Shade Effects on Leaf Production and Essential Oil Content and Composition of the Novel Herb Eucalyptus citriodora Hook.

The influence of light conditions on plant growth and essential oil production of the novel herb Eucalyptus citriodora (Lemon-Scented Gum) was investigated. Pot-grown plants were grown either directly exposed to sunlight or 'shaded' with the least exposure to sunlight (75 % shade) or with intermediate exposure to sunlight (50 % shade). Shaded plants were generally taller, had thicker stems and wider canopies, grew more branches, produced larger leaves, produced more essential oils per plant, produced similar concentrations of the major essential oil components (citronellal, beta-citronellol and trans-caryophyllene) in the leaves and produced record high concentrations of (+/-)-p-menthane-3,8-diol, a component having superior insect repellent properties, than the ones grown under full sun. Plants grown under '50% shade' were likely to be the most productive of leaves and essential oils, either for personal use in tea infusions or for production of leaf-essential oils, potentially having improved capacity for insect repellency.