Background

Thyme (Thymus vulgaris L.) is a perennial member of the mint family. Thyme has culinary and medicinal uses, and is used as a whole herb or distilled to produce an essential oil. Thyme herb and oil may be used for flavoring foods and in medicinal products and cosmetics.

Thyme has very small seeds and is generally started from transplants grown in the greenhouse. Mature plants should be harvested twice a season to prevent the accumulation of unproductive woody tissues. Harvest is normally at bloom. The foliage is dried and screened to produce various grades of herb.

Thyme oil is produced by steam distillation of the plant top. Plant material is dried before distillation (1). The essential oil contains thymol, carvacrol, borneol, p-cymene, linalool, and cineole (3). Both high and low thymol species are available. A longer distillation (8 hours) results in higher thymol content. Oil yield in Morocco from leaves and flowering tops only was 0.5 - 1.2%; oil yield for the entire top was 0.4 - 0.7% (3).

Research Summary

Thyme ‘German Winter’ (Johnny's Selected Seeds) was sown in the greenhouse on March 20, 1998, and transplanted to the field at the Western Agricultural Research Center on May 13. Six-row plots were 8 ft long with rows 18" apart and 10" between plants, with four replications. In 1998, the top 2/3 of the plants were harvested on July 29 when 50% of the plants were in bloom. Plants were harvested twice in 1999, on June 22 and August 20, again removing 2/3 of the foliage. Border rows were not included. Plant material was air-dried before distillation. In 1999, culinary-grade leaf was calculated.

Table 1. Yield of thyme at the Western Agricultural Research Center, Corvallis, MT
Date
Dry weight (lb/a)
Leaf (lb/a)
Oil (lb/a)
1998
 
 
 
Jul. 29
1,184
 
9.5
1999
 
 
 
Jun. 22
2,208
1,262
18.0
Aug. 20
2,178
1,245
20.4
Total 1999
4,386
2,507
38.4

Acknowledgements

Seed was donated by Johnny's Selected Seeds, Albion, ME.

References

  1. Jackson, S. and R. Hay. 1994. Characteristics of varieties of thyme (Thymus vulgaris L.) for use in the UK: Oil content, composition and related characters. J. Hort. Science 69:275-281.
  2. Hornok, L. 1992. Cultivation and Processing of Medicinal Plants. John Wiley and Sons, Chichester, UK.
  3. Guenther, E. 1948. The Essential Oils. Robert E. Krieger Pub. Co., Inc.
  4. Venskutonis, P. 1997. Effect of drying on the volatile constituents of thyme (Thymus vulgaris L.) and sage (Salvia officinalis L.). Food Chemistry 59:219-227.