Fragrance – What Is It?

By: Mary Peterson, meg21@stny.rr.com , Horseheads, NY

“What’s in a name?
That which we call a rose
by any other name would smell as sweet.”
-William Shakespeare, Romeo and Juliet

To begin a discussion of fragrance there are a few basics that should be addressed. Whether or not you smell a particular fragrance in a rose depends in some measure on your own personal olfactory system and how sensitive it is.

The Eco-culture in which you grow your roses is also responsible in a large degree to the amount of fragrance produced by the roses. There are also some additional factors regarding fragrance that should be taken into account.

The amount of sunshine, duration and intensity is an important factor. Temperature, humidity and wind conditions also affect the development of scent. Another aspect to fragrance is that it is affected by disease. Mildew will cause a loss of scent in roses.

Whether a rose produces a fragrance is due in large part to its genetic ability to produce fragrance. Fragrance is produced by certain glands on petals or leaves. Chemically speaking, we identify certain fragrances produced by aromatic alcohol, aldehyde, fatty acids, phenol, carbonic acid, essential oils and resins.

Since the gene for fragrance is recessive, unless both parents have the gene, you may find the offspring to be only slightly fragrant or have no fragrance at all. A cross of two fragrant varieties could be expected to produce a preponderance of fragrant seedlings; possibly all of them would be unless the two parents were chosen with widely different types of fragrance.

The ingredients of perfume are found in the chloroplasts. They are surrounded with glucose which causes them to create the scentless glucosides which are stored or carried in the petals. The scent becomes noticeable if the glucoside is hydrolyzed by an enzyme. The production of a floral scent is a very complex chemical reaction that is influenced by various external influences.

The chemistry of rose fragrance is a complicated mixture of essentials oils. Most important is Rhodinol which has the fragrance of ‘old roses’. Another familiar scent is geranium that is produced by Geraniol. Nerol brings the fragrance of magnolias. In orange and yellow roses, Eugenol imparts a spicy fragrance often found in oil of cloves.

Quite possibly the most important factor next to sunshine, soil, and water pH is the amount of moisture available to the plant. When the soil is moist, the roses smell their sweetest because the scent ingredient in the chloroplast increases proportionately and is conveyed to the petals in larger quantities.

As early as the 13th century, rosarians have been intrigued by the possibility of breeding fragrance into their roses. As a rule, darker colored roses are more likely to be highly scented than those of lighter shade. The exception is when a flower has more petals; the more petals available – the stronger the scent is likely to be. Heavy petals with a velvety sheen are also more fragrant. The scent comes from tiny cells on the underside of the petals you can see with the aid of a microscope.

Not surprisingly there is a definite connection between color and scent. Red and pink roses tend to give off the typical rose scent while the scent from yellow and white roses often is identified as orris, nasturtium, violet or lemon. Orange shades are frequently associated with the odor of fruit. On overcast days, scent is reduced and when the weather is both cold and overcast, it is usually hard to detect any fragrance at all.

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