Take A Deep Breath – What Makes Tree Scents?

Why do pine trees (genus Pinus) smell the way they do? What gives sassafras (genus Sassafras) its distinctive, sweet and spicy scent? What makes a whiff of eucalyptus (genus Eucalyptus) so fresh and invigorating? The source may be the same: terpenes (and terpenoids, chemically modified terpenes). Varieties of plants as well as some insects produce these organic compounds, many of which carry strong odors. Odoriferous leaves, bark, and even roots are often rich in terpenes and terpenoids. Though some scents work to attract pollinators, others are defensive, meant to deter pests and attract pests’ predators. Eucalyptus, sage, and mint are a few examples of defensively-scented terpenoid producers. Terpene production increases dramatically in heat, suggesting that terpenes play a role in temperature regulation in forests.

More than a treat for our noses, many of the terpenes and terpenoids emitted by conifers have been shown to be good for our health. In Japan, the Forest Agency encourages a practice called “forest bathing” (shinrin-yoku), which is, essentially, breathing while taking meandering, meditative walks through the forest. The Agency recommends forest bathing as a stress-reliever and mood-booster. There’s more to the forest’s restorative benefits than the calming serenity of nature. The terpenes and terpenoids produced by conifers — which make up much of the forests in Japan — have anti-inflammatory, antioxidant, analgesic, and even anti-tumor properties, as demonstrated in a study published earlier this year.

Essential oils used in medicine and aromatherapy are largely composed of terpenes and terpenoids. Pine trees, smelly trees well-beloved for their scent, produce pinene, a terpene shown to have anti-inflammatory effects. The peppery, minty scent of phellandrene and eucalyptol, both emitted by eucalyptus trees, are antidepressive as well as effective cough suppressants. Sassafras smells so sweet in part thanks to geranyl acetate, a fruity-, sweet-smelling monoterpene with antimicrobial properties.

Trees aren’t the only plants that emit terpenes. Limonene, found in citrus fruits, is used in cleaning products, cosmetics, and insecticides, and can relieve gastrointestinal issues and heartburn. Myrcene is a terpene found in a variety of plants, such as hops, mango, thyme, and cardamom, among others. Found in many flowers and spice plants (such as lavender and bay leaf), linalool is widely used in shampoos, soaps, and other scented hygiene products. Lavender oil is well-known for its calming qualities as well.

So — should you find yourself needing a respite from impending holiday frenzy, find a forest and take a bath.  We offer free Atlanta BeltLine Arboretum tours most Fridays and Saturdays, as well as specialty urban forest tours on a regular basis. Check our calendar for the the complete schedule!

Can’t escape to the woods? Poke your nose in the nearest pine tree and breathe those terpenes in. Then, go about your business, a little calmer, a little refreshed.