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Ah, daffodils. Those cheery, usually yellow, symbols of spring… they're also cold-blooded killers.

They're not only toxic to us and our pets—they're toxic to other plants! But turns out, there are some big reasons to be thankful for that. All plants in the genus Narcissus (otherwise known as daffodils) are poisonous from bulb to bloom.

We've actually talked about their toxicity before, because one chemical they have, lycorine, poses a threat to people and pets. But it turns out these flowers also kill their petaled peers. If you put fresh-cut daffodils in the same vase as, say, tulips or roses, you'll notice the other flowers quickly become wilted and their leaves yellowed.

And I do mean “quickly.” A daffodil can reduce a rose's vase life from eleven days down to three, or a tulip's vase life from seven days to four. Florists call this the “vase effect.” And it's thanks to the daffodil's stems. They're full of a toxic sap called mucilage, so when the flowers are cut, sap flows from the stem.

This wouldn't be so bad, except that when they're put in the same vase, other flowers use their stems as straws to suck up water—and whatever's in it. Like poison. Different parts of the mucilage can kill different flowers, too.

Roses, for example, are done in by its sugar—though, indirectly. See, the sugar is a feast for bacteria in the water, and since rose stems don't have much of a microbiome to protect them, those bacteria can get inside and plug them up, keeping the flower from getting enough water. Meanwhile, species like tulips have to contend with narciclasine.

That's an alkaloid—so it's in the same class of molecules as caffeine and nicotine. And while it's not exclusive to daffodils, it's still bad news —research has shown that it can kill plants in a bunch of ways. It inhibits cell division and protein synthesis—both of which are kind of deal breakers for staying alive.

And it can interfere with the plant growth hormone auxin. So, narciclasine can jam almost all of the signals that poor tulip needs to stay beautiful. Luckily, florists get around the daffodil's penchant for destruction by putting them in a separate vase for at least a few hours to draw out the sap.

Then, when their water is replaced, most of the toxic stuff is washed away. More will leak if you cut or otherwise wound the stems again, though. And... you might not want to toss the mucilage at all.

Because some plants actually seem to like it. Irises, for example, live longer when paired with daffodils. It seems that for them, narciclasine prevents the production of enzymes and other proteins involved in aging, allowing the flowers to last longer.

And irises might not be the only species to benefit from the daffodil's sap. The father of medicine, Hippocrates, used salves of Narcissus oil to treat cancer, of all things — way back in the 4th and 5th Century B. C.

E. And narciclasine's antitumor potential was recognized when it was isolated in the 1960s. So now, researchers are taking a closer look to see if its ability to impede cell growth and survival could make it useful for managing and treating cancers.

So yeah—daffodils are surprisingly feisty. And that's part of what makes them great. Thanks for watching this episode of SciShow!

If you enjoyed learning about this killer plant, you'll probably love our list show of poisonous plants you might have around your house. And if all this flower science has your love of fun science videos blooming, you can click the subscribe button and ring the notification bell! [♪ OUTRO].