Thorn (botany)

Thorns are branches or stems that are modified into hard structures with sharp, pointy ends. Though thorns are similar in appearance to spines or prickles, the three structures are differentiated by the plant organ from which they arise: thorns are modified stems, spines are modified leaves, and prickles are extensions of the cortex and epidermis. Many plants commonly thought of as having thorns actually have spines or prickles. Roses, for instance, have prickles.

Like spines and prickles, thorns are generally used by plants to protect themselves from herbivores.