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California poppies

The forests’ of the West have remarkable, yet individual, scents. Different parts of different plants emit different smells.

If a flower produces an odor, it’s usually to attract pollinators. Fragrant flowers attract bees and butterflies. Rancid flowers, which mimic the smell of carrion and feces, depend on flies and beetles to cross-pollinate. Pacific northwest skunk cabbage is a good example of a fetid smelling flower.

Some odors, on the other hand, may be protective and part of the mechanisms that plants use to discourage herbivory. And some plants produce toxic chemicals but do not produce odors – animals learn quickly to avoid these plants.

Most of the odiferous plant compounds found in flowers are so-called essential oils. They are made up of complex compounds and once released into the air they quickly evaporate.

There are about 20 different chemical groupings which make up essential oils. Those of spruce, pine and firs belong to the terpenes. The paint remover turpentine comes from terpenes. The oranges and yellows of flowers, fruits and leaves also belong to terpenes. As does latex or natural rubber, which comes from the South American rubber tree.

Certain plant parts produce scents which tree scientists do not fully understand. For example, on a hot summer afternoon, ponderosa pine bark has a mellifluous butterscotch smell. The exact reason is not known.

Balsam poplar and black cottonwood produce a sweat honey-like smell that comes from their buds. As buds break and leaves unfurl, they are coated with a potent natural insecticide. It is no wonder that the bees collect this sticky bud substance and use it as a sealant on their hives to prevent ants from intruding. Nor should it be surprising that the poplar buds contain efficacious antiseptic properties that are excellent in fighting throat infections.

Plant fragrances and essential oils have, in fact, been exploited by humans since the time of the Egyptians. They used concoctions of tree tars, cinnamon, wood chips and cloves, among other things, to wrap and preserve dead bodies.

The Egyptians also pioneered perfume and its development more than five millennia ago. Italy and France incorporated some of this essential plant technology thousands of years later and today continued the lucrative plant based tradition of making perfume.

The most costly of pure essential plant oils is the attar of roses, produced in the Valley of Roses near Sophia, Bulgaria. Not only is it highly soothing for the central nervous system but it is an effective natural antidepressant.

Eucalyptus essential oil has medicinal properties and is known to ward off air-borne viruses. When I travel, which I do a lot, I always place a couple drops on my hands, rub them together, and take two or three deep breathes of this strong-smelling natural tonic.

Essential oils are used in many household products from solvents, detergents, insecticides, furniture polishes, paints, paper and inkjets to pet foods.

The forests’ of the West contain an unlimited supply of goods for which scientists are just beginning to discover many different uses. When next in the forest, take a deep breath and try and decipher the array of different fragrances that you encounter.

Dr Reese Halter is a conservation biologist at Cal Lutheran, public speaker and founder of the international conservation institute Global Forest Science. His most recent book is The Incomparable Honeybee and the Economics of Pollination Contact him through

See Dr Reese in Desert Wildflowers


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