After all, plenty of edible and perfectly tasty parts of plants, like red beet greens, often get composted simply because people never think of eating them.
But before you go sampling all the cast-off roots, stems, and seeds in your kitchen, know that sometimes there are good reasons these things don’t routinely show up on our dinner plates—usually because they are, in fact, dangerous to eat. Here are seven produce scraps that are better left in the compost bin.
Potatoes belong to the nightshade family of plants, all of which contain the toxic compound solanine. In fact, the Scottish king, Macbeth famously used the potato’s cousin belladonna—commonly called “deadly nightshade”—to poison his Danish enemies. (Shakespeare gives the event a nod in his play Macbeth.) In potatoes, solanine is mostly concentrated in the stems and sprouts, so you should always cut off any shots before cooking (though you’d have to eat a lot to get really sick). Selenium is especially concentrated in green potatoes.
The tomato, the potato’s close cousin, belongs to another branch of the nightshade family tree. Tomatoes were feared in Europe for more than 200 years after they were introduced from the Americas and were used for ornamental purposes only up until the 1800s. The leaves contain trace amounts of selenium and tomatine, which could leave you with an upset stomach if you eat a lot of them at once (it would take eating at least a pound for a fatal dose).
As you may have heard, apple seeds contain the poison cyanide. More specifically, they contain amygdalin, a substance that releases cyanide when it comes into contact with digestive enzymes in your gut. Apple seeds’ strong outer coating usually prevents this from happening, unless you chew them up really well before swallowing. You’d have to eat about 200 well-chewed apple seeds to receive a fatal dose of cyanide. Still, you’re better off just spitting them out—they don’t taste that great anyway.
If you’ve ever grown asparagus, you know the female plants develop some very tempting red berries. (Most modern hybrids are male plants and won’t produce the berries.) But don’t touch them! These berries are unlikely to kill you, but they can make you feel very ill due to the presence of sapogenins, a type of compound that is mildly toxic to humans and poisonous to animals. If eaten, you can expect vomiting and diarrhea.
The stalks make a tasty summer pie when combined with sweet strawberries, but eating the leaves might mean a trip to the emergency room. Rhubarb leaves contain oxalic acid and anthraquinone glycosides, two compounds that are poisonous to humans when ingested. The symptoms vary depending on how much you eat, but they include everything from vomiting and stomach pain to possible seizures.
Related: Strawberry-Rhubarb Galette
Eggplant Leaves and Flowers
Eggplant is another member of that infamous nightshade family. Sometimes people are under the impression that eating raw eggplant is poisonous, which isn’t true. However, the leaves and flowers of eggplants will probably make you sick, as that’s where most of the toxic solution is concentrated.
Just about all parts of the elderberry tree are toxic to humans and animals, especially the roots, leaves, bark, and branches—but also the berries and flowers. All parts of the plant contain compounds that can produce hydrocyanic acid, which releases cyanide. Cooling off the cyanide-producing compound is recommended when consuming the flowers and berries, and you should avoid the rest of these flowering trees entirely. Eating unripe, uncooked berries can cause nausea and vomiting, so be careful to follow recipe directions instead of experimenting.