Increasing Geranium EO Yield

A South African study published in HortScience suggests that essential oil yield in Rose-scented Geranium (Pelargonium capitatum x P. radens) is increased by frequent irrigation and brief water stress before harvest. (h/t Herb Companion.)

The experiment was conducted on geraniums growing in pots, using varying irrigation frequencies. From the abstract:

Both herbage yield and essential oil yield positively responded to frequent irrigation. Thus, higher herbage and essential oil yields were obtained from the highest irrigation frequency.

A one week stress period of withholding irrigation just before harvest was found to significantly increase total essential oil content as well as oil content per fresh herbage weight. Interestingly, the stress period modified the chemical content:

Citronellol and citronellyl formate tended to increase with an increase in the stress level, but the reverse was true for geraniol and geranyl formate. Other major essential oil components were unaffected by water stress.

Published in HortScience 43: 286-583 (2008)

For more information on the cultivation of Rose Geranium, visit the BioAfrica Plant Profile.

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