Programs 6