Herbal plants could help one another to flourish, according to an evaluation by horticulturists at South Verona's Mississippi State University. Yields of essential oils from peppermint were increased after spraying them with distillates of aromatic herbs, such as sage, rosemary and thyme. And with such aromatic essences a common by-product of steam distillation of such herbs, finding a beneficial use for these waste-waters will help to reduce problems of discharge into streams and rivers.
Peppermint and spearmint are used widely, not just for their freshening flavor, in everything from gums to toothpaste, but also as remedies for a variety of digestive problems. Peppermint's active compounds have both antispasmodic and anti-inflammatory properties, and extracts of the herb are often prescribed for those suffering from irritable bowel syndrome (IBS).
For those growing the plant commercially, increasing the yields of essential oils is obviously going to be beneficial. The team at Mississippi State University, led by professor Valtcho D. Zheljazkov, believed that hormones extracted from sage, thyme, and rosemary had yield-enhancing potential from previous studies. ''We hypothesized that residual distillation water could have an effect on peppermint and spearmint plants when used as a foliar spray'', he said.
So the team sprayed both peppermint and spearmint crops with waste-water distillates, from 15 aromatic herbs, as well as sprays containing just isolated extracts of the plant hormones – methyl jasmonate, gibberellic acid, and salicylic acid. What they found was that salicylic acid boosted the growth of both peppermint and spearmint. Peppermint, in particular, responded well to the application of the hormones, as well as the waste-waters of 7 of the 15 plants tested – essential oil yields were significantly boosted.
The paper published in HortScience, house publication of the American Society for Horticultural Science, concludes more research needs to be done to find the best ways to reproduce these results for everyday field use. But it does offer the promising potential to complete the loop of a virtuous circle, with one herb giving another a helping hand and so helping to zero waste.