Essential Oil of Thyme: Cultivation and Production

Thyme is a perennial plant belonging to the Lamiaceae family (like Sage and Mint). It has the appearance of a small bush, no more than 30 cm tall, which in spring produces a large quantity of pink or white flowers. It is a plant with an unmistakable aroma that grows very easily in the Mediterranean area, even spontaneously, and has various uses, from culinary (seasoning, liqueurs) to health and cosmetic (mother tinctures, herbal teas, essential oil).

Thyme represents, therefore, an essential plant, destined not only for drying but also for the production of essential oil.

How could a medium-small agricultural company produce thyme essential oil?

The purpose of this article is to provide an overview in this direction, starting from a cultivation hypothesis and reaching the distillation process.

Cultivation of thyme:

As mentioned, it is a perennial species, but normally for economic and yield reasons, it is kept in cultivation for no more than 3-4 years, after which the plants tend to lignify. It could be extended to 4-6 years of planting, but it should be noted that old plants do not tolerate cuts to the base of the stem well, especially if not carried out annually.

Thyme multiplies by cuttings or by division of the clump, ensuring good crop uniformity. But it is also possible to propagate by seed, either directly in the field on a good seedbed with well-refined soil, or by transplanting seedlings previously obtained in a nursery.

Planting is done in spring or even in autumn in milder environments (where the seedlings are not damaged by winter frosts). In the second case, the harvest can be carried out earlier and with higher yields.

Generally, the planting density is around 4-5 plants/sqm, especially if destined for dried production. However, if the cultivation is intended for essential oil production, a denser planting density of about 6-8 plants/sqm is possible, with a spacing of 50-70 cm between rows and 30 cm between plants.

Yields in fresh product range from 4000-5000 kg/ha in the second year of production up to 8000-10000 kg/ha in the third-fourth year, then declining again in subsequent years.

Fresh thyme has an essential oil content that is approximately 0.5-0.8%. Considering the production of fresh plants per hectare and their average yield in essential oil, it is possible to obtain approximately 20 to 80 kg/ha of essential oil, depending on the year of harvest.

Thyme: Cultivation and production hypothesis:

Suppose you have a space of 800 square meters dedicated to thyme cultivation, and considering a planting density of 6-8 plants/sqm, you should have 4800-6400 plants to develop your field, from which it will be possible to obtain, in full production, about 640-800 kg of fresh product. Considering the lower yield in essential oil (0.5%), it is possible to obtain at least 3-4 kg of total thyme essential oil from fresh thyme.

With a distiller capacity of 125 liters, capable of processing approximately 25 kg of fresh plant material per distillation, it will be necessary to carry out 25 to 32 distillations at full load to process all the plant material and obtain the aforementioned quantity of essential oil.

Assuming 4 distillations per day, it will take 7-8 days of work.

To halve the working days, a 250 liter distiller, capable of processing about 50 kg of fresh material per single distillation, could be used.

Thyme Distillation:

Proceeding in order, let’s see all the phases, step by step, of how thyme essential oil is produced using a 125 liter capacity distiller.

Required equipment:

• Distiller with a capacity of 125 liters
• Flowering thyme sprigs, about 22-25 kg
• Running water
• Gas stove

Phase 1 – Harvesting of Plant Material:

The first thing to do is to cut the plants in full bloom, making a low cut a few centimeters from the ground (3-5 cm), but not too much, in order not to damage the basal shoots, and guarantee the future regrowth of the plants. On fertile and well-irrigated soil, it is possible to carry out two harvests a year.

It is important to remember that thyme essential oil is contained in the glandular hairs on the surface of the leaves, so it is not necessary to shred the plant material for distillation. It is also useful to keep the sprigs intact and not to use only the leaves; to ensure better and more homogeneous passage of the steam, and to avoid the harmful “cork effect” due to packing of the leaves during distillation.

Phase 2 – Loading the Distiller:

Once the plant material has been harvested, it is important to proceed with distillation as quickly as possible to avoid leaving the plant material piled up for too long, triggering harmful fermentation phenomena.

After assembling the distiller and connecting all the connecting tubes for loading and unloading the cooling water, it is possible to introduce water into the bottom of the boiler, up to the overflow of the bottom grid, and then load the plant material.

The plant material should be introduced into the boiler by distributing the sprigs evenly, creating almost layers. It is very important to press the material well, even pressing it with your feet, without fear of crushing it too much; insisting especially near the walls of the distiller to avoid the formation of empty spaces through which the steam can flow without coming into contact with all the leaves.

Once loading is complete, proceed to place the upper grid over the sprigs to keep them all inside the boiler. Then close the distiller with the appropriate hinge.

At this point, the stove is turned on to heat the water.

When the internal temperature reaches 50-60 degrees Celsius, open the cooling water for the condensation circuit.

Phase 3 – Distillation:

Once the temperature exceeds 50°C, the temperature of the distiller rises quite rapidly, and already around 85°-90°C, the first droplets of distillate will be seen coming out.

At this point, all that remains is to monitor the temperature of the cooling water in the condenser, which must remain warm.

Allow distillation to continue until the level of essential oil stops increasing inside the graduated collection burette.

Phase 4 – Packaging of the Essential Oil:

Once distillation is complete, all that remains is to separate the essential oil from the aromatic water, easily distinguishable inside the glass burette.

To facilitate the procedure, it is possible to pour the contents of the burette into a separating funnel, let it rest for the right time, and gradually open the tap of the funnel, allowing the hydrosol to drip first and then the thyme essential oil into a suitable amber bottle.

Explore further with a video dedicated to domestic thyme distillation.

Phase 5 – Maturation and Storage:

As with any freshly distilled essential oil, a maturation period is necessary before fully enjoying its fragrance.

Regarding storage: essential oil is a very delicate substance that can easily oxidize and deteriorate, losing its natural scent and developing substances that can also be harmful. Therefore, it is important to always store it in dark glass bottles, away from direct light and heat sources.

As we well know, essential oils are used drop by drop; their use must be limited to small quantities, as these substances are highly concentrated and rich in active molecules, many of which can also have toxic effects. Therefore, it is always necessary to proceed with caution when using them, also seeking advice from experts.

And now all that remains is to label all the bottles of thyme essential oil properly!

LAURA EDERLE in collaboration

with CELESTE MELCHIORI