A weed is often called "a plant out of place," but those designated as "noxious" go far, far beyond being merely out of place. These non-native plants are a true menace that have been designated undesirable by state governments and require control and even extermination. This worst-of-the-worst plant life destroys the potential for agriculture, kills native vegetation, and starves wildlife by wiping out all edible plants on which the local ecosystem relies. Perhaps it's just survival of the fittest? They may be ugly, itchy, and dangerously thorny, but these invasive plants can out-compete any fragrant flower or fruit bearing bush for water, food, and essential nutrients. Wanted dead or alive, these are the ten most noxious weeds in the USA.
10. Solanum carolinense AKA Carolina Horsenettle
The Carolina Horsenettle's isn't a nettle at all, but a member of the poisonous nightshade family. This plant features hairy leaves, a white or purple flower, a stem covered in sharp spines capable of penetrating human skin, and bears fruit that resembles the tomato - fruit so poisonous that it can and has killed adult humans. The Carolina Hornettle is resistant to most herbicides and spreads quickly by either seed or underground rhizomes. This threatening weed is currently at large in the following 18 states: Alabama, Alaska, Arizona, California, Connecticut, Hawaii, Indiana, Iowa, Louisiana, Maine, Massachusetts, Michigan, Nevada, New Jersey, New York, Oklahoma, Texas, and Vermont.
9. Agropyron repens AKA Couch Grass AKA Twitch
Creeping across 20 North American states and provinces is Couch Grass, an incredibly fast-spreading plant that's almost impossible to eliminate from gardens and backyards. The rhizome root system, even when destroyed can sprout entirely new grass plants from each sliver that remains in soil! Couch Grass may be great for grazing mammals, caterpillars, and birds, but a nightmare for farmers and gardeners alike. Couch Grass is currently terrorizing Kansas, Louisiana, Maine, Massachusetts, Michigan, Minnesota, New Jersey, Oregon, Utah, Vermont, and Wyoming.
8. Sonchus arvensis AKA Dindle
Fragrant and capable of producing colorful dandelion-like flowers, Dindle may not seem so bad compared to the thorny and poisonous villains that make up this list, but don't let its appearance fool you! Beneath its soft, yellow surface lies a dark secret: a tap root that tunnels up to 9 feet and a vast network of rhizomes that - if not destroyed entirely - will regenerate as entirely new vegetative colonies. Even its seeds can lie dormant for years, waiting for the wind to carry it to loamy soil and bright sunshine. This fast, deceitful weed has been declared an enemy of the following states: Alaska, Arizona, Colorado, Connecticut, Hawaii, Idaho, Illinois, Indiana, Iowa, Maine, Massachusetts, Michigan, Minnesota, Nevada, South Dakota, Vermont, Virginia, and Wyoming.
7. Sorghum halepense AKA Johnson Grass
This infamous strangler chokes out all plants and cash crops on every continent with the exception of Antarctica. When it dies from heat or cold, the grass's high level of hydrogen cyanide kills grazing livestock unfortunate enough to nibble. The name "Johnson" grass comes from Alabama plantation owner Colonel William Johnson, who used the plant to halt erosion. It worked and is now one of the scariest examples of "Be careful what you wish for." NOTE: Johnson Grass and all proceeding weeds of this list can be considered a major threat to all states.
6. Cuscuta AKA Dodder AKA Devil's Guts AKA Strangleweed
Dodder isn't so much a weed as it is a violent parasite. Dodder sprouts haustorium, fungal appendages that penetrate its host's vascular system. Fully attached to the host, Dodder lets its own root die - it and the host are now one and the same. Dodder cripples trees, leaves fruit-bearing trees barren, and makes it easier for floral disease to spread. Worst of all, if Dodder is not ripped away from a host plant before choking has begun, that plant is likely lost forever.
5. Lythrum salicaria AKA Purple Loosestrife
The purple loosestrife may seem like a beautiful flowered plant, but sometimes too much purple can be a bad thing. In this case, that means completely crowding out all vegetation and wiping out cattails thus disrupting the life cycles of waterfowl, amphibians, and algae. How does it commit such a widespread holocaust? By producing up to 3 million seeds per year! Purple is the new green.
4. Carduus nutans AKA Nodding Thistle
Whereas the Purple Loosestrife wrecks ponds, rivers, and other heavily watered areas, Nodding Thistle is infamous for its blight on farmland. This weed is closely related to the dandelion but features a purple head, sharp spines, and can produce up to 120,000 seeds per plant that are dispersed by the wind. Not only has Nodding Thistle been declared a major threat to U.S agriculture, but it is also noxious to farmland in Australia, Canada, and New Zealand.
3. Euphorbia esula AKA Leafy Spurge
Leafy Spurge is a monster that can survive almost anything and spreads in very little time. Each yellow flower produces hard seed capsules that, when mature, explode. That's right; they explode and propel their seed as far away as 20 feet! Most animals won't eat Leafy Spurge because it's filled with a disgusting, milky sap that is utterly repulsive. But for those animals that do, the seed of the Leafy Spurge will pass through the digestive system unharmed. Nearly half of all U.S. States have declared Leafy Spurge a threat to agriculture.
2. Convolvulus arvensis AKA Field Bindweed
One weed to rule them all, one weed to find them, one weed to bring them all and in the darkness bind them! The first thing people notice about Bindweed is its delicate, white flowers, but behind that facade of pure intentions lies knotted, spiraling stems and arrowhead shaped leaves that twist and throttle the life out of all plant life it touches. The bindweed has decimated countless acres of cropland across the U.S., racking up losses exceeding $377 million in one year alone and has proven toxic to most grazing animals. Although its 500 seeds a year may seem small compared to other fiends on this list, consider that a Bindweed seed remains viable in the soil for up to 20 years. Because of its ever-looming threat, the Bindweed is a noxious weed in over 40 North American States and Provinces.
1. Cirsium arvense AKA Creeping Thistle
The Creeping Thistle has over 49 State and Provincial Governments quivering. It's so feared that even its native land it's seen as an injurious weed. Australia, Brazil, Ireland, and New Zealand also live in dread of this weed and almost all countries closely regulate the plant and its seeds as a contaminant. What makes this purple-headed thistle so scary is its ability to thrive anywhere and everywhere. It grows in the coldest winters, the hottest summers, and doesn't discriminate when it comes to soil. Each colony expands 6 to 12 meters per year, destroying any chance of other vegetation to flourish. It's the most prevalent weed in the northern hemisphere and it's also ... the creepiest.
