Thymus vulgaris. A member of the lamiaceae (mint) family.

Thyme is a small, sub-erect, many-branched, aromatic perennial shrub that grows up to a foot high and two feet wide. Leaves are arranged oppositely in pairs, are oblong-lanceolate, stalkless or nearly stalkless, a quarter to half an inch long, with edges rolled under and pale, hairy undersides. Numerous flowers appear from spring through fall but mostly in June and July. They are tubular, lilac to pink, under quarter inch long, and arranged in small terminal clusters. Fruit contain four tiny seedlike nutlets. Native to the western Mediterranean region.

Use: Thymol, the essential oil of thyme, has a long list of historical medicinal uses. Thyme has a strong, herbal and pungent taste. Its flavor is sometimes confused with marjoram, but thyme is stronger, and is at its best when used in long, slowly cooked dishes, or as a marinade.

Leaves and sprigs are used as seasoning in clam chowder, stuffing, with meats, flavored vinegars, pickles, and mustard. Thyme is used to flavor liqueurs and is one of the flavorings in Benedictine liqueur. The flowers are edible. The oil is used in flavoring toothpastes, mouth washes, and cough medicines.

Thymol's antiseptic and stimulating properties are useful in colognes, after-shave lotions, soaps, and detergents.

Thyme flowers comes in pink, lavender, crimson, or white, and the plant makes both a windowsill herb and an outdoor edging plant. Thyme works well as a groudcover and tolerates light traffic. Bees like the tiny blossoms. The dried flowers have been used to preserve linen from insects. Leaves and flowers are ingredients in sachets.

Yield. Yields may be up to 1,500 pounds of the dry herb per acre, or some 20 pounds of the essential oil per acre.

Climatic Requirements: Thyme has adapted to conditions that range from tropical Mediterranean areas to Scandinavian and Siberian cold, from sea level to 4000 meters, with rainfall of 0.5 to over 100 inches per year, and in soil pH of just over 4 to almost 8. Successful growing of most thymes is therefore possible in any climate having a mean annual temperature anywhere from 45 to 70°F.

Propagation and Care: Thyme may be grown from seed or propagated by division. Sow seeds 1/4 inch deep and 2 feet apart. Set roots 1.5 feet apart in rows 2 feet apart . Growth during early stages is slow. Side-dress with well-rotted compost each spring.

Thyme requires relatively little care, doing best in direct sun with little water. Since leaves are the desired product, soils rich in nitrogen are most desirable. Well-drained soil is mandatory as the plant is susceptible to fungal diseases. Protect plants from deep frost with a mulch. Low, creeping thyme ground covers withstand winters better than bushy varieties, but they are vulnerable to poor soil drainage.

Divide, take cuttings of new green growth, or layer green or woody branches of established plants from midspring through early summer. Replace or propagate culinary varieties every two or three years as they become woody, straggly, and produce few tender leaves.

Harvest leaves of established plants as needed; they are most fragrant on a dry day before noon just before plants bloom. Entire plants can be cut back about two inches from the ground; new foliage will fill in again before cold weather, but harvesting this second crop will make it less winter hardy. Tie harvested stems in bunches and hang to dry in a warm, airy place; or place stripped leaves on a thin screen to dry, out of direct light--forced air dehydrators at temperatures of 115 to 125°F can be used. Store in an airtight and light-tight container. Leaves can also be frozen.

Postharvest Handling (section by Marita Cantwell). Increased use of fresh herbs for culinary and other purposes has also increased the demand for high quality. The successful marketing of high quality fresh culinary herbs requires extreme care and attention to postharvest handling conditions.

All the postharvest principles that apply to leafy green tissues apply to the handling of fresh herbs. Temperature is the single most important factor in maintaining quality after harvest. Despite the diverse botanical origin of the fresh herbs, the optimum postharvest temperature for fresh thyme, oregano, rosemary, mints, sage, parsley, cilantro, savory, marjoram, dill, and tarragon is 32 F (0 C). Under controlled conditions, a shelf life of 3 to 4 weeks can be achieved at this temperature. With a temperature of 41 F (5 C), a minimum shelf life of 2 to 3 weeks can be expected. If herbs are harvested early in the morning, the need for cooling is minimized. If harvested later, the appropriate cooling method depends on the type of herb. Most respond favorable to room and forced air cooling. Herbs have also been successfully vacuum-cooled. A simple forced air pre-cooler can be constructed for small operations that requires only an adequate coolroom, a fan, and some simple carpentry.

After temperature, prevention of excess moisture loss is the second most important postharvest factor affecting the quality and shelf life of herbs. Most herbs respond favorable with very high humidity (>95%). Some herbs can be held successfully in water (basil, mints, tarragon), whereas water loss in most can best be controlled by packaging and maintaining high humidity in the environment. Lowering the holding temperature to the recommended levels also greatly reduces water loss.

Herbs can be packaged in bags designed to minimize water loss. When herbs are packaged this way, it is particularly important to maintain constant temperatures, to reduce condensation inside the bag and the consequent risk of fungal or bacterial growth. The bags may be partially ventilated with perforations, or may be constructed of a polymer that is partially permeable to water vapor.

The relative humidly in the packing area, cold rooms, and transport vehicles should be maintained at a high level (>95%) where practical.

Ethylene gas is another factor which limits the shelf life of leafy tissues. Ethylene causes yellowing of leaves, and an increased rate of deterioration. It is possible to routinely find one to three ppm ethylene in the environment surrounding fruits and vegetables during commercial handling. Young growing herb tissue responds to ethylene (5 ppm), whereas little effect was observed in mature herb cuttings. In addition, holding the herbs at the recommended temperatures also greatly reduces their ability to respond to ethylene in the environment.

Careful handling to avoid physical injury to the leafy tissue of the fresh herbs is also important. Rigid clear plastic containers such as those sometimes used for sprouts may be used for soft herbs. "Pillow packs" (plastic bags which are partially inflated when sealed) may be an alternative packaging technique. Careless handling results in tissue discoloration, as well as increasing sites for pathogen attack. Growth of microorganisms can also be reduced by proper temperature management and good hygienic practices in the field and packing station. Chlorinated water can reduce microbial load if water is used during handling.

Varieties: Of the 150 to 400 species of thyme, that exist, these are some of the most common.

Others: Coconut, Doone Valley Lemon, Dwarf, German Winter, Golden Lemon, Golden Creeping, and Oregano.

Seed Sources:

W. Atlee Burpee & Co., 300 Park Avenue, Warminster, PA 18974.

De Giorgi Co., Inc., PO Box 413, Council Bluffs, IA 51502.

Gurney's Seed & Nursery Co., Yankton, SD 57079.

Harris Seeds, 961 Lyell Avenue, Rochester, NY 14606.

Indiana Botanic Gardens, PO Box 5, Hammond, IN 46325.

J.L. Hudson, Seedsman, PO Box 1058, Redwood City, CA 94064.

Nichols Garden Nursery, 1190 North Pacific Hwy., Albany, OR 97321.

Park Seed Co., Cokesbury Road, Greenwood, SC 29647-0001.

Peace Seeds, 2385 SE Thompson Street, Corvallis, OR 97333.

Pinetree Garden Seeds, Route 100, New Gloucester, ME 04260.

Redwood City Seed Co., PO Box 361, Redwood City, CA 94064.

Otto Richter & Sons Ltd., Box 26, Goodwood, Ontario, Canada L0C 1A0.

Seeds Blum, Idaho City Stage, Boise, ID 83706.

Shepherd's Garden Seeds, 30 Irene Street, Torrington, CT 06790.

Stillridge Herb Farm, 10370 Route 99, Woodstock, MD 21163.

Stokes Seeds Inc., Box 548, Buffalo, NY 14240.

Taylor's Herb Gardens, Inc., 1535 Lone Oak Road, Vista, CA 92084.

Territorial Seed Co., PO Box 27, Lorane, Or 97451.

Thompson & Morgan, PO Box 1308, Jackson, NJ 08527.

Otis Twilley Seed Co., PO Box 65, Trevose, PA 19047.

Vermont Bean Seed Co., Garden Lane, Fair Haven, VT 05743.

References:

Cantwell, M. and M. Reid. Postharvest handling of fresh culinary herbs. Perishables Handling No. 60: 2-4. Vegetable Crops Dept., UC Davis. 1986.

Joyce, Daryl, Michael Reid and Philip Katz. Postharvest handling of fresh culinary herbs. Perishables Handling No. 58:1-4. Vegetable Crops Dept., UC Davis. Feb. 1986

Figure 2. Thyme. Photo by Hunter Johnson.

Figure 3. Lemon thyme. Photo by Hunter Johnson.

By: Yvonne Savio, Vegetable Crops Extension, UCD and Curt Robinson, University Extension, UCD

Reviewed by Jeanine Davis, 12/04/91

Reviewed by Tim Hartz, 1/7/92

1/10/92