The Debunker: Does Every Rose Have Its Thorn?

by Ken Jennings

Spring is turning to summer here in the Northern Hemisphere, and the world is in blossom. Flowers always make me think of Chairman Mao, who once vowed to “let a hundred flowers bloom” in China, meaning that the nation would be healthier if a diversity of ideas could compete for attention. But in real life, sometimes the wrong flowers win the war of ideas, leading us up a primrose path of misconceptions and misinformation. This month, Jeopardy! champ Ken Jennings digs up all kinds of floral falsehoods from the fertile soil of his mind, separating the weeds of legend from the pick-me-up bouquet… of truth.

Flower Myth #4: Every Rose Has Its Thorn.

I hate to second-guess the musical genius of Poison, especially since astronomers have proven that every night has its dawn, and I have to assume that every cowboy sings a sad, sad song at least occasionally. But, surprisingly, rose plants don’t have thorns—botanically speaking, that is.

In technical terms, a thorn isn’t just any pointy part of a plant: it must be a specially adapted stem or branch, like the sharp tips of a hawthorn shrub. Spines are modified leaves, like the pointy things that cover cacti. What roses (and blackberries and many other common plants) have instead are called prickles—specially modified hairs. Prickles, unlike thorns and spines, don’t contain vascular tissue. All three structures probably evolved for the same purpose—a defense mechanism against hungry herbivores—but they have very different morphologies.

Thorns aren’t the only case where popular and botanical definitions of the same word can be very different. For example: have you ever pulled the petals off a daisy? No you haven’t! Petals are parts of a single flower’s corolla, but the head of a daisy is technically made up of lots of individual flowers: the “disk flowers” in the center surrounded by “ray flowers” around the outside. No petals anywhere—each of the white things is its own flower. I guess what I’m saying is that botanists are a huge bunch of killjoys and if the guys from Poison ever run into them in a dark alley sometime, there’s gonna be trouble.

Quick Quiz: What island are you visiting if the local alphabet still includes the thorn, an old runic letter for the “th” sound?

Ken Jennings is the author of Brainiac, Ken Jennings's Trivia Almanac, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at or on Twitter as @KenJennings.

Photo by Flickr user DBduo Photography. Used under a Creative Commons License.