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* Thorns: Spiky stems

Thorns are defined as modified shoots. What does that mean? Basically, it’s a branch that has crossed over to the dark side. Thorns are made from the stuff of stems!

According to Missouri Botanical Garden’s Grammatical Dictionary of Botanical Latin, a thorn is defined as “a short, rigid process of a plant, developed from a bud typical of a leafy branch.” Many hawthorns (Crataegus spp.), as well as honey locust (Gleditsia triacanthos), are examples of commonly found plants in Ohio that possess thorns. As the definition implies, thorns occur in the axil of a leaf where a branch would normally grow, but instead, conclude in a sharp, durable, woody point. As such, they contain internal vascular tissue (phloem and xylem) that the rest of the plant’s branches possess.

* Spines: “Leaf” us alone

Rather than being made from the stuff of stems, spines are modified leaves or parts of leaves. Sometimes, spines occur in pairs, as is the case with barberry. The Grammatical Dictionary of Botanical Latin defines a spine as “a stiff, sharp pointed protective outgrowth or plant process, as a modified leaf, leaf part, petiole or stipule.” Cacti (family Cactaceae) and some holly species such as American holly (Ilex opaca) and English holly (Ilex aquifolium) are armed with spines. (Interestingly, many holly species lack this defense mechanism, including winterberry, Ilex verticillate, and Ilex paraguariensis, the plant that makes up yerba mate.)

The most vicious spines I have personally encountered stemmed from a leguminous tree species called Prosopis kuntzei (referred to as Neltuma kuntzei in some literature). Inhabiting the Gran Chaco of Argentina, Bolivia, and Paraguay, arguably one of the harshest environments in the world to be a plant, this tree seems to be a worthy opponent with a canopy of innumerable, long spines that can extend past a foot in length. Though it does form some leaves in the spring, they quickly fall off and allow the spines to be the principal photosynthesizers. Fortuitously, I was able to come out alive on the other end.

And since spines are formed from a plant’s leaf tissue, they also contain internal vascular tissue.

* Prickles: Sharp skin tags

Though prickles can definitely pack a punch in terms of pain (as every rose gardener and florist will surely tell you), they differ from thorns and spines in the fact that they are derived from a plant’s skin tissue, thus do not contain phloem and xylem. Prickles tend to be short and sharp and (if you dare) easier to break off. According to the Oxford English Dictionary, a prickle is “a rigid, but comparatively short and slender, sharp-pointed outgrowth that is an extension of the epidermis of a plant.”

Roses (Rosa spp.), many brambles (Rubus spp.), greenbriers (Smilex spp.), and Aralia spinosa, the fierce Devil’s walkingstick, (if that common name isn’t a warning not to touch with bare hands then I don’t know what is) are all plants that possess prickles.

“Every rose has its thorn

Just like every night has its dawn

Just like every cowboy sings his sad, sad song

Every rose has its thorn

Yeah it does…”

Sorry, Bret Michaels. Turns out it doesn’t. Roses have prickles.

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Carri is the ANR Extension Educator for The Ohio State University in Morrow County. She specializes in horticulture, forages, and livestock.