It takes 150 pounds of lavender flowers to produce just one pound of lavender essential oil! Like all crops, the yield from season to season is impacted by a variety of factors, including weather (a hot, dry growing season yields more lavender than a rainy season), the amount of sun the plants receive in the weeks before the flowers are harvested, and the age of the plants. On average, an acre of lavender will yield about 12 pounds of oil, although in a good year, it could climb to about 20 pounds.
The first step in the manufacture of lavender essential oil is harvesting the flowers. They're picked when the blooms are fully developed -- when the oil in the flowers is at its peak and contains the maximum amount of esters, or fragrance compounds. The flowers are then steam-distilled to extract the essential oils. In this process, steam is introduced into a distillation chamber that contains the plant material. The steam breaks down the plant tissue, causing it to release its essential oil in a vaporized form. The vaporized essences, along with the steam and other substances, pass into a pipe through cooling tanks. The vapors return to liquid form and are separated from the water and captured as pure essential plant oil.
Lavender essential oil can range in color from pale yellow to yellow-green to colorless. The chief botanical constituents of the oil are the fragrance ester, linalyl acetate (up to 40%) and linalol, a terpene alcohol that is non-toxic to humans, yet naturally germicidal (30%). The combination of the sweet scent and the antimicrobial properties are key to lavender's effectiveness in cosmetic and aromatherapy preparations.
A label with the word "lavender" doesn't necessarily mean a product is a high quality true lavender essential oil, or that it will offer the aromatherapy benefits of true lavender. Over the past several years, demand for lavender oil has skyrocketed, creating a supply shortage that has led to adulterated and mislabeled lavender products making their way into the marketplace.
Some other common adulteration practices include spiking lavender and leavening oils with synthetic fragrances such as synthetic linalool and linalyl acetate to make it smell more like lavender, or stretching true lavender oil with solvents such as dipropylene glycol.
High quality true lavender oil has a sweet, floral, herbaceous and slightly woody aroma. There is almost no hint of camphor in true lavender since it contains a maximum of 1.5% camphor. Lavandin, the hybrid of true lavender and spike lavender, may contain 3% or higher levels of camphor, and its scent will be lavender-like, but with a stronger camphor note. Spike lavender can contain 8% or higher levels of camphor, offering a pungent, strong, camphor-like aroma.
Unfortunately, aroma can't always be relied on as a indicator of quality. Although an educated nose can tell when lavandin has been substituted for true lavender, identifying some adulterations, such as the use of odorless solvents to stretch true lavender oil, can often only be verified with lab analysis.