What's the Harm?
Invasive plants cause billions of dollars of damage each year to native habitats, wetlands and waterways, crops, and parks and other preserved areas. Some of our most endangered species fight a losing battle with invasive plants to maintain their populations.
Invasive plants can crowd out or even cause the death of native plants. Some emit toxic substances that poison the soil for all other plants. Invasives can alter a native habitat so severely that not only are native plants eliminated, but the habitat can no longer support the wildlife it once did. In wetlands, invasive aquatic plants can essentially kill off all life below the surface by blocking out sunshine and oxygen. Invasive plants in croplands can reduce crop yields by 50 percent in some cases.
Some examples of the most harmful invasives in the United States are Purple Loosestrife, which takes over wetlands so aggressively that it eliminates native flora; Kudzu, which can smother woodlands by covering every tree and blocking out all sunlight; salt-cedar or tamarisk trees with long roots that suck up large quantities of water, lowering the water table to the detriment of other plants and animals; and Cheatgrass, which takes over native sagebrush-grassland habitat and provides potent fuel for wildfires that further harm the natives.
Check the Invasive Plant Finder to get a list of invasives for your state, and avoid introducing such plants into your local area.