Mystery Plant! #732

John Nelson

Posted 7/19/23

By John Nelson

“I’m a lonely little petunia in an onion patch…”

                              Lyrics by John Kamano, Billy Faber, Maurice Merl
(Photo by Linda Lee.)

Well this one’s pretty easy, I hope. And I figured that during these really hot, sultry days, now at the height of summer, you might want something like a pretty petunia, and that’s what this Mystery Plant is, of course. And of course, there’s plenty to say about pretty little petunias.

For one thing, they belong to the tomato family, and it doesn’t matter which way you pronounce that word. The tomato family is also quite properly referred to as the potato family, as well, and again, don’t worry about pronunciation. The take-home here is that the family’s botanical name is Solanaceae, and it is a big family at that, including nearly 4,000 species around the world. The Solanaceae contains some extremely important food plants, the most well-known surely being Irish potato…not to be confused with the “sweet” potato which is quite different. Tomatoes, too, along with their cousins, the various peppers, are also important economic crops. Be aware though, that a number of members of this family are quite poisonous. Jimson weed and cultivated daturas are very dangerous if consumed. (So is tobacco, another member of the family.) A wide variety of chemical constituents, many of which are technically alkaloids, result in this toxicity. Besides their general toxicity, some of these compounds have important physiological effects on humans. For example, the European herb known as “Belladonna” produces berries containing a juice, which when dripped into the eyes, causes marked dilation of the pupils. Wide-open pupils are useful for ophthalmologists, and attractive, as well, so ladies of the Italian Renaissance would use this as a beauty technique. That’s where the name “Belladonna” (meaning beautiful lady) comes from. Anyway, many ornamental species are members of the tomato family, bringing us popular garden plants…such as this week’s summery little Mystery Plant.

If you’ve ever handled a petunia plant, you have probably noticed a sort of soft, gooey feel from the  foliage and stems…some people say “clammy”. It’s due to the presence of tiny, soft plant hairs, thousands of them, each one tipped with a tiny, fragile gland, or ball, of a sticky substance. The same thing occurs with tomato plants, and a tomato plant’s glandular hairs are really easy to see, if the light is just right. These glandular hairs, on whatever kind of plant bears them, are apparently useful in making it harder for would-be salad munchers (small insects) from getting too far into mischief on the plant, gumming up their little legs and mouth parts.

One last matter. Nearly all of the petunias you see for sale are hybrids, that is, the result of carefully controlled crosses between two different species. When botanists write down the name of such a hybrid, the letter “x” is generally placed after the first name, the genus, followed by the epithet name of the hybrid itself. When you see the name of such a hybrid in print, such as that for our Mystery Plant, you would say “The Petunia hybrid atkinsiana.”

[Answer: “Petunia,” Petunia x atkinsiana]

John Nelson is the retired curator of the Herbarium at the University of South Carolina, in the Department of Biological Sciences. As a public service, the Herbarium offers free plant identifications. For more information, visit or email

This content is being shared through the S.C. News Exchange and is for use in SCPA member publications. Please use appropriate bylines and credit lines.