Other than parentage and breeding there are many interesting things that affect the fragrance of roses.
Certain physical characteristics of a rose are indicators of fragrance, or is it that fragrance is created by certain physical characteristics? Certain genes produce certain chemical enzymes that create fragrance. Petals seem to be a primary source of the fragrance compounds. Later stages of petal development, when cells are rapidly expanding, releases greater fragrance. There has been a lot of studies trying to figure out all the science behind fragrance. They seem to have determined there is a direct correlation between petal color and fragrance, but there does not really seem to be an understanding of the why and how, at least not that I understand, as scent production is terribly complex.
Color and petal count are strong indicators of fragrance.
- Since fragrance is released by glands in the petals, roses with more petals often produce the most fragrance.
- Petals that are thick often produce more fragrance.
- Not all petals hold their fragrance when dry, these are not desirable for potpourri.
- Dark colored roses are most fragrant as they tend to produce more of the scent oils considered typical of sweet roses.
- Red and pink roses also tend to produce what we consider typical rose scent.
- Oils produced by yellow and orange rose petals are reminiscent of citrus
- Orange petals may often produce a fruity or clove scent.
- White and yellow petals often produce a lemony or nasturtium scent.
Aside from color, there are several factors that affect, and change, the degree of fragrance from roses. For example, fragrance oils evaporate at different rates, so the fragrance level can change over a period of time. Environmental factors can change fragrance levels but not necessarily predictably. Sometimes it is simply the change of weather conditions that triggers fragrance release.
- Warm sunny days tend to intensify fragrance
- Fragrance is typically most intense in cool early morning before the oils start evaporating
- The first blooms of the season are generally the most fragrant
- A half opened bloom is ready for pollination and so is releasing intense scent to attract pollinators
- Heat and humidity may enhance fragrance
- Moist soil can enhance fragrance
- Drought may reduce fragrance
- Temperature extremes, both heat and cold mayl reduce fragrance.
- Cutting a rose may intensify fragrance, a nice bonus when you cut roses for a vase
- Mildew reduces or causes loss of scent.
It is fun and interesting to monitor changes that influence fragrance, but even better is the pure enjoyment of a fragrant rose garden.