Six Nastiest Invasive Plants

Sometimes, a certain breed of plant can take over and strangle a lawn or garden. You’ll start seeing them pop up everywhere, and like it or not, these plants are soon covering the majority of your land. You’ve been attacked by an invasive species, a problem we’re seeing more of as people try to bring in new plants without properly researching them. Thankfully, the nasty winter of the northern regions of the United States can kill off some of these species, but they can be quite resilient. Today, we’re going to look at the five nastiest invasive plants that can ruin your lawn and garden – some of these are merely nuisances, others are outright banned in many states.

invasive species

Courtesy: Scott Loarle, via Flickr

Canada Thistle/Creeping Thistle

Pictured at right, this is considered one of the most invasive plant species in the United States. It is classified as a noxious weed and a detrimental plant at a national level. It is a plant that should never be intentionally introduced to any environment, and should be killed off when seen. Oddly enough, it is a beneficial plant – finches feed on the seeds, and the roots are edible. However, the speed at which it spreads negates these benefits.


Initially introduced from Japan as an ornamental plant with many uses, no one realized just how invasive this species would get. Like the creeping thistle, it has benefits. In fact, it can be used as food for humans, food for livestock, it prevents soil erosion, and it has medicinal value. Unfortunately, it also can grow over and kill of native species by blocking light from reaching them. It isn’t gradual, either – patches of kudzu have been noted expanding at the rate of a foot per day in some cases.

Japanese Knotweed

Not only one of the nastiest invasive plants in America, this is cited by the World Conservation Union as one of the most invasive species across the globe. The biggest problem is that the root system is strong, and if not brought under control, it can damage buildings, roads, and other parts of the infrastructure. Worst of all, it tolerates temperatures below zero, runs 10 feet deep, and can’t be killed by cutting it.

Cheat Grass/Drooping Brome

Unlike many of the other invasive plants mentioned so far, this one has no beneficial uses, but it also does not pose a terrible threat to other species or to our infrastructure. It is simply a wide-spread weed. Some birds will feed on it, and sheep will also eat it, which is a good thing – cheat grass’s one problem is dries out quickly and is fuel for wildfires, as California has seen in recent years. Unlike most invasive plants, cheat grass uses air- and animal-borne seeds to spread, instead of creeping underground rhizomes.

Johnson Grass

Considered one of the ten worst weeds in the world, Johnson grass was originally introduced for foraging and to stop erosion along river banks. It has been found to cause bloat in herbivores that eat it, while wilted foliage has been found to contain hydrogen cyanide – if eaten in large amounts, it is potent enough to kill a horse or cow. It also tends to choke out crops that have been planted by farmers, making it one of the worst invasive plants for a farmer.


Aside from spreading quickly and pushing out native species, bishopweed isn’t all that bad. It is usable as a vegetable early in the year, and the leaves have sometimes been used as medicinal herbs for a variety of ailments, sometimes even successfully. It spreads incredibly fast, using underground rhizomes similar to most other invasive plants. This is especially prevalent in the Great Lakes and Northeastern regions of the United States.

So keep your eye out for these invasive plant species, and react quickly when you see them start to take hold in your garden. These species can choke out and kill of what you already have, regardless of the plant.

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Written by Andrew T for LawnEq - The specialists for Lawn Mower Parts and Small Engine Parts. We offer genuine premium OEM parts for Land Pride, Toro and many more dependable brands.