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The Basis of Scents

WHY DO ROSE GERANIUMS SMELL LIKE THAT?

By Wayne L. Handlos, Ph.D.

We have learned  that rose geraniums produce some essential oils that make them useful

for aromatherapy. The article "Trichomes"  contains information and images of  the hairs on the surface

of geranium plants. These hairs produce the essential oils that give the geraniums their distinctive odors.

But what are the chemical compounds that that are found in these essential oils?                                                                                                                                                                                                                                                                Rose scented Pelargonium

At the risk of going overboard biochemically, the primary constituents of the essential oils of

the rose scented geranium (Pelargonium cv Rosé) are listed in the table on the next page.

Many studies and analyses have been done on geraniums (as well as many other plants) to

identify the compounds that they contain. (These studies are done for a variety of scientific

reasons relating to the study of plant evolution, relationships between plants and insects,

search for new medicines and physiological agents, search for insect attractants and pesticides,

elucidating metabolic pathways, etc.) Because rose geranium oil is such an important

ingredient for the “scent industry” (it has many of the same characteristics and constituents

of rose oil and is much cheaper to produce) there are many studies available.

The composition of the oil varies depending on the country of origin, stage of growth, season,

nutrition of the plants and probably other factors.

Rose geranium oil from Egypt wholesales for $884 per gallon. Damask rose oil from Bulgaria

costs £37.11 for 10 ml (2 tsp) while Zambian rose oil is £51.30 for 10 ml. On the other

hand, geranium oil varies from £4.87 to £8.78 (for Bourbon oil from Reunion) for 10 ml.

                             COMPONENT             %                FRAGRANCE             PARTS IN SYNTHETIC GERANIUM  OIL

                             Linalool                        4.6             sweet, floral                                      1000

 Cis-rose oxide             0.2             fruity, rose, sweet                               150

 Menthone                     0.4             minty                                                     150

 Isomenthone                7.8             clean mint                                             500

    ^ geraniol           Citronellol                   19.0              floral, fresh, rosy                               2800

                             Geraniol                     21.5             sweet, rose-like                                1500

 Citronellyl formate       8.5             strong, fruity, rose-like                      1000

 Geranyl formate          9.5              fruity, floral, rose                                  800

 Beta-caryophyllene     0.8             cinnamon, clove, spicy                            ...

 Guaia-6-9-diene         7.2                       ......                                               500

   ^ citronellol          Geranyl propionate     1.6             floral, rose, lemon                               150

                             Germacrene D            2.1            woody, earthy, spicy                              ...

 Citronellyl butyrate     1.1             floral, fruity, rose                                    ...

 Geranyl butyrate         1.2             fruity, rose, apple                                  ...

 Phenylethyl tiglate      0.7            green, raspberry, strawberry, rose     ...

  ^ isomenthone       Geranyl tiglate             1.4            floral, geranium                                    150

 

© 2010, Central Coast Geranium Society (CCGS )