Harvesting as with any crop is very exciting with the soothing aroma beautiful purple fields. However, the window of time to harvest lavender at it’s peak of its quality is short, and this can mean very long hours. Harvesting and timely handling of the crop or the can mean the difference between success and failure.
Timing. Proper timing of the harvest depends upon the end product. Lavender grown for either fresh-market or dried bundles, should be harvested when the first one or two flowers have bloomed on the stem. If the flowers are in bloom at harvest, the bundles will drop most of the flowers and buds from the stems after drying. If the end product are buds, then lavender should be harvested when approximately one-quarter to one-half of the lavender flowers on the stem are in bloom. However if the end product is essential oil the optimum time to harvest is when approximately half of the flowers on the stem have withered. The oil accumulation is at its maximum, and quality is typically at its peak.
Harvesting for Oil Distillation. Lavender harvested for essential oil distillation should be harvested with enough stem attached to properly pack the still pot being used. Leaving a good stem length will prevent the flower heads from being packed too tight in the still pot, preventing the steam from freely flowing uniformly through the lavender, thus reducing oil yields. Additionally, the stems contain some oil.
Harvesting for Quality. Lavender must be dry when harvested. Harvesting when wet can cause discoloration, mold in bundled lavender, and can potentially result in chemical changes in the essential oil that can reduce quality. It is also ideal not to harvest when it is very hot, which may cause wilting and oil reduction. The best time for harvest is from mid-morning until early afternoon.
Yields: The harvest of dried lavender buds and bundles will vary depending on the variety, however on the average, mature plants should yield between 4 and 6 bundles per plant (bundles averaging about 150 stems per bundle).
Drying: Lavender should be dried as soon as possible after harvest, as this insures the highest quality and color. Lavender is typically dried in small bundles hung upside down in a dark, well-ventilated area. The lavender is gathered in small bundles held together with a rubber band. The rubber band keeps the bundle tight as it provides the elasticity needed as the bundles shrink during the drying process. The lavender bundles are usually hung using a paper clip with one end bent to hang with and the other end hooked through the rubber band of the bundle. The bundles are hung in a variety of methods, some are hung on wire or individual hooks. Whichever method of hanging is utilized for the lavender bundles, it is important to insure enough space is provided between bundles to allow good air flow. Low humidity is also important in the drying process as high humidity can cause lavender to mold. If the dried lavender is intended to be used for loose lavender buds, then the lavender buds should be stripped as soon as possible after it is dry, and the buds placed in sealed containers.
Oil Extraction: Most of the lavender grown around the world is grown for its essential oil. However, most US lavender producers are small farms that produce high-value products and aesthetically pleasing experiences for customers and tourists. Lavender essential oils are primarily used in cosmetics, perfumes, soaps, detergents, air freshener, cleaners, and, increasingly, for aromatherapy and homeopathic medicine.
Essential oils are volatile oils that can be extracted from plants using a simple steam because they are in any way essential or necessary for any given purpose, but because they are considered the “essence” of the plant. Essential oils have been used for many centuries for a wide variety of purposes.
Capital investment, transportation, and labor (cost and availability) dictate that most essential oils production is produced outside the US However, most of the essential oil produced in the US is orange oil, which can be cheaply produced as a byproduct of the citrus juice industry. The next largest volume is cedar oil, a byproduct of the forestry industry. Statistics on lavender oil production around the world are difficult to obtain. By far, the largest and best-known lavender production is southern France. England historically has been a significant producer of lavender oil, but in recent years, has declined considerably. And as previously indicated, US lavender farms, are more dependent on tourism and product development than on producing bulk lavender oil. Other countries are rapidly expanding lavender production such as China, Australia, Russia, Bulgaria, Yugoslavia, Hungary, Argentina, and New Zealand.
There are several methods to derive essential oils from plants. Hydro distillation (also known as water distillation) is a process in which water and plant material are boiled together in a vat. The result is a “hydrosol” rather than a pure essential oil. Hydrosols are the basis for a variety of retail products. Steam distillation uses dry steam to vaporize and extract the oil. Steam distillation is used in large scale production of essential oils for commercial purposes. It is the preferred method for lavender. Steam distillation can be accomplished with a pressure cooker on top of a kitchen stove, but only a few drops of oil are produced per batch. Supercritical extraction uses carbon dioxide under extremely high pressure to extract both essential oils and oleoresins. Essential oil produced as a byproduct of the citrus industry requires a four story fractionating tower.
As indicated previously lavender oil primarily extracted using steam distillation. Lavender essential oil is extracted from the fresh flower heads and stems. A steam distillation unit has four basic components: steam generation, a still pot, a condenser, and a separator. The steam rises up through the lavender, which is suspended above the water in a basket contained within the still pot. Still pots are the container that holds the lavender. The steam escapes along with the lavender oil. As the steam moves through the lavender, the oil glands on the lavender flowers are ruptured, and the oil is quickly vaporized and moves with the steam. As the steam reaches the top of the still pot, it is piped to a condenser.
The condenser removes enough heat to allow the water vapor to condense and re-liquefy. The condenser is typically a long coiled tube that is bathed in cool water, which removes heat. Since lavender oil is lighter than water, it floats to the top of the water in the separator. The oil layer on the surface of the water is then skimmed off, while the water is removed from a lower outlet and saved some of this water as “hydrosol” and used to make various products. Oil should be stored in a cool, dark place in containers that are filled to capacity, and that have air sealed caps that will keep the oil from oxidation. Some aging of the oil in storage may be beneficial for a few months, however, essential oils stored for long periods of time will eventually deteriorate in quality.