Invasive Plant Species

Last edited January 14, 2003

By Hubert Ling

As explained in the movie "Jurassic Park", contained within the coils of DNA is one of the mightiest powers on earth. Coded with a simple alphabet of A, T, G, and C is the power to kill billions of organisms, change the gas concentration of the atmosphere, and yes even destroy the whole earth with a nuclear Winter.

By carelessly shifting around organisms, with their awesome genetic potential, we have caused major ecological disasters. Gone is the most important tree in the Northeast, the American Chestnut, our premier landscaping tree, the American Elm, and gone are huge tracts of productive fresh water marsh. Now these marshes contain only monocultures (only one species present) of purple loosestrife.

Cornell ecologist David Pimentel has estimated that alien species annually cause $138 billion dollars of damage to our US economy; an estimated 50,000 alien species of insects, plants and other pests now crowd our shores. The US government spent $37 million in 2000 to attempt to alleviate some of the harmful effects of invasives but that amount has done little to control the problem.

The basic problem is that all organisms have been programmed with a reproductive capacity that can easily outstrip all available resources. This humungous genetic potential is generally held in check by competition with dozens if not hundreds of other organisms, which also have similar genetic potentials. With so much competition, no one organism takes it all; generally each organism takes only a small share of the total resources of land, water, minerals, light etc.

In addition to direct or indirect competition for resources, disease agents control population growth of any one species. If any one organism grows very well, very large populations develop of that one species. These large populations are very susceptible to attack by disease agents, which include fungi, viruses, and bacteria. Disease agents spread rapidly when their hosts grow close together.

Thus, in any community a dynamic balance is maintained, where populations often ebb and surge but monocultures are rare and populations whose numbers have dwindled are under less stress and eventually recover. Native plants in any given area have adapted to all the other organisms in a given area and genetically diverse ecosystems are generally maintained.

A different scenario takes place when an alien species is transported to a new area. Although direct competition with similar species is still a problem, the new kid in the block may have no natural pests and diseases. Thus, large stands of monocultures can occur. It is generally accepted that one plant species will support 10 species of animals. If one species takes over 99% of a given habitat dozens if not hundreds of species are lost from that area and some populations are stressed enough that extinction is possible.

Humans are responsible for almost all of the invasive plant and animal problems. Many of our problem invasives were (and often still are) planted as landscape plants in New Jersey. These include: Norway Maple, Japanese Barberry, Asian Bittersweet, English Ivy, Mimosa, Wisteria, Japanese Honeysuckle, Bugleweed, Bamboo, Day Lily, Purple Loosestrife, Tansy, and Dame's Rocket.

Only a relatively few commercially important plants such as teasel, which was used in colonial days to raise the knap on woolen garments and spearmint, show much of a tendency to persist and multiply in the wild. We should probably include in this short list the important pasture clovers: White Sweet, White, and Red as plants that have become so common most people would think that they have been here forever.

Other plants have escaped local and federal projects: Multiflora Rose (previously used as crash barriers along highways, Crown Vetch (still used to stabilize steep hillsides, and Russian and Autumn Olive (used for wildlife habitat support).

We will probably never know how most of the alien plants arrived here. Many may have arrived as contaminating weed seeds along with seed stocks. It is very probable that the following list of plants arrived by that route: Common Mullein, Moth Mullein, Buttercups, Spotted Knapweed, Ox-eye Daisy, Queen Ann's Lace etc.

What can you do to help? Plant only native plants. How would you feel if you started a several billion-dollar problem such as Purple Loosestrife? Definitely avoid plants in categories 1 and 2 and support legislation to restrict these plants. Join the Native Plant Society or other conservation groups. Other sources of information include the New Jersey Department of Agriculture Invasive Weed Council, Invasivespecies.gov , and The Nature Conservancy.

Listed below are the scientific and common names for problem invasive plants for NJ. These lists are not complete and we would like additions, modifications and suggestions. This list will be updated.

Category 1, Strongly Invasive and Widespread
type scientific name common name    
Herbaceous Dicot Achillea millefolium Yarrow
Herbaceous Dicot Alliaria petiolata Garlic Mustard
Herbaceous Dicot Artemisia vulgaris Mugwort
Herbaceous Dicot Cichorium intybus Chickory
Herbaceous Dicot Coronilla varia Crown Vetch
Herbaceous Dicot Daucus carota Wild Carrot
Herbaceous Dicot Glechoma hederacea Gill over the ground
Herbaceous Dicot Hesperis matronalis Danes Rocket
Herbaceous Dicot Lythrum salicaria Purple Loosestrife
Herbaceous Dicot Malva moschata Musk Mallow
Herbaceous Dicot Meliotus alba White Sweet Clover
Herbaceous Dicot Plantago lanceolata English Plantain
Herbaceous Dicot Polygonium cuspidatam Japanese Knotweed
Herbaceous Dicot Rumex crispus Curly Dock
Herbaceous Dicot Trifolium pratense Red Clover
Herbaceous Dicot Trifolium repens White Clover
Monocot Allium vineale Field Garlic
Monocot Arundinaria bambusa Any Hardy Bamboo
Monocot Dendrocalamus Bamboo
Monocot Cynodon dactylon Bermuda Grass
Monocot Dactylis glomerata Orchard Grass
Monocot Digitaria sanguinalis Crab Grass
Monocot Echinochloa crusgalli Barnyard Grass
Monocot Hemercallus fulva Day Lily
Monocot Microstegium vimineum Japanese Stilt Grass
Monocot Phragmites australis Common Reed
Woody Plant Acer platanoides Norway Maple
Woody Plant Alianthus altissima Tree of Heaven
Woody Plant Berberis thunbergii Japanese Barberry
Vine Celastrus orbiculatus Asian Bittersweet
Woody Plant Elaeaghus angustifolia Russian Olive
Woody Plant Elaeaghus umbellata Autumn Olive
Vine Hedera helix English Ivy
Vine Lonicera japonica Japanese Honeysuckle
Woody Plant Rhamnus cartharticus Buckthorn
Woody Plant Rhamnus frangula Alder Buckthorn
Woody Plant Rosa multiflora Multiflora Rose

Category 2, Invasive But Not As Widespread (Yet)
type scientific name common name    
Herbaceous Dicot Ajuga reptans Common Bugleweed
Herbaceous Dicot Centaurea maculosa Spotted Knapweed
Herbaceous Dicot Chelidonium majus Celandine
Herbaceous Dicot Chrysanthemum leucanthemum Ox-Eye Daisy
Herbaceous Dicot Dianthus armeria Depford Pink
Herbaceous Dicot Galinsoga ciliata Galinsoga
Herbaceous Dicot Lamium purpureum Purple Dead Nettle
Herbaceous Dicot Linaria vulgaris Butter-and-Eggs
Herbaceous Dicot Lysimachia nummularia Moneywort
Herbaceous Dicot Matricaria matricariodes Pineapple Weed
Herbaceous Dicot Mentha spicata Spearmint
Herbaceous Dicot Polygonum persicaria Lady's-Thumb
Herbaceous Dicot Portulaca oleracea Purslane
Herbaceous Dicot Ranunculus acris Common Buttercup
Herbaceous Dicot Ranunculus bulbosus Bulbous Buttercup
Herbaceous Dicot Ranunculus ficaria Lesser Celandine
Herbaceous Dicot Ranunculus repens Creeping Buttercup
Herbaceous Dicot Rumex acetosella Sheep's Sorrel
Herbaceous Dicot Rumex obtusifolius Broad Dock
Herbaceous Dicot Verbascum thapsus Common Mullein
Herbaceous Dicot Verbascum blattaria Moth Mullein
Monocot Commelina communis Day Flower
Woody Plant Albizia julibrissin Mimosa
Woody Plant Prunus avium Crab Cherry
Vine Wisteria frutescens Wisteria
Vine Wisteria floribunda Wisteria