THE SCIENCE
High Altitude Lavender: The Production of Organic Compounds
By Rosalea Collinge
The hillsides of lavender at Running Springs Ranch are rich in fragrance and pollinators. The plants grow happily in northern California, which mirrors their native Mediterranean climate. At this farm in the mountains of Mendocino County’s North Coast Range, it’s not just the dry summers and cool winters that characterize the landscape, but also the altitude. At 2,300’ above sea level, these lavender plants are exposed to the rigors of the elements every day.
Secondary metabolites.
Environmental conditions affect plants in many ways, and one way plants respond is by altering the levels of organic compounds they produce 1. The group of compounds called primary metabolites contributes to processes like plant development and growth, photosynthesis, and respiration 2. The other group, called secondary metabolites, helps plants protect themselves from stresses like UV light, pests and diseases, and competition from other plants, as well as attracting pollinators and beneficial insects, and aiding in communication with other organisms 2.
While the secondary metabolites may be the least well documented of the two groups, these complex compounds have been important in human cultures throughout history, forming the basis of many medicines from ancient healing traditions to modern pharmaceuticals 3. They also have many other uses such as dyes, nutrients, fibres, flavourings, waxes, and oils, and it is likely there are many more applications waiting to be discovered 2. For example, scientific research is beginning to reveal their enormous potential as sources of natural insecticides, antibiotics, and new medicines 4.
One of the highest value aromatic plants in the world today, lavender has been important to many human cultures throughout history, including the ancient Romans and Greeks 5. The secondary metabolites in lavender essential oils have many useful properties, including strong antibiotic, antiviral, and antifungal action, and a potent scent and flavor, making them ideal ingredients in perfumes, soaps, soothing skincare products, and food and drink 6,7. They are also well known for their stress-reducing, sedative properties and are popular in alternative medicine and aromatherapy 8.
High altitude production
Plants cultivated for those useful properties that are conferred by secondary metabolites will contain varying levels of these important compounds depending on how and where they are grown, as well as the genetics of the plant itself. For example, plants often react to stress by producing higher concentrations of secondary metabolites, however they may also respond by reducing production, so this is a multifaceted subject 1. Each plant and the organic compounds it produces must be considered individually if a cultivator wants to maximize its secondary metabolite concentrations, and therefore its culturally and commercially important properties.
Altitude has been found to influence secondary metabolite composition and yield of essential oils in many aromatic and medicinal plants 9. For example in lavender, increases in altitude lead to increases in the production and accumulation of the secondary metabolite group known as terpenes, including the compounds linalool, linalyl acetate, terpinen-4-ol, (E)-caryophyllene, (E)-b-ocimene, and (Z)-b-ocimene 10.
Due to their biological properties, the significant components of lavender essential oil are considered to include linalool, linalyl acetate, camphor, borneol, 1,8-cineole, and terpinen-4-ol 11. Linalool is of particular interest due to its calming, anti-anxiety properties, as well as its anti-viral and antimicrobial action that is effective when this compound is present alongside linalyl acetate at high concentrations of a nearly equal ratio 12. Lavandulol is also considered important as it is one of the compounds that lends the flowers their distinctive floral scent and is therefore valuable for perfumiers 13.
Comparisons
Thanks to the development of sophisticated lab equipment and protocols, it is possible to measure the concentrations of organic compounds in plants. These tests are useful in many ways, including enabling cultivators to compare the quality of their produce with those grown in other locations or under different conditions.
In 2017, just one year after initial planting and despite the supplier’s advice that it would likely take three years, the lavender at Running Springs Ranch was ready to harvest. In 2018, the essential oil components of their Lavandula angustifolia ‘Royal Velvet’ and Lavandula x intermedia ‘Grosso’ flowers were lab tested by Eden Botanicals. The following graphs show results from these tests compared with those from plants cultivated in France and Spain, also using results from Eden Botanicals. All tests were performed using essential oils obtained from flowers through steam distillation.
Figure 1. Percentage of essential components in samples of Lavandula angustifolia cultivated organically in France, L. angustifolia cultivated at high elevation in France, and the cultivar L. angustifolia ‘Royal Velvet’ grown at Running Springs Ranch, Mendocino County, California, under organic conditions at high elevation.
As fig. 1 shows, linalool and linalyl acetate were the two most abundant components of all L. angustifolia plants tested. The L. angustifolia ‘Royal Velvet’ from Running Springs Ranch had higher concentrations of linalool than those grown in France, while levels of linalyl acetate were higher in plants grown in France. The plants cultivated at high elevation in France produced more linalool and linalyl acetate than those grown organically in France.
Figure 2. Percentage of essential components in samples from Lavandula x intermedia ‘Grosso’ cultivated in Spain and L. x intermedia ‘Grosso’ grown at Running Springs Ranch, Mendocino County, California, cultivated under organic conditions at high elevation.
The L. x intermedia ‘Grosso’ comparison (fig. 2) also shows linalool and linalyl acetate to be the two most abundant compounds in all plants tested, with Running Springs Ranch having higher levels of both than the plants grown in Spain.
As fig. 1 and fig. 2 show, the percentage of important compounds in L. angustifolia ‘Royal Velvet’ and L. x intermedia ‘Grosso’ cultivated at Running Springs Ranch is similar to, and in some cases exceeds, the tested plants from France and Spain. This reaffirms the fact that while lavender is not native to California, the climate is ideal for its cultivation. Fig. 1 also echoes scientific studies suggesting that high elevations do increase levels of linalool and linalyl acetate in lavender.
Harvest time
A 2014 study demonstrated that essential oil quality in flowering L. angustifolia ‘Etherio’ plants was influenced by environmental and developmental factors at the time of harvest 14. This study suggests that the best time to harvest lavender flowers for their essential oil content is when temperatures exceed 78.8 degrees Fahrenheit, when 60% of the flowers are in bloom, and only if no rainfall has taken place for ten days as this can temporarily decrease linalool production 14.
During the harvest period of May to July, the weather is dry and hot at Running Springs Ranch, and the lavender is grown on steep, south-facing slopes, an ideal position to make the most of the sun’s heat and light. The test results from Eden Botanicals show how well these plants compare to those grown in its native ranges, with high levels of culturally and economically important secondary metabolites.
Anecdotal evidence from many people who have used the oils produced at Running Springs Ranch attests to their pure, deep, unique fragrances. There are many known and unknown factors that influence a plants' secondary metabolites. It is likely that the high altitude at Running Springs Ranch contributes to the high quality of the essential oils produced here, along with the conditions at harvest, other environmental factors, cultivation practices, and the genetics of the plants themselves. There is without a doubt something in the air at Running Springs Ranch that makes their lavender special.
Rosalea Collinge grew up in Scotland and has a BSc in Horticulture (Plant Science) from Eden Project Learning and an MA in English and Philosophy from the University of St Andrews. She can be contacted at rmcollinge@gmail.com.
References:
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(10) Jan, S., Kamili, A. N., Parray, J. A., and Bedi, Y. S. (2015) ‘Differential response of terpenes and anthraquinones derivatives in Rumex dentatus and Lavandula officinalis to harsh winters across north-western Himalaya’ Natural Product Research, 30(5).
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(14) Hassiotis, C.N., Ntana, F., Lazari, D.M., Poulios, S., and Vlachonasios, K.E. (2014) ‘Environmental and developmental factors affect essential oil production and quality of Lavandula angustifolia during flowering period’ Industrial Crops and Products, 62, pp. 359-366.
