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In the next century, the greatest threat to our native plants and the wildlife species that depend upon them may well come from other plants. Thousands of plant species have been brought to North America in the past three centuries. Most are well-behaved, rarely penetrating natural areas. Several hundred, however, have no natural controls here, and are able to out-compete and gradually displace our native plants, even deep in forests and undisturbed ecosystems. Variously called alien, introduced, or exotic, these non-natives are highly invasive.
Some of these plants were brought here intentionally, for their medicinal, ornamental, or food value. Others hid in soil, crop seed, or ballast. Most came from other continents, but a few have spread from other parts of the US. In each region, different species are better adapted and therefore pose a greater threat. This guide is for the piedmont and inner coastal plain regions of Maryland, northern Virginia, the District of Columbia, Delaware, and southeastern Pennsylvania.
Many of the plants in this guide are popular, even beloved, landscape plants, but it is now clear that they pose a threat to our environment. If you cannot effectively contain these plants within your property, by clipping seeds, fruits, or runners, PLEASE CONSIDER REMOVING THEM. It is a difficult decision, but each of us has a responsibility not to damage the local ecosystem that cleans our air and water, stabilizes the soil, buffers floods, and provides food and shelter for innumerable species besides our own. EACH OF THE NON-NATIVE PLANTS IN THIS GUIDE SIGNIFICANTLY REDUCES THE NUMBER OF PLANT AND ANIMAL SPECIES ON ANY SITE IT INVADES.
When evaluating exotic plants for your garden, ask these questions:
Does it naturalize or self-sow? How far does it spread? Are the seeds spread by wind or water? If so, don't plant it unless you are prepared to remove all seeds, every year.
Is it a wildlife food plant? If the answer is yes, wildlife will spread it to woods and wetlands. In other words, these are plants to avoid. Plant natives instead.
Is it a rapidly spreading ground cover? If so, don't plant it adjacent to open space.
Is it low maintenance - hardy, tolerant of drought or flooding, shade-tolerant, pest-free? If so, it has no natural controls here. Do not plant it if it can spread out of the garden.
Does it have the ability to kill or suppress growth of surrounding plants by shading them out, chemically poisoning them, or out-competing them for food and water? (Norway maple, a common landscape tree, is a prime example.) If so, you don't want it in your garden anyway!
This guide lists garden plants and weeds which are already causing significant changes to natural areas in the Mid-Atlantic. Measures for controlling each species are indicated by number, e.g., (3), in the text with a full explanation at the end of this article. Click on the word Control: to jump to that section. Then click your "back" button to return to the text. Following each section suggested alternative plants are given. These alternatives are native plants, well adapted and needing little care, attractive to birds and butterflies, and an important part of the food web for our indigenous species.
Maryland Invasive Plant Species Guide
This guide lists garden plants and weeds which are already causing significant changes to natural areas in the Mid-Atlantic. Measures for controlling each species are indicated by number, e.g., (3), in the text with a full explanation at the end of this article. Click on the word Control: to jump to that section. Then click your "back" button to return to the text. Following each section suggested alternative plants are given. These alternatives are native plants, well adapted and needing little care, attractive to birds and butterflies, and an important part of the food web for our indigenous species.
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