Just saying the word "rose" conjures up images of romance, secret admirers, Valentines gifts, and bridal bouquets. Romantics imagine soft, red petals and long, graceful stems, but practical gardeners know all about painful, pointy thorns. As the saying goes, every rose has its thorn. But, what we call thorns are actually not thorns at all.
Thorns, like those found on the Hawthorn tree, are modified branches that project from the stem and branches of a woody plant.
They are very sharp and quite strong because they are made of the same stuff as the stem of the tree or bush. Thorns are deeply embedded in the woody structure of the plant and can‘t be broken off easily. Those nasty points on the stem of the rose are not true thorns: they are what scientists call "prickles."
Prickles are smaller than thorns: they are sharp outgrowths of the plant‘s outer layers, the skin-like epidermis, and the sub-epidermal layer just beneath it. Unlike a thorn, a prickle can be easily broken off the plant because it is really a feature of the outer layers rather than part of the wood, like a thorn.
Both prickles and thorns protect the plant from predators, and, maybe, from lovers looking for a free bouquet. But perhaps we call the rose prickles "thorns" because saying "every rose has its prickle" doesn‘t seem to do justice to the pain of unrequited love.