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Dr. Leda's Rose Journal |
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Get Your Olfactory Rebate
By Dr. Leda Horticulture, O. R.
October 2003
Readers ask Dr. Leda some nosy questions....
Dear Dr. Leda:
I grow roses strictly for their fragrance. I'm not interested in any rose that doesn't smell good. My problem is that so many otherwise nice roses don't have much scent. Why do they even bother to make roses that aren't fragrant?
—Grumpy in Greenwich
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In late October, subscribers to Dr. Leda's Journal get an advance peek at our 2003-2004 catalog AND advance ordering. Subscribe today to get your members-only notice! You can browse the site now, and watch your email for the new 2004 catalog later this month.
Dear Grump:
Ah, the allure of fragrance! Such a subtle, bewitching, ephemeral quality. Legend has it that when asked what she wore to bed at night, Marilyn Monroe answered, "A dab of Chanel No. 5." No doubt this tantalizing reply caused many a pulse to pitter-patter in its day. But let's be frank: would that same dab of perfume have been as seductive had it adorned a less desirable package of assets?
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| 'Double Delight,' a highly fragrant Hybrid Tea rose. |
Perhaps it would have. As the billion dollar perfume industry has cleverly deduced, our sense of smell has a powerful ability to trigger vivid fantasies, emotions, and memories. And yet! So much more is required of a successful sex goddess--and a successful rose--than just an appealing fragrance.
Faced with a limited amount of genetic material, rose hybridizers are constantly forced to select one favorable trait over another. All too often, fragrance must take a backseat to such indispensable features as color, form, disease resistance, remontance, and the flower's ability to hold on to its petals for more than thirty seconds.
But don't despair! Thanks to recent scientific advances, this trend may soon reverse. Using detailed gas chromatography and mass spectometry analyses, researchers have identified more than 4,000 aromatic components from rose petal extracts. These volatile molecules, which include oils, resins, alcohols, fatty acids, hydrocarbons, sesquiterpenes, and other unattractively named compounds, are combined and emitted by the rose to produce its signature fragrance. Recent advances in gene mapping techniques are enabling scientists to correlate each of these substances with one or more fragrance-producing genes in a rose's DNA. Armed with this information, rose breeders will someday be able to encode optimal fragrance production into each and every rose's genetic makeup.
Until that day arrives, enjoy the fragrance in the roses that are already blessed with it. But don't overlook the other sensuous, hedonistic pleasures a rose has to offer. If all you notice about roses--or sex symbols--is their perfume, then you're missing some of the finest enticements life has to offer.
Dear Dr. Leda:
Last spring I planted the pink hybrid tea 'Frederic Mistral' in my garden. At first, it was wonderfully fragrant, but as the summer wore on the fragrance seemed to disappear. What went wrong? Is there anything I can do to bring it back?
—Disappointed in Dallas
Dear Dis:
You have excellent taste is roses! 'Frederic Mistral,' one my very favorites, is beautiful, healthy, and an abundant bloom machine. But I have the same problem here in Louisiana: it smells fabulous in spring and fall, then the fragrance dwindles during the sweltering inferno we so euphemistically call summer.
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| 'Frederic Mistral' about to open. |
The strength of a rose's fragrance on any given day depends on the temperature, the amount of humidity, the time of day, and the age of the bloom. These factors will determine how many volatile fragrance molecules a rose produces and emits, as well as how far and how fast those molecules can travel through the atmosphere in their intrepid pursuit of your nostrils.
Drought, high humidity, extreme heat, and very cool temperatures can all diminish the fragrance of a rose. While ample moisture facilitates the release and movement of aromatic compounds, excessive atmospheric humidity (hello, Louisiana!) overpowers them. If the air is too cold, the volatile oils may not be converted to a gaseous state. But if the air is too hot (hello, Dallas!), the volatiles will evaporate so quickly you won't even notice them. Each rose has its own finicky set of ideal conditions.
So, what can you do to resuscitate Freddie's flagging fragrance, other than move to Seattle or pray for a cataclysmic shift in the global climate? You can make sure the roots never dry out, and that the soil doesn't deviate from its preferred pH (6.5 - 7.0). These are the sorts of manmade calamities that hinder fragrance production.
Also, be mindful of timing. Because of their volatile nature, the fragrance molecules are most highly concentrated on the first day the flower opens; after that, they begin to drift aimlessly toward the stratosphere. So visiting (and cutting) a rose early in its development will give you a more generous sample of scent.
Dear Dr. Leda:
I recently cut a bouquet of the old Noisette rose 'Jaune Desprez,' which to me has very little fragrance. But my husband insists it's the sweetest thing he ever smelled. Which of us is hallucinating?
—Puzzled in Palo Alto
Dear Puzz:
You're both right. As Abe Lincoln might have said if he'd been a rosarian instead of a lawyer, "A rose will smell good to some of the people all of the time, but not to some of the people any of the time." In other words, there are some people who just can't smell certain roses. And as much as I love my 'Jaune Desprez,' I, like you, am unable to detect its legendary fragrance.
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| 'Jaune Desprez,' a healthy Noisette climber. |
This isn't surprising when you consider how complex the olfactory process is. First, those ephemeral fragrance molecules must be inhaled onto the olfactory neurons, which are hidden way up under the roofs of our dark, unknowable nasal caverns. And once they arrive, they may or may not trigger messages that the brain can translate as the heavenly scent of a rose.
To some extent our ability to smell is genetically programmed at birth. We all have slightly different genes, including the genes that decide which of our smell receptors will bind like puzzle pieces to certain fragrance molecules and not others. For reasons that Mr. Darwin never attempted to explain, some humans seem to come equipped with the ability to smell 'Jaune Desprez' while others must stumble through life without it.
Our sense of smell also tends to diminish with time. Olfactory function is highest in childhood, plateaus from the teens through the 50s, and drops starting at about 60 for women, 65 for men. Other causes of olfactory loss may be upper respiratory infections, smoking, or a sharp blow to the head.
I've learned to work around my olfactory limitations by mixing a few roses that I can smell into every bouquet, and by cultivating an overblown obsession with color and remontance. Also I remind myself: there are some people who can hear their roses talking. I myself seem to lack this ability, and yet my life is rich and meaningful without it. Play the cards you're dealt, and enjoy your roses!
