WHY DOTHOSE GERANIUMS SMELL LIKE THAT?
By Wayne Handlos, Ph.D.
In "Why Do Rose Geraniums Smell That Way" , I listed the primary components of ‘geranium oil’, basically the compounds
which give rose geraniums their rosy/floral fragrance. But what about all of those other scented leaf geraniums (Pelargonium)?
Numerous studies have been conducted to determine the components of the essential oils produced by
other species and cultivars of the scented Pelargoniums. These compounds and their fragrance characteristics
are listed in the accompanying table. This has led to another classification of the scented geraniums
by Lis-Balchin. Namely five categories are recognized by her: rose, mint, peppery-pungent, citrusy, and
camphoraceous-pungent based on the predominant chemical produced by each. The rose category is characterized by the predominance
of the chemicals listed last month and includes such species as P. capitatum, P. radens, P. graveolens and the cultivars ‘Attar of Roses’,
‘Rosé’ and ‘Rober’s Lemon Rose’.
The mint category produces scents dominated by menthone and isomenthone and includes P. tomentosum (peppermint geranium),
‘Chocolate Peppermint’, and ‘Lady Plymouth.’ The peppery-pungent group includes P. vitifolium, P. papilionaceum and P. ‘Filicifolium’. The
distinctive chemical in these plants is citronellic acid. The citrusy group is characterized by producing the lemon/lime/orange scented
compounds like citronellol, geranial and neral. The familiar species and cultivars in this group includeP. citronellum, P. crispum,
P. scabrum,‘Lemon Fancy’ and ‘Mabel Grey.’
The camphoraceous-pungent group is a mixed bag of species and cultivars producing such fragrant compounds
as alpha thujene, alpha pinene, alpha terpineol, methyl eugenol, fenchone and p-cymene. Species
and cultivars in this group include P. glutinosum, P. x fragrans, P. odoratissimum, P. exstipulatum, P. quercifolium,
‘Clorinda’, ‘Copthorne’, ‘Village Hill Oak’ and ‘Sweet Mimosa’.
Obviously, different scents are detected depending on the proportions of the various compounds produced
by the different plants and hybridization can bring together different combinations of fragrant
compounds. On top of this there are the variations mentioned last week relating to the influences of
stage of growth, cultural practices and the effects of soil and weather.
Essential oils and fragrance compounds not found in the rose scented geraniums
Compound Fragrance Found in %
α pinene turpentine P. capitatum 47
β pinene woody, pine, resinous P. quercifolium 19
geranial strong lemon P. citronellum 42
neral sweet lemon ‘Lemon Fancy’ 28
α phellandrene peppery, woody ‘Chocolate Mint’ 2-17
β phellandrene peppery, minty ‘Sweet Mimosa’ 5
citronellic acid grassy, smokey P. vitifolium 76-83
geranic acid weedy, musty, woody P. papilionaceum 5
methyl eugenol clove, spicy P. grossularioides 11
p-cymene turpentine, woody P. glutinosum 16-23
limonene orange citrus P. glutinosum 2.8-13
hexenyl butyrate buttery, fruity P. glutinosum 8-15
α thujene pungent, woody P. x fragrans 9
fenchone camphor, earthy, woody P. x fragrans 8
terpinen-4-ol nutmeg ‘Village Hill Oak’ 11
α terpineol floral, lilac P. quercifolium 30