When it comes to nature, the general rule of thumb is this: The dangerous stuff looks scary, and the harmless stuff looks beautiful (or, at the very least, unassuming). So it might be a surprise, then, to learn that plants and flowers—often beautiful, always unassuming—rank among the most dangerous things on the planet. And no, we’re not just talking about the exotic blooms hiding in the Amazon—we’re referring to the very plants and herbs that grow in your own backyard. Read on to find out which dangerous plants might be lurking just a few feet away.

1.Oleander

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Known for its striking flowers in the summertime, the oleander plant also holds a deadly secret: every part of it is highly toxic. According to a 2010 study published in Heart Views, parts of the oleander plant contain cardiac glycosides, compounds that can cause acute cardiac toxicity and digestive issues. Those who ingest the plant can also suffer symptoms that range from an erratic pulse to a coma.

2.Rosary Pea

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Native to tropical areas and often found in Florida, the rosary pea is considered one of the most invasive—and one of the most dangerous—plant species. According to the Centers For Disease Control and Prevention (CDC), the plant’s seeds contain the poison abrin. And it turns out, there’s enough abrin in just one seed to kill you if swallowed.

3.White Snakeroot

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Ageratina altissima, or white snakeroot, is a poisonous herb found in North America that contains a toxic alcohol called tremetol. But just how poisonous is this plant? Well, back when explorers were first settling Indiana and Ohio in the early 19th century, it’s estimated that up to half of their deaths—including that of Abraham Lincoln’s mother, Nancy Hanks Lincoln—were caused by indirectly ingesting white snakeroot. Cattle and other livestock in the area would eat the seemingly benign herb and pass the poisonous tremetol to humans via their milk. The illness was known as fatal milk sickness.

4.American Pokeweed

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American pokeweed is found in almost every area in the U.S., save for a few states in the northwestern region. And while the plant does produce a purple-black berry known as a pokeberry, the last thing you’d ever want to do is eat one. According to the National Capital Poison Center (NCPC), consuming these can cause everything from nausea and vomiting to low blood pressure. If you have children, make sure to monitor them when they’re playing in your yard, as the NCPC notes that youngsters often mistake these berries for grapes.

5.Deadly Nightshade

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Unsurprisingly, the deadly nightshade plant is, well, deadly. Due to the alkaloids in its stems, leaves, berries, and roots, the plant is incredibly poisonous to the body. Even rubbing up against it can cause irritation to the skin, according to the Royal Horticultural Society. It would take just two berries from this plant to kill a child and between 10 and 20 to kill an adult.

6.Water Hemlock

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If you know anything about water hemlock, then it’s likely that you’re familiar with the plant’s claim to fame: killing Socrates. According to the United States Department of Agriculture (USDA), this plant contains the toxin cicutoxin, which, when ingested, acts directly on the central nervous system. In the most extreme cases, that could result in grand mal seizures and death.

7.Lily of the Valley

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This perennial outdoor ornamental herb, a popular staple of outdoor gardens everywhere, can actually be incredibly toxic, according to the Canadian Biodiversity Information Facility (CBIF). Its toxicity comes from the cardiac glycosides and saponins present in the plants, which can affect the heart if eaten. Lily of the valley is so toxic, in fact, that the CBIF notes cases where both people and animals have fallen ill by merely drinking water the plant was in.

8.Rhubarb

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Sure, it’s great in rhubarb pie, but ingesting large amounts of this plant’s leaves can kill you, according to the BBC. Because it contains deadly oxalic acid, ingesting too many rhubarb leaves can cause kidney failure. Thankfully, experts at the University of California, Santa Clara note that you’d have to eat some 12 pounds of rhubarb to really get sick.

9.Foxglove

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The foxglove plant produces digoxin, an active ingredient in medications that prevent heart failure. According to the NCPC, by ingesting foxglove, you’re essentially “taking an unregulated dose of heart medicine,” which can, ironically, cause heart failure. As such, you should keep this plant far, far away from children and animals.

10.Wisteria

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When it comes to dangerous plants in your backyard, wisteria is one of the worst ones there is. According to one case study from the Santa Clara Valley Medical Center, the wisteria plant can cause headaches, gastroenteritis, hematemesis, dizziness, confusion, diaphoresis, and, frighteningly, syncopal episodes (or temporary drops in blood flow to the brain that result in a loss of consciousness and control of the muscles). These symptoms typically last for five to seven days after eating more than a few berries from the plant—if they don’t kill you, that is.

11.Dieffenbachia

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When it comes to dieffenbachia, it’s small children and pets that you should be concerned about. Why? Well, both your animals and your youngsters can’t differentiate a dangerous backyard plant from a snack, and they are therefore the most likely to take a big bite out of a dieffenbachia leaf. If your pet or small child does ingest a dieffenbachia leaf containing insoluble calcium oxalate crystals, they will experience excessive drooling, oral pain, vomiting, and a decreased appetite.

12.Daffodil

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If you seek help quickly, ingesting daffodils won’t kill you. However, according to the NCPC, ingestion can be fatal to small children and pets if left untreated. And while all parts of a daffodil contain the toxic chemical lycorine, it’s the oxalates—or toxic chemicals found in the plant’s bulb—that do the most damage to your body. If you experience throat pain, difficulty swallowing, and severe drooling that persists for several hours, get thee to a doctor, stat.

13. Hydrangea

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As far as the poisonous nature of the popular hydrangea plant is concerned, only the flower buds are truly harmful when ingested, according to the Canadian Biodiversity Information Facility. If consumed, humans can experience an upset stomach, skin irritation, and, in more serious cases, convulsions and coma.

14. Rhododendron

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The honey produced (and sometimes eaten) from the common rhododendron plant is also called “mad honey”—and for good reason. According to the NCPC, the toxins found in the plant cause confusion in those who ingest it, along with dangerously low blood pressure and sometimes even death. (Fun fact: The earliest case of rhododendron poisoning is said to have occurred in the first century B.C.E. when Roman troops were allegedly poisoned with its honey. The day after they were poisoned, they were so confused that they lost a battle.)

15. Yew

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In ancient cultures, yew is also called the “tree of death,” as it was once used as an offering to the gods of death. And there’s a reason why: According to Cornell University’s Department of Animal Science, the yew plant, found in all corners of the world, is dangerously toxic. No matter how you consume the plant, its toxins have the potential to cause cardiac arrhythmia and stop your heart entirely. Animals that eat the plant are often found deceased next to it just 24 to 48 hours after consumption.

16. Philodendron

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Due to the relatively minimal care required to maintain philodendron plants, they’re commonly found in backyards all over the country. However, as reported by ABC News, they contain a toxin in their leaves called calcium oxalate that can cause inflammation of the mucous membranes in the mouth and throat when ingested. Though it’s not deadly in most cases of ingestion by humans, it can prove fatal to smaller children and pets—and the more they eat, the worse off they are.

17 . Devil’s Helmet

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Just a few years ago, a gardener died after simply brushing up against a devil’s helmet plant. And believe it or not, the plant’s exterior isn’t even its most poisonous part. As poison expert John Robertson told BBC News, the most poisonous part of the plant is actually its roots, as ingestion of this specific part causes heart failure. Most fatalities, he says, occur within the first few hours of eating the plant’s roots.

18. Tulips

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Tulips might make your garden shine, but they also have the potential to poison your pet. According to the ASPCA, this plant is toxic to dogs, cats, and horses in its bulb especially, and symptoms of ingestion range from vomiting and diarrhea to hypersalivation and depression.

19. Poison Ivy

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As its name suggests, poison ivy is, well, poisonous. Found all over the United States, this plant contains a resin called urushiol that causes an epidermal allergic reaction characterized by redness, itching, and swelling. If the plant sets on fire and you inhale the smoke, it can also affect your breathing.

20. Angel’s Trumpet

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Angel’s trumpet is a tropical plant known for its Bugle-shaped flowers. And while it’s aesthetically pleasing, the last thing you’d ever want to do is find out what it tastes like: As one 2008 case report published in Paediatrics & Child Health notes, ingestion can cause dangerous hallucinogenic symptoms like loss of consciousness and delirium