Known as deadly nightshade (and for good reason), Atropa belladonna is one of the most toxic plants in the Western Hemisphere. The dark purple, bell-shaped flowers cause hallucinations and even death if consumed, and just brushing up against its leaves is enough to cause blisters. Exercise caution if you spot the plant in your yard, and get rid of it immediately.

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While not as toxic as its cousin belladonna, bittersweet nightshade is poisonous to pets and can be deadly to children who eat its brilliant red berries. This perennial vine flowers from mid-May to September with pretty clusters of purple flowers. If you have kids or pets, stay on the safe side and banish the plant from your lawn and garden. 

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Also known as poke root and pokeberry, pokeweed is a perennial that can grow six to eight feet tall. It’s festooned with white clusters of flowers that give way to shiny berries that attract birds. Every part of this plant is harmful, especially the roots, and contact can cause anything from vomiting to internal bleeding. Even worse, pokeweed is invasive and difficult to eradicate. For the best chance of success, take swift action if you notice the weed on your property.

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Like poison ivy, poison oak grows three-leaf clusters that can cause severe dermatitis and intense itching. This plant can appear as a shrub or a climbing vine, and it's often found in both the western and southeastern United States. If you're planning on getting hands-on, be careful and make sure to wear gloves and protective clothing.

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Jimson weed, also called devil’s snare, is loaded with deliriant toxins. The roots, stems, leaves, and seeds are all dangerous if ingested, and they can cause terrifying hallucinations, hyperthermia, erratic heart rhythms—even death. Believed to have originated in Mexico, it has now adapted to survive in cooler climes of North America.

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Giant hogweed is part of the carrot family but has none of the good qualities of the vegetable. Growing up to 14 feet tall, with leaves that span up to 5 feet, it’s topped with flowers so beautiful you might want to reach out to touch them—but don't! The sap of giant hogweed is phototoxic, and it can cause skin irritation and blistering that can result in scars that last for years. If you find the wily weed, call your county’s environmental agency immediately. It’s toxic and invasive, and it must be handled with great care.

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Even more toxic than poison ivy and poison oak, poison sumac packs a serious punch. If you brush against a plant, you can expect rashes, oozing blisters, and mucous membrane irritation. It grows most commonly in the southeastern United States, specifically in boggy swamp areas. Unlike poison ivy and poison oak, it has leaves that grow in clusters of 7 to 13, with bunches of green berries drooping from its stems.

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The seeds of the castor bean are among the deadliest on earth, and they are hazardous to both people and pets. While some varieties are intentional additions to ornamental gardens, castor bean also grows as a weed that can reach 15 feet tall. The main toxin in the castor bean seed is ricin, which has been used as a chemical or biological warfare agent. Avoid growing it at home if you have pets or children.

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Most famously used to poison Socrates, poison hemlock has no relation to the evergreen hemlock tree. Its fringy leaves can be easily taken for parsley—a dangerous mistake if ingested. If you find the weed on your property, it’s best to remove it carefully while taking precautions, as its toxins can also be absorbed by the skin.

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No list of poisonous weeds would be complete without a nod to the nemesis of campers, gardeners, and hikers alike: poison ivy. Growing throughout much of North America, poison ivy causes a rash upon contact that’s accompanied by severe itching and blistering. Its trademark hairy vine is punctuated by three-leaf clusters and white berries. Considered a noxious weed, poison ivy should be eradicated from your property by either pulling it out (while wearing protective clothing and gloves) or spraying it with herbicide.

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