Thyme

Description

Thyme, Thymus vulgaris, is a small, perennial, evergreen shrub in the family Lamiaceae grown primarily for its leaves which are used as a herb. The thyme plant has an erect or ascending growth habit and possesses many woody, branching stems. The leaves of the thyme plant are linear or elliptical and are arranged alternately on the stems. The leaves are densely covered in minute hairs and have numerous red-brown oil glands on the surface which take the appearance of small dots. The leaves can be green or variegated. The plant produces whorls of tiny pink, lilac or pale purple flowers on a terminal spike and tiny brown fruits, each with one seed. Thyme can reach a height of up to 50 cm (20 in) and can be grown as an annual or a perennial. Thyme may also be referred to as common or garden thyme and originates from the Mediterranean.


Uses

Thyme leaves and flowers can be used fresh or dried as a herb in cooking. Bees which collect nectar from thyme flowers produce a high quality honey. Essential oil can be extracted from the leaves and is commonly used in the manufacture of perfume or as flavoring in toothpastes.


Propagation


Basic requirements
Thyme grows best in warm, sunny climates at temperatures between 4 and 28°C (39.2–82.4°F) but will grow best at 16°C (60.8°F). Established plants can survive temperatures down to -16°C (3.2°F). Thyme is tolerant of drought conditions but water-logged soil is detrimental to it’s survival and production. Thyme will grow best in well-draining, fertile sandy loam or sand. Thyme should be planted in alkaline soils and require full sunlight for optimum productivity.

Propagation
Thyme is propagated from seed and can be direct seeded or sown in a nursery to produce transplants. Thyme can also be propagates from cuttings, air layering or by division of the roots. When planting seeds, they should be covered should be covered with a thin layer of soil to prevent them from drying out while they germinate. Seedlings should be thinned to a final spacing of 10–15 cm (4–6 in) allowing 20–25 cm (8–10 in) between rows. Transplants can be planted in the field after hardening when they are 5–8 cm (2–3 in) tall. Cuttings should be taken from healthy, vigorous plants by taking a clipping about 7.6 cm (3 in) in length from the end of a branch. The leaves should be removed from the lower half of the cutting before planting in light textured potting media to root. The cutting should be watered regularly and kept moist, but not wet while they root. The new plants will be ready for transplanting after approximately 8 weeks. after hardening and are planted in the same way as seed-grown transplants.

General care and maintenance
It is common practice to mulch thyme plants with a layer of limestone gravel to suppress weeds, conserve soil moisture, improve drainage around the plant crown and reflect light back to the foliage. Once planted, thyme will grow adequately without fertilization, but will benefit from the occasional application of well aged manure or a balanced fertilizer. Similarly, thyme can withstand drought but will benefit from supplemental irrigation during dry periods. The soil should be allowed to dry out between waterings. Thyme plants should be pruned regularly by pinching off the tips of the shoots to promote branching.

Harvesting
Thyme is best harvested just prior to flowering when the essential oil content of the leaves is at its highest. Plants can also be harvested during flowering but the flowers are very attractive to bees and this may make harvesting more problematic at this time. Thyme is harvested by cutting the branches 8–10 cm (3–4 in) above the ground. Cutting can be done by hand or, in the case of commercial production, by machine.


References

CABI Crop Protection Compendium. (2008). Thymus vulgaris (thyme) datasheet. Available at: http://www.cabi.org/cpc/datasheet/53795. [Accessed 21 April 15]. Paid subscription required.

Copsey, K. & Lerner, B. R. (2002). Growing herbs. Purdue University Cooperative Extension Service. Available at: http://www.hort.purdue.edu/ext/HO-28.pdf. [Accessed 09 April 15]. Free to access.

Herb Society of America (2003). Thyme. An Herb Society of America Fact Sheet. Available at: http://www.herbsociety.org/factsheets.... [Accessed 21 April 15]. Free to access.


Common Pests and Diseases

Alternaria blight
Alternaria brassicicola

Symptoms
Small, round, yellow, brown or black spots with concentric rings which appear first on lower shaded leaves; holes in leaves caused by lesions drying and dropping out; leaves dropping; death of plant
Cause
Fungus
Comments
Spread by infected seed; use wide plant spacing to promote air circulation
Management
Remove and destroy infected leaves; use wide plant spacing to promote air circulation around foliage