It is the wild (species) roses - fertile and having the simplest of forms - which are largely unscented. And it is roses with complex shapes, and many petals, which are likely to have a scent. Hybrid Tea (bred from the Tea roses of south China and Hybrid Perpetuals) are very likely to be scented - as are old-fashioned roses such as Damasks, Gallicas, Albas and Bourbons.
The scent of a rose is thought to arise from the base of its petals and the rose is optimally scented only when its bloom is wide open and the air surrounding it is warm. A rose is said to be at its most fragrant when its female reproductive parts (stigma, style, and ovary) are ripe and ready for a pollen-bearing bee to fertilize it. For the purpose of scent - and colour - is to attract a pollinator. However, the highly-bred Hybrid Teas (for instance) are not very fertile and, while their pistils may ripen, these roses tend not to form hips and set seed. |
The scent itself - the attar of roses - comes principally from the molecules of plant oil: Rhodinol, Citronnelol, Geraniol and Nerol. 'Attar' is the Persian word for 'fragrant' and attar is more valuable than gold.
It is the old-fashioned Damask roses (thought to originate from Iraq in the medieval period) - and flowering only once in the season - that are harvested for their petals and their attar. And it is these roses which epitomize the fragrance of a rose. |