When you look at a plant, your first thought is probably not, “That thing’s gonna kill me!” But in some cases … that thing’s gonna kill you. Sure, plants can be pretty or delicious. But they’ve also evolved with all kinds of compounds inside them -- and sometimes, those compounds don’t play well with human biology. Whether it’s the seeds, the berries, or the whole darn plant, you’re going to want to stay away from these, no matter what. This is SciShow List Show.   [Music Playing]   Let’s start with dumbcane, a common houseplant with a hilarious name... and a particularly gruesome way of injuring people. It’s easy to grow and nice to look at, but if you eat any of this stuff you’ll end up with blisters and swelling in your mouth and throat that can make it difficult to breathe or speak -- hence the name. You also won’t want to get the sap anywhere sensitive, like in your eye, where it can cause similar kinds of damage. The problem mainly comes from tiny crystals of calcium oxalate, an acid that’s a major component of kidney stones. The crystals are shaped like needles, and they’ll easily stab through the tissues in your digestive system or eyes like some kind of poisonous acupuncture. Botanists think the needles might also contain enzymes that mess with the proteins in your cells, which help make the swelling and burning worse. The effects can last for up to two weeks, and can be fatal if the airway gets blocked -- though deaths from dumbcane are relatively rare. But seriously, why… why would you keep this plant in your house?   Foxglove is another common murder-plant that people own for some reason. The plant contains digitoxin, which -- you might have guessed from its name -- is toxic to humans, although it can also be used as a heart medication in smaller doses. Eating foxglove generally leads to fun symptoms like nausea, vomiting, and diarrhea, as well as confusion, hallucinations, and an irregular heart beat. It also can affect your vision, making things look blurry and yellowish. It’s thought that Van Gogh might have been experiencing this during what art historians call his “Yellow Period” -- it’s possible that he was given medicine containing digitoxin to help treat his seizures. Of course, he might have also just really liked the color yellow. Like with dumbcane, fatal cases of foxglove poisoning are rare, because most people don’t go around munching on buckets of the stuff. But it does happen.   The Pong-pong is a tree native to southeast Asia and some Pacific islands, about ten meters tall, and from the outside, it looks pretty normal. But even one seed would be enough to kill you. The tree’s seeds contain cerberin, which is similar to digitoxin in the sense that it interferes with normal heart function. It’s thankfully, not easy to ingest the seeds by accident -- they have to be removed from a harder husk first. But people who do end up with cerberin poisoning experience stomach symptoms and changes to their heart rhythm, and often die within a few hours.   Another incredibly poisonous plant that affects the human heart: oleander. Pliny the Elder wrote about it, way back in the year 77 CE, describing the shrub as deadly to livestock but a cure for snakebites. To be clear, if you ever get bitten by a snake and find some oleander nearby, DO NOT EAT THE OLEANDER! It doesn’t actually work as an antidote to snake venom, and eating it would probably just speed up the whole dying thing. Oleander contains a bunch of different poisonous compounds, but the main one is the appropriately-named oleandrin, which -- once again -- interferes with the heart’s beating and can eventually be fatal, though it usually isn’t. Other symptoms include nausea, vomiting, diarrhea, plus dizziness, disorientation, and blurred vision. So. Again. Don’t eat oleander. You’re better off taking your chances with the snakebite.   Now, I’d like to direct your attention to a book called Harry Potter and the Philosopher’s Stone. Perhaps you’ve heard of it. In Harry’s very first Potions lesson, Snape asks him about the difference between monkshood and wolfsbane. We later find out that they’re actually the same plant, also called aconite... which is actually true! But what the books don’t mention is that this plant is also incredibly poisonous, because of a complicated-looking compound known as aconitine which interferes with the human heart and brain. Pretty much any horrible symptom you can think of -- aconite poisoning causes it. People who eat aconite -- especially the roots or tubers -- can end up with muscle weakness, tingling, numbness, irregular heartbeat, low blood pressure, nausea, vomiting, and diarrhea! The poison’s often mentioned as a cause of death in ancient writings, and even these days, about 6% of people who are hospitalized with aconite poisoning die.   Hemlock is another poisonous plant that’s been made famous by ancient writings -- including accounts of Socrates’s execution, since he was forced to drink a hemlock-based poison. But people have also been poisoned by accident, since hemlock can look a lot like the wild parsnip, celery, and carrot plants. Hemlock contains a few different compounds that make it especially dangerous, but the worst of them is probably coniine, a ring of carbon atoms and one nitrogen atom, connected to a chain of carbons. Coniine interferes with the signals between neurons, and the effects are not pretty: the poison causes dizziness and trembling, slows down the heart rate, and eventually can cause paralysis. It can be fatal, because the diaphragm, the muscle that helps control breathing, also becomes paralyzed. But generally, if a modern patient can get on a ventilator to help them breathe until the poison wears off, they’ll be okay. Socrates, you may have heard, was not so lucky.   Probably the easiest plant on this list to ingest by accident is deadly nightshade, because to the untrained eye, its berries might look like blueberries. But eating deadly nightshade is not a good idea -- 10 to 20 berries can be enough to kill an adult. There’s a reason they call it “deadly.” The plant contains compounds called atropine and solanine, and sure, atropine is also used as a medication, but not in such high doses -- and not in combination with a second deadly poison. These two chemicals attack the human body in all kinds of ways, which is why deadly nightshade is another poison that causes practically every symptom possible. Like, it’s not even worth naming them all -- here’s a list. Apparently it is possible to build up a tolerance to the stuff, and history is full of stories of assassins who use their own tolerance to trick their victims into drinking poison. But I wouldn’t recommend trying any of these berries at all. Ever.   Another berry you’re going to want to avoid? The rosary pea. It looks pretty innocent -- just a bright red berry on a bush -- but it contains one of the most poisonous substances in the world. And there’s no antidote. The compound is called abrin, and it’s different from the other poisons we’ve talked about so far because it’s a protein. Abrin is what’s known as a ribosome-inactivating protein. That means that when it gets into a cell, it stops that cell’s ribosomes from functioning. The problem is, cells need ribosomes, because they make proteins. And when they can’t make new proteins, cells stop working. The stuff is so potent that just one tenth of a milligram can kill an adult. The symptoms usually set in within the first day, and start with the same gastrointestinal problems we’ve been talking about: nausea, vomiting, diarrhea. Eventually though, the victim gets to look forward to internal bleeding and organ damage, and then, in almost all cases, death.   But there are also plants that are so poisonous that people have died merely from drinking the milk of animals that ingested them, in what’s known as secondary poisoning. The white snakeroot is one of those plants. It contains a mix of compounds known as tremetol, which gets its name from the trembling it causes. You’d probably need to eat half a percent to two percent of your body weight to die from eating snakeroot, and it’s just a plain old shrub with small white flowers -- so, not the kind of plant that most people would just pick up and eat a pound at a time. However, in the nineteenth century it caused a huge problem in the American Midwest, where white snakeroot grows. People were dying, and nobody really knew why. It turned out that they were dying because their livestock were eating tons of snakeroot. Tremetol would end up in an animal’s milk, and then people would die from drinking it -- what they called milk sickness. This is actually how Abraham Lincoln’s mother, Nancy Lincoln, died in 1818. Eventually, a doctor named Anna Bixby identified the white snakeroot as the cause of the milk sickness with the help of a local Shawnee woman. People started removing it from the places where their animals grazed, which is why milk sickness is now pretty much unheard of.   The last poisonous plant on our list is sometimes called the little apple of death -- or just the world’s most dangerous tree. That’s probably an exaggeration, but at the very least, it does cause unbelievable amounts of pain. It’s known as the manchineel tree, and not only should you avoid eating it -- you shouldn’t touch it, either. Or even go near the thing. You don’t have to worry too much though, since it’s found only sparingly around the American South, in Central America, and South America. Manchineels contain all kinds of toxins, and we don’t even know what they all are yet. But we do know that they cause burning pain and irritation everywhere they touch. The tree -- and especially its sap -- will make human skin burn and blister, even if all you’re doing is standing under it in the rain. Just the smoke from burning it’s wood is enough to blind you. If you tried to actually eat the fruit, you’d experience burning, irritation, and swelling in your mouth, throat, and the rest of your digestive tract. That swelling and irritation can be dangerous all on its own, but deaths from eating manchineel fruits are rare, probably because most people don’t keep eating after the first bite. It’s also hard to get ahold of in the first place, because the tree is endangered. So we don’t really know how much manchineel fruit or sap it would take to kill a person. But -- as with so many of the other plants on this list -- we do know that the process wouldn’t be pleasant.   Thanks for watching this SciShow List Show, brought to you by our patrons on Patreon. If you want to help support this show, just go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow and subscribe!