The rose of florists is a heavily engineered object and bears limited resemblance to the plant the classical world knew.
Rosa is a genus of roughly 150 species of prickly shrubs in the Rosaceae, the family that also contains apples, pears, plums, cherries, almonds, strawberries and hawthorn. The wild rose has five petals. The many-petalled bloom is the result of a mutation converting stamens into petals, selected for and multiplied by cultivation; a fully double rose is a partially sterile flower.
The prickles are not thorns in the botanical sense. A thorn is a modified shoot and a spine a modified leaf; a rose's are prickles, outgrowths of the epidermis, which is why they snap off cleanly without tearing the wood.
The fruit is the hip, a fleshy receptacle enclosing the true fruits. Rose hips are unusually high in vitamin C, and this is not folklore: rose hip syrup was collected and distributed as a national programme in wartime Britain when citrus imports failed, and the scheme is documented in government records.
The scent chemistry is genuinely complex: hundreds of volatiles, dominated by compounds including geraniol, citronellol and the rose oxides, plus beta-damascenone, which is present in vanishingly small amounts and contributes disproportionately. Attar of roses requires an enormous mass of petals for a small yield, which is why it has always been expensive, and the main production centres are the Bulgarian Rose Valley and Isparta in Turkey. Most rose scent sold is synthetic, and most modern florist roses have had their scent bred out in favour of vase life.