I wonder why my roses have lost their fragrance. My ‘Double Delight’ roses used to have a good smell, and now the flowers are bigger and there is no fragrance.
It does seem mysterious that a once-fragrant rose should lose all fragrance. There are many factors which might cause the perceived lack of scent. According to The Graham Stuart Thomas Rose Book (Timber Press, 1994), rose scent itself is complex, and is composed mainly of geraniol along with many other substances. It is mainly released from tiny cells on the surface of the petals: “Scent is produced mainly in the petals and is given forth when the growth of the flower and the atmospheric conditions are right. From this it will be seen why double roses have more volume of scent than singles […] scent is especially apparent in most flowers when the air is neither too cold nor too hot […] In extreme conditions, such as wilting, extra scent may be released […] Usually the best fragrance is obtained from a newly opened flower growing on a healthy, well-established plant on a windless day when growth is exuberant […] we may expect fragrance to be at its best on a day when the air is warm and moist rather than dry, when the plant will be functioning well. It is not that moist air conveys better than dry, but that the plant is giving it forth in greatest quantity.”
From the above, you may want to consider the following
- When you discovered the rose had no scent, were the atmospheric conditions optimal for the release of scent?
- If scent is most prominent on healthy plants, are there any underlying reasons (pests, diseases, cultural problems such as overwatering, poor soil, etc.) the plant might not be at its strongest?
Other things to consider:
Environmental pollutants affect not only our sense of smell, but the fragrance emitted by flowers, as this 2008 University of Virginia study describes:
“‘The scent molecules produced by flowers in a less polluted environment, such as in the 1800s, could travel for roughly 1,000 to 1,200 meters; but in today’s polluted environment downwind of major cities, they may travel only 200 to 300 meters,’ said Jose D. Fuentes, a professor of environmental sciences at the University of Virginia and a co-author of the study. ‘This makes it increasingly difficult for pollinators to locate the flowers.’
The result, potentially, is a vicious cycle where pollinators struggle to find enough food to sustain their populations, and populations of flowering plants, in turn, do not get pollinated sufficiently to proliferate and diversify.”
Another thing that you might ask is whether your rose was grafted, and perhaps you are getting a different rose coming up from the graft. The loss of fragrance and the different appearance of the flowers makes me wonder if this could be what is happening.