This is a good news/not so good news post. First the good news. Turns out, in the search to find powerful yet natural mosquito repellents, we need but look at one of our very own native grasses – specifically, sweet grass Hierochloe odorata. It also goes by the common but very auspicious names Holy grass, Manna grass, Mary’s grass, Peace grass, Unity grass or Vanilla grass. In north America, Hierochloe odorata occurs in southern Canada, northern Great Plains/Rocky Mountains and northwest of U.S., and New England. Not to be confused with the sweet grass Muhlenbergia filipes found in the southeastern United States.
Long used by Native Americans to deter mosquitoes, it is a sacred plant, used in peace and healing rituals. Leaves are dried and made into braids and burned as vanilla-scented incense; long leaves of sterile shoots are used by Native Americans in making baskets. The plant is showing great promise in scientific research. In laboratory tests, two sweet grass compounds drove mosquitoes away just as well as the widely-used repellent Deet. Imagine that!
One of the compounds is coumarin. Not only effective but it smells good too. Same stuff that renders Skin So Soft ( Avon’s moisturizer) as an anti-mosquito salve. The product is not advertised as such but users have long known it’s additional property. Coumarin is also a safe chemical.
Smells fine, safe to use, fends of mosquitoes – hmmm, what’s the problem then? Studies are still required to see how long the effects last. Oddly enough, coumarin is not registered or marketed as a repellent.
The second compound isolated from sweet grass is phytol. A common constituent in essential oils from plants. Phytol, similarly, is known to repel insects but is not currently sold for that purpose. Go figure.
And therein lies the not so good news. It’ll be at least two to three years before all of the research is completed to establish the efficacy, Still, I’m optimistic. I dream of summer evenings spent in the garden sans the swatting and scratching.
In the meantime, I’m seriously planning to introduce sweet grass in the garden. Hierochloe odorata is a very hardy perennial, able to grow to the Arctic Circle. Its leaves do not have rigid stems, so only grow to about 20 cm (7.9 in) in height, and then the leaves grow outward horizontally to 100 cm (39 in) long or more, by late summer. Grown in sun or partial shade, they do not like drought. Seeds are usually not viable, or if they are viable, take two to three years to develop a robust root system. So I’m guessing they will not be invasive.
I think testing out this plant near outdoor dining areas, swimming pools, children’s play areas and other spaces where humans gather, will be worth trying. I understand that the grass’ mosquito fighting property is more potent when it is dried so wearing a crown and garland of braided sweet grass might well become my go to accessories for outdoor soirées. At least until coumarin is available as a commercial product. I will check if my local nursery carries the plant or will get me some. Stay tuned!
If any of you have knowledge or experience with sweet grass, please share!
(c) 2015 Shobha Vanchiswar