Researchers in South Africa have found a way to produce more oil. Unfortunately, it’s not the kind you put in your car–it’s the fragrant essential oil of rose-scented geranium (Pelargonium capitatum ×P. radens).
This is good news not only for commercial producers of essential oil, but also for home herb growers who want to maximize the fragrance of their scented geraniums’ leaves for drying.
The secret in a nutshell? Water wisely: Water plants thoroughly and often when they are growing, then withhold water for one week before harvesting leaves for drying. In the study, rose-scented geranium plants were planted in plastic pots and grown in either a greenhouse or quonset house (plastic-covered hoophouse). After the plants grew for six months, they were divided into groups and given different watering regimens.
The scented geraniums produced more foliage the more often they were watered. The group that was watered daily, and then given a one-week dry period before leaf harvest, produced significantly more essential oil. In the case of rose-scented geraniums, a lot followed by a little goes a long way.
For more information, see HortScience 43(2):500-504, 2008.
Robin Siktberg is horticulturist and editor for the Herb Society of America (www.HerbSociety.org).