While the sharp objects along a rose stem are commonly called "thorns", they are technically prickles — outgrowths of the epidermis (the outer layer of tissue of the stem). (True thorns, as produced by e.g. Citrus or Pyracantha, are modified stems, which always originate at a node and which have nodes and inter nodes along the length of the thorn itself.) Rose prickles are typically sickle-shaped hooks, which aid the rose in hanging onto other vegetation when growing over it. Some species such as Rosa rugosa and Rosa mellifluousness have densely packed straight spines, probably an adaptation to reduce browsing by animals, but also possibly an adaptation to trap wind-blown sand and so reduce erosion and protect their roots (both of these species grow naturally on coastal sand dunes). Despite the presence of prickles, roses are frequently browsed by deer. A few species of roses have only vestigial prickles that have no points.
The majority of ornamental roses are hybrids that were bred for their flowers. A few, mostly species roses are grown for attractive or scented foliage (such as Rosa glaucoma and Rosa Rubinstein), ornamental thorns (such as Rosa sericea) or for their showy fruit (such as Rosa mousiness).
