This perennial plant isn’t as toxic as some of the others on this list, but it’s still poisonous to humans and pets who accidentally ingest their red berries. The clusters of purple flowers are beautiful to look at but don’t be fooled by their beauty. A beast is lurking beneath those flowers. You’ll get headaches, a rash, hallucinations, convulsions, and possibly even death if you ingest the berries, and children are especially susceptible (King County).
One of the most striking plants in your backyard is also one of the most poisonous. Every part of the plant is highly toxic, so if you accidentally ingest even a small portion, you’re out of luck. According to Mount Sinai, a single leaf may kill an entire adult. A study published in 2010 found that the oleander plant contains cardiac glycosides, which cause digestive issues and acute cardiac toxicity. This will send your heart into an erratic rhythm or send you into a coma. People who ingest the flower also suffer from low blood pressure, weakness, blurred vision, or hives. The plant is mainly found in California (National Library of Medicine).
Pets and small children need to be extremely careful around dieffenbachia, one of the most poisonous plants you’ll find in your backyard. Taking a big bite out of one of the leaves of this plant will make them extremely ill. Symptoms include oral pain, vomiting, and decreased appetite. This is due to the insoluble calcium oxalate crystals in the leaves. If the skin or eyes are exposed, redness, swelling, and irritation may occur. The poison comes from the raphides, which are tiny, needle-like structures that may cause respiratory distress. Even though this makes a great house plant, you need to be very careful not to ingest it (Best Life Online).
Philodendrons don’t require a lot of TLC, which is why they’re commonly found in people’s backyards around the USA. Unfortunately, their leaves are toxic and contain calcium oxalate, which inflames the mucous membranes of the mouth and throat if accidentally ingested. It’s worse if small children or pets accidentally ingest the leaves, and the more leaves they eat, the more toxic it is. Rarely, if the throat swells too much, it may be difficult to breathe (Queensland Government).
The poppy plant is a source of opium found in morphine and heroin. The poppy flowers are especially seen in the south of America, and can easily spread. It’s toxic because the alkaloids in the pink opium poppy flower may cause convulsions, asphyxiation, and eventually, death. The surface of the unwashed seed is especially poisonous. People may start hallucinating and suffer from confusion if they ingest the seed, so it’s especially important to be mindful of the plant if you have it in your backyard (NRE).
Lantana is a beautiful, vibrant plant with yellow flowers nestled by bright red flowers. What makes the lantana plant so toxic, though, is according to DAF, “the triterpene acids, lantadene A (rehmannic acid), lantadene B, and their reduced forms.” To feel the effects of poisoning, an animal only needs to ingest around one percent of their body weight. In cattle, the animal will experience liver damage, excessive skin sensitivity to light, and yellow discoloration of the eyes, which is also referred to as jaundice.
All species of the daphne plant have varying levels of toxicity, which is especially found in the bark, leaves, and fruit. If accidentally ingested, you’ll get ulcerations in the stomach, mouth, and esophagus. If you come into contact with the sap, you’ll get contact dermatitis. Even though daphne has a beautiful aroma, it doesn’t mean it’s beautiful to eat. Keep children and pets far away from this plant (Animal Poisons).
These trumpet-shaped flowers are quite beautiful to look at. They have a unique shape and color that’s symbolic of springtime. Unfortunately, though, they don’t represent any part of springtime if you ingest them. All of the parts of the flower are poisonous, including the stem, leaves, and pollen. They’re especially toxic for cats, in that even if they ingest a small amount, they may suffer from vomiting, increased thirst, and kidney failure (Plantura).
This poisonous plant is related to bittersweet nightshade (which is also on this list). Even though it’s not the same plant, it’s just as poisonous. Both plants leave and fruit is toxic for human consumption. Initially, the color of the fruit is green, but it changes to yellow later on in the summer and by fall, it’s a beautiful, rich orange. This color-changing fruit is not one you want to ingest, though. The unripe berries are highly toxic and potentially fatal. Don’t confuse these with another fruit you may have growing in your backyard (The Spruce).
If you live in eastern North America, you’ve likely seen Mountain Laurel in your backyard. But stay far away from this poisonous plant. It’s commonly found in wet, high mountain meadows with a lot of rain. It’s not only an attractive plant, but it’s also deadly. Immediately after someone consumes the flower, they’ll experience burning lips and throat, followed by low blood pressure, drowsiness, weakness, convulsions, and paralysis followed by death. Previously, children have been poisoned and killed by simply sucking on the flowers of the plant. If you ever come across honey made from mountain laurel pollen, stay far away from it. It’s highly toxic (FS USDA).
Though you’ll mainly see this plant in northern tropical climates, it’s full of ricin, a deadly toxin. If you chew and swallow the castor beans, you’ll feel the toxic effects of the poison almost immediately. Ricin is poisonous because it gets into the cells of a human and stops proteins from working properly. You’ll have difficulty breathing, nausea, heavy sweating, and eventually, respiratory failure and death. Ricin poisoning is a federal crime, and if detectives suspect death by ricin, it’s one of the first things they’ll look for (CDC).
One of the most poisonous and dangerous plant species in tropical areas is the rosary pea. In the plant’s seed is the poison abrin, and ingesting just one seed is enough to kill you. You’ve likely seen this seed in necklaces or bracelets before, as they’re commonly found in jewelry. But even though the seeds look beautiful, with their bright red color, they’re incredibly poisonous. If ingested, you’ll experience vomiting, abdominal pain, diarrhea, fast heart rate, hallucinations, seizures, and organ failure (Centers for Disease Control).
Water Hemlock has a sinister history. It’s known for killing Socrates. It contains cicutoxin, and when ingested, it viciously acts on the central nervous system. In worst-case scenarios, it may cause grand mal seizures and death. To poison humans or livestock, you only need a small number of toxins. It may also cause nervousness, agitation, rapid breathing, tremors, and muscle twitching (Best Life Online).
If you accidentally ingest a hydrangea, which is a common plant you’ll find in your backyard, you’ll experience skin irritation, upset stomach, convulsions, and coma. The most toxic part of the plant is the flower buds. It’s even toxic to the skin, and if touched, may cause rash or irritation. The poison comes from cyanogenic glycoside. If your pet cat happens to ingest a hydrangea, it’ll experience nausea, diarrhea, depression, breathing difficulties, and seizures (Perfect Plants).
Even though wisteria is a beautiful plant to look at, hanging from the top of a ceiling with its bright purple color, it’s one of the most poisonous plants you’ll find in your backyard. The plant contains lectin and wisterin, which, initially, will cause burning in the mouth. If ingested, it may cause dizziness, confusion, headaches, or syncopal episodes, which are temporary drops in blood flow to the brain, where you may lose consciousness. If you eat the berries from the plant, you’ll experience these symptoms about five to seven days later, if you’re still alive (Science Direct).
This bright purple plant was used to kill werewolves. The Europeans first discovered its toxicity when they dipped the tips of their arrows with the flower’s toxin and used it to kill werewolves, to stop them from eating their livestock. They contain highly toxic cardiotoxins and neurotoxins, which means they’ll affect your heart and brain. Users will get chest pain, palpitations, tachycardia, nausea, vomiting, abdominal pain, and diarrhea (Pubmed).
American Pokeweed is one of the most common plants you’ll find in America, and most likely in your backyard. Don’t be fooled by its purple-black berry, also known as pokeberry. It’s highly toxic. If ingested, you’ll experience nausea, low blood pressure, and vomiting. Children are especially susceptible, since they may mistake the berries for grapes. Even though it’s at the low end of the toxicity scale, especially compared to other plants on this list, it’s still not recommended to ingest because of the horrible symptoms (Best Life Online).
It may come as a surprise to find that tulips are poisonous, even though they probably thrive around your backyard. They’re especially poisonous to pets, like horses, cats, and dogs. If they ingest the tulip bulb, they’ll experience diarrhea, hypersalivation, depression, and vomiting. If a human ingests a tulip bulb, they’ll experience mouth and skin irritation, dizziness, and abdominal upset. People who handle tulips for work or pleasure may experience “tulip fingers.” This is an irritating rash caused by a rash called tuliposide (Poison Control).
This plant may sound like a fun time, but it’s one of the most poisonous plants you can find in your backyard. It’s highly toxic and can cause drooling, gastrointestinal bleeding, vomiting, bloody diarrhea, central nervous system signs like seizures, and kidney and liver damage. Eventually, if it’s left untreated for long enough, it may cause death. Most of the time, you’ll see these signs immediately, but they may happen several days later. If you notice any of these symptoms, especially in pets who may have ingested the flower, make sure you get immediate help (Pet Poison Helpline).
Lily of the Valley is one of the most popular plants in gardens around the world. It’s a perennial outdoor ornamental herb, which means it lasts more than two years in your garden. Even though it’s popular, doesn’t mean it’s nice. It’s a naughty plant that’s incredibly toxic, which comes from the cardiac glycosides and saponins. If eaten, it affects the heart. It’s so toxic that people drinking the water the plant was in have fallen ill. Children are especially susceptible because of their size. If ingested, people will most commonly suffer from upset stomachs, slow and irregular pulse, blurred vision, and seizures (Best Life Online).
If rhododendron is ingested, its toxins confuse, low blood pressure, and possibly death. This is due to a chemical called grayanotoxins. It’s said this chemical is a natural deterrent against insects, however, it also has harmful effects on humans. It’s referred to as “mad honey” because the Romans in the first century B.C.E. were allegedly poisoned with its honey. After they were poisoned, they were so confused they lost their battles. Typically, poisoning occurs when ingesting large amounts of the plant (Royal Botanic Gardens).
Interestingly enough, tobacco is poisonous, even if it’s the most commonly used plant in the entire world. But just because it’s popular, doesn’t mean it’s safe. It’s easy to grow tobacco in your backyard, and chances are, your heavily smoking neighbors might grow the plant. It’s known as a cardiac poison that’s also damaging to your lungs, brain, and teeth. This is probably the most poisonous plant on this list. It kills more than 5 million people every single year, which is why it’s the most poisonous. It doesn’t cause immediate fatalities like the other plants on this list, the damage from tobacco is slow-burning, exactly how you smoke it (Britannica).
Yellow dock is incredibly toxic to dogs, but they’re also toxic to humans. It’s quite easy to recognize the yellow dock, as the head of the plant looks like coffee grounds and is brown. Don’t mistake this plant for coffee, though, because it won’t give you that caffeinated effect you’re looking for. People who ingest the plant will suffer from mild poisoning that shows as gastrointestinal disturbances, like diarrhea, vomiting, nausea, and cramps. If someone ingests a large amount of the plant, it may prove fatal (Picture This AI).
All parts of the white baneberry plant are toxic. We’ll give you a little hint, too. If you ever see the word “bane” in a plant’s name, it’s likely toxic. In large quantities, the berries will cause cardiac arrest or respiratory distress, stomach cramps, and dizziness in anyone who ingests them. Typically, baneberries are red, but sometimes, you’ll come across this white-berried species in your backyard. They always say, never to eat a random berry from a bush. You never know if it’s poisonous or not (Wild Adirondacks).
This plant is called bloodroot for a good reason. Its name should be enough to deter you from getting anywhere near it. Even merely touching the plant can cause skin irritation or scabbing, due to the destruction of the tissues. If taken in large enough doses by accident, it’s incredibly toxic and even fatal to humans and pets. This is due to the alkaloids found throughout the plant, which affect the nervous system. This causes vomiting and eventually coma and death if not treated in time. Interestingly enough, many Native groups use bloodroot as a die, because of its bright red, vibrant coloring (Cornell Botanical Gardens).
You’re likely familiar with poison ivy and its toxic effects on humans. It’s even more likely you have tons of poison ivy in your backyard. With one brush of poison ivy on your skin, you’ll experience intense redness, swelling, and itching on the skin, which is caused by a resin called urushiol. And don’t be fooled by believing you’re safe if you burn the plant, because if you inhale the smoke, it may affect your breathing. If you find poison ivy in your backyard, it’s recommended you use a spray to get rid of it completely (Best Life Online).
The yew plant is found all over the world and has a rocky history. Ancient cultures referred to this plant as the “tree of death,” because it may cause cardiac arrhythmia if ingested. It will completely stop your heart and cause death. Animals are very susceptible, and if they ingest yew, they’ll die within 24 to 48 hours. Its poison comes from its highly toxic alkaloids, which are found in high concentrations of the leaves in wintertime (Mount Sinai).
The name says it all. The deadly nightshade is deadly and is one of the most poisonous plants in the world. This is due to the alkaloids found in its berries, roots, stems, and leaves. Not only is ingesting it poisonous, which may cause death if ten to twenty berries are ingested by an adult but even rubbing against it irritates the skin. If ingested, other symptoms include enlarged pupils, dry mouth, vomiting, stomach pain, diarrhea, slowed breathing, delirium, and paralysis (Best Life Online).
Stay far away from the angel’s trumpet, even if its name sounds inviting. It has bugle-shaped flowers and is very beautiful to look at, but incredibly toxic if ingested. If accidentally ingested, users will experience difficulty swallowing, thirst, vomiting, diarrhea, hallucinations, loss of consciousness, and eventually, delerium. Even the perfume alone is enough to cause a negative reaction, which includes headaches, nausea, and lightheadedness (Sharp).
People often grow tansy for its golden, bright, vibrant flowers, and by looking at this photograph, you can probably see why. It’s symbolic of summertime and happiness. Even though tansy has previously been historically used for flavoring, it contains a toxic essential oil that may kill a human. If it doesn’t kill you, it will cause liver and brain damage, and at the very least, an allergic reaction to those who touch the flower. There’s a reason we don’t recommend growing these beautiful flowers in your backyard. The risk isn’t worth the reward (Growveg).
Rhubarb pie might be your favorite dessert in the world, but there’s only a small amount of rhubarb that can be used. Ingesting large amounts of this plant’s leaves can kill you. It’ll cause nausea, difficulty breathing, and kidney stones. This is due to the deadly oxalic acid, which will eventually cause kidney failure. Luckily, you’ll need to consume 12 pounds of rhubarb to get sick, which is very unlikely to happen. You can safely put the rhubarb leaves in your compost, though, because oxalic acid isn’t absorbed by the leaves (Taste Of Home).