Sometimes plants hitch a ride with others, so keep your eyes open! Ill.: www.pikpng.com & www.vhv.rs, montage: laidbackgardener.blog
I don’t know about you, but when I go plant shopping (and, to be honest, it’s about the only kind of shopping I enjoy … well, except for buying gardening books!), I’m always on the lookout for bonus plants. That’s what I call those extra plants you sometimes find in a pot.
Now, most often these are just another copy of the original plant. Say, in a row of echinaceas or delphiniums, most with just one plant in the center of the pot, every now and then there is a pot with two plants! I can see other gardeners mostly choosing the ones in bloom, but blooming plants generally tend to get broken when they’re handled or planted and I usually pass them up. I prefer getting two somewhat smaller plants for the price of one. I figure I’ve just bought the plant half price!
Stowaway Plants
Bonus plants aren’t always just doubles of the original. Sometimes, something else is growing in the original pot, usually something much younger and clearly different from the original. A seedling of … who knows what? It could, of course, turn out to be a weed, but unless I recognize it as such, I really can’t resist trying. These are the ones I call stowaway plants.

I have gotten some duds that way, true enough, and once tenderly cared for a stinging nettle for quite a while before it stung me and I realized what it was. But I’ve also discovered some truly stupendous plants hitchhiking in other pots.
Ferns often seem to germinate in other pots and I’ve picked up some beauties that way.

And my all-time favorite geranium, Armenian cranesbill (Geranium psilostemon), a giant of a geranium that blooms right through the summer into fall with startling dark-eyed brilliant magenta flowers, first came to me as a stowaway. It took me years to find out what it was, as it is just not on offer in nurseries where I live. True, it does self-sow quite abundantly, but I just love it. With plants of it now growing here and there throughout my yard, it now pretty much defines my summer garden.
I’ve picked some charming phloxes, sweet Williams, columbines and bellflowers that way, and also my very first Joe-Pye weed (Eupatorium maculatum… I think!). And even baby trees and shrubs, not all of which I’ve been able to keep because of space restrictions. And I mustn’t forget houseplants: they often have some pretty exciting stowaways.
Plants Only

I should point out that I limit my choice of stowaways to plants. I also check plants for insects and if I find any stowaways in that category, unless I know it is something beneficial like a lacewing or a ladybug, the plant will remain in the store. In fact, if the bug is something truly horrifying, like mealybugs or scale insects, I’m very unlikely to buy anything in that outlet.
Bonus plants: just another thing about gardening that makes it so exciting!
We try to keep weeds out of our material, but some sneak in. A particular area of the nursery got seeded with poison oak that fell from high in an adjacent redwood tree. (I needed to cut the poison oak at the base.) For some small plants, we put two or three cuttings in each can; and I sort of wonder how many got separated when planted in their forever homes.
I got my first bonus plant this year! It came with my rosemary! I’ll snap a pic to share. Great information!