Every poisonous plant, explained.

Why ornamental garden plants and roadside weeds demand visual certainty before handling, pruning, or foraging.

Fragrant spring woodland bells containing dozens of cardiac glycosides (including convallatoxin); broad green leaves before flowering are dangerously mistaken for edible wild garlic (Allium ursinum), which smells unmistakably of garlic when bruised.

Drought-hardy highway and courtyard shrub rich in oleandrin and related cardiac glycosides throughout its leaves, flowers, sap, and twigs; even smoke or skewers cut from oleander branches have caused serious poisoning.

Every part of the yew except the red fleshy seed coat (aril) contains cardiotoxic taxine alkaloids (even the tiny seed inside the red berry is poisonous); in the 1960s, NCI researchers isolated the chemotherapy drug paclitaxel (Taxol) from Pacific yew bark.

Tall Apiaceae weed with smooth, purple-blotched hollow stems and a musty mouse-like odor (used in the execution of Socrates in 399 BCE);coniine causes ascending respiratory paralysis and is fatally confused with wild carrot or parsley.

Wetland Apiaceae considered North America's most violently toxic plant; chambered rootstocks exude yellowish oil rich in cicutoxin, a central nervous system toxin that triggers status epilepticus seizures within an hour.

Shiny black single berries in five-pointed calyces containing atropine, scopolamine, and hyoscyamine; historically used to dilate pupils in Renaissance Venice and still used as purified ophthalmic and emergency hospital drugs, yet lethal if eaten.

Spiny seed capsules and trumpet blossoms loaded with variable tropane alkaloids; recorded in 1676 at Jamestown, Virginia, causing prolonged anticholinergic delirium, hyperthermia, blindness, and fatal poisoning.

Hooded violet alpine spikes containing aconitine, which locks voltage-gated sodium channels open, causing numbness, intractable ventricular arrhythmias, and death; wear gloves when gardening around monkshood roots.

Shaded North American woodland plant containing tremetol, which passes into cow's milk to cause fatal frontier 'milk sickness' (which killed Abraham Lincoln's mother, Nancy Hanks Lincoln, in 1818) until physician Anna Pierce Hobbs Bixby identified the plant with Shawnee guidance.

Jamaica's national fruit is eaten only after pods yawn open naturally on the tree and only the yellow arils are cooked; unripe pods, pink membranes, and black seeds contain hypoglycin A, which blocks fatty-acid oxidation and causes severe hypoglycemia ('Jamaican vomiting sickness').

Glossy scarlet-and-black seeds used in beadwork contain abrin, a ribosome-inactivating protein toxin even more potent by weight than ricin; intact hard seed coats pass through unbroken, but a single drilled or chewed seed can be fatal.

Ornamental garden plant pressed commercially for ricin-free castor oil (heating during meal processing denatures the protein), whereas raw mottled seeds contain lethal ricin, used in the 1978 London assassination of Bulgarian writer Georgi Markov.

South and Southeast Asian tree whose disc-shaped seeds contain strychnine, a glycine-receptor antagonist that triggers violent, conscious muscular convulsions and asphyxiation (notoriously given in small doses to marathon runner Thomas Hicks in 1904).

Towering invasive Apiaceae reaching 10 to 15 feet with coarse bristles and purple-splotched stems; clear sap contains furanocoumarins that react with ultraviolet sunlight (phytophotodermatitis) to cause severe third-degree-like blisters and lasting skin sensitivity.

Australian rainforest stinging tree in the nettle family covered in hollow silica trichomes that inject knotted neurotoxic peptides (gympietides), locking pain-sensing sodium channels open for days or weeks.

Coastal Caribbean and Florida spurge tree whose milky phorbol-ester sap blisters skin when rainwater drips through its canopy, blinds eyes if wood is burned, and ulcerates the throat if its crabapple-like 'little apples of death' are bitten.

Three golden rules of plant safety: identify by multiple botanical traits (never apps alone), wear gloves when clearing unknown sap-bearing weeds, and never taste a wild plant you cannot verify with 100% certainty.