Thorns, Prickles, Spines and Bristles

Plants have several ways to grow armor to discourage animals from browsing on them.

A thorn is a sharp, pointed, modified branch or stem. It can be at the end of a stem, or be its own short pointed woody branchlet.

Buffalo Berry – photo courtesy Steve Matson

A prickle is an outgrowth from the skin of the stem. It’s a kind of stiff, sharp hair that grows from the epidermis.

Himalayan Blackberry – photo courtesy Zoya Akulova-Barlow

A spine is a hard, sharp, pulled-together leaf or flower part. They’re often found at leaf margins. Sometimes the whole leaf becomes a spine, such as with Cactus.

Arizona Thistle – photo © Frank Rose, Desert Museum

A bristle is a dry, colorless, stiff hair. In leaves, bristles are an extension of a leaf vein that goes beyond the margin.

Black Oak – illustration © John Muir Laws

In dandelion pappus, bristles are appendages to the fruit, creating a parachute to fly away on.

In fact, the term bristles, as with hairs, is more about the look of an appendage rather than its structure. Stems and flower parts have a wide variety of them.

Want more? See Wikipedia.

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