5 Invasive Plants and Their Alternatives
Whether you’re yanking invasives or trying to avoid problems with your new purchases, here are 5 plants considered to be invasive followed by similar alternatives, many of which are native species.
Separating the Bad Weeds from the Really Bad Weeds
American soils sprout a diversity of bad weeds.
But then there are the really bad weeds – ones that threaten our food supply and ecosystems, ones that are invasive enough to overtake almost all other plants in their path, and some that are even harmful to people and animals.
The worst of these bad actors have been relegated to so-called “noxious” and “invasive” plant lists, which are compilations developed by government and other entities to curb the spread of particularly offensive weeds.
Japanese knotweed spreads so fast and so vigorously that it’s earned a spot on the Federal Noxious Weed List. Phot by George Weigel
What’s a "noxious" weed?
The federal government and most U.S. state governments have Noxious Weed Lists, which are official designations of plants considered to be especially harmful to agriculture, wildlife, recreation, the environment, and/or public health.
Landing on these lists gives government officials power to order quarantines of threatening plants and take other steps to control and eradicate them.
At the federal level, the U.S. Department of Agriculture has a Federal Noxious Weeds List that currently includes 112 species.
This rogue’s gallery includes aquatic troublemakers such as hydrilla, water spinach, arrowhead, giant salvinia, and duck lettuce, as well as scores of our worst "terrestrial" weeds, including goatsrue, giant hogweed, mile-a-minute weed, fireweed, wild raspberry, bittervine, two types of thistles, and 17 species of mesquite (Prosopis).
USDA’s Animal and Plant Health Inspection Service (APHIS) has authority to ban the import, export, and interstate commerce of all of those to keep them out of the U.S. and limit their spread within it.
Besides the national list, state governments (and some local governments) maintain their own Noxious Weed Lists, which vary based on which weeds are threats in differing climates and regions.
These agencies also have authority to officially restrict, quarantine, and control weeds they’ve placed on their noxious lists.
Some state and local lists are significantly larger than the federal list and sometimes are broken down into classes (based on a plant’s harm, spread, or potential to be eradicated) or include weeds on a watch list (i.e. potentially noxious weeds that haven’t yet arrived).
Altogether, some 700 weeds show up on various state Noxious Weed Lists – and more are being added each year.
State and local Noxious Weed Lists typically include plants that just about everybody considers to be a troubling weed (kudzu, poison hemlock, Japanese knotweed, Canada thistle, Palmer amaranth, and mugwort, for example), but they also often feature once-planted landscape plants that turned out to be harmfully invasive.
Common examples of those include tree of Heaven, multiflora rose, Japanese honeysuckle, Oriental bittersweet, and purple loosestrife.
In recent years, many states have been beefing up their Noxious Weed Lists with more current ornamentals – some of which are popular landscape plants and still sold in some states. Examples of those include Callery flowering pear trees, burning bush, Japanese barberry, butterfly bush, and some privets and honeysuckles.
Regional Noxious Weed Lists are usually handled by state agriculture departments or environmental protection agencies. To find your local list, search by your state’s name and "Noxious Weed List."
These Callery flowering pears have seeded into a natural area and are starting to overly dominate – a characteristic that’s caused the tree to become widely considered as invasive. Photo by George Weigel
What’s an "invasive" plant?
Assorted government agencies and other research and non-profit groups also maintain Invasive Plant Lists.
While many of the plants on these lists are also on official Noxious Weed Lists, invasive lists are geared for informational purposes so citizens can voluntarily decide on removal and control actions. In other words, they don’t carry the legal impact that Noxious Weed Lists do.
The National Invasive Species Council defines an invasive plant as one that’s not native to an ecosystem and is likely to cause harm to the economy, the environment, and/or people, animals, and desired plants.
To land on an Invasive Plant List, a plant not only must be “foreign,” “exotic,” or “non-native,” its negative impacts generally must outweigh any beneficial effects.
As with noxious weeds, Invasive Plant Lists can vary widely from region to region.
One region’s winter temperatures, for example, might be cold enough to head off a tropical weed’s spread, while soil types or natural predators can be factors that keep a weed that’s invasive in one area from getting out of control in another.
USDA’s National Invasive Species Information Center is a good online starting point that features free profiles of all plants that are either invasive in some parts of the U.S. or under watch for their invasive potential.
A second good national resource is the Invasive Plant Atlas of the United States. This website is a collaborative project of the National Park Service, the University of Georgia Center for Invasive Species and Ecosystem Health, the Invasive Plant Atlas of New England, and the Lady Bird Johnson Wildflower Center.
The site features maps that shows where suspect plants are invasive (or potentially so) and has a wealth of details that help with the identification, early detection, prevention, and management of invasive plants.
More localized Invasive Plant Lists can be found by searching the name of your state or region along with “invasive plants.”
