Pelargoniums: An Herb Society of America Guide
Other Uses
Insect Repellent
Despite the fact that the plant sold in the 1990s as "citrosa mosquito-fighter" was a hoax (see History & Folklore section), there are pelargoniums with documented insect repellent activity. In a study published in 2003 in Bioresource Technology, the leaf extract of a plant identified as Pelargonium citrosa (not an accepted taxonomic name) deterred the malaria-transmitting mosquito Anopheles stephensi (42). Dr. Arthur O. Tucker points out, however, that this study did not assess the whole plant or essential oil but a methanol extract of the plant that would have selectively extracted constituents of the essential oil and other classes of compounds (89). It may have even extracted any insecticides that had been sprayed on the plant (89). Alcohol extract of Pelargonium reniforme leaf also reportedly repels mosquitoes and provided 63.3% protection from Anopheles arabiensis for 3 hours in a test involving 3 human subjects (36).
Indole alkaloids in some zonal pelargoniums are reported to repel whiteflies (40, 100). Wild
geranium extracts (Pelargonium sp.) repel the cockroach Blatella
germanica, and rose geranium extracts allegedly repel the flies Musca domestica and
Culex fatigans (79). The dried leaves of P. radens are used in insect-repellent sachets (14), and some of the scenteds (species
unidentified) are planted as intercrops to prevent insect infestation (29).
Preservative
Some Pelargonium essential oils have potential as food and cosmetic preservatives.
Pelargonium oil has demonstrated antibacterial and antifungal activity against a variety of bacteria and
fungi. Of bacteria, greatest effect was found for gram positive species (26). Oil of an
unidentified Pelargonium species was effective in inhibiting the growth of
Yersinia
enterocolitica and the dairy products organism Brevibacterium linens, but it encouraged the
growth of E. coli and Klebsiella pneumoniae (26). Pelargoniums including the cultivars
P. 'Attar of Roses,' P. 'Sweet Mimosa' and P. 'Paton's Unique' have demonstrated antimicrobial activity
against Zygosaccharomyces bailii, Salmonella enteriditis and Listeria innocua in a model food
system of quiche filling (56). In a separate study, essential oils of 'Sweet Mimosa'
(P. 'Sweet Miriam'), P. 'Mabel Grey,' P. graveolens,
P. 'Atomic Snowflake,' P. 'Royal Oak,' 'Attar of Roses,'
P. 'Chocolate Peppermint' and P. 'Clorinda' inhibited the growth of
Staphlococcus aureus in a model food system of broccoli soup (51). According to the authors of this 2003 study,
Pelargonium essential oils "show potential against some micro-organisms, but only in some food
systems" (51).
Tobacco Substitute
In South Africa, the leaves of P. papilionaceum are smoked and used as a tobacco substitute (68, 95).
Nanotechnology
Believe it or not, pelargoniums even play a role in nanotechnology. Proteins and enzymes from Pelargonium graveolens leaf extract have been used to synthesize silver and gold nanoparticles (76, 77). Silver nanoparticles have also been synthesized using bacteria and fungi, but reduction of silver ions occurs more quickly with P. graveolens (77).
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