Origanum spp. A member of the Lamiaceae (mint) family. [For Origanum majorana, see Marjoram.]

Botany: Oreganos are aromatic, herbaceous perennials with erect, hairy, square stems growing one to three feet in height. Leaves are opposite, toothed or toothless, oval, pointed, dull gray green, and up to two inches long. Flowers appear from July through September. They are quarter of an inch long, tubular, two-lipped, rose-purple to white, with four protruding stamens, and arranged in terminal spikelets about one inch long. Fruit contain four seedlike nutlets.

Use. Native from the Mediterranean region to central Asia. Origanum vulgare has naturalized in the eastern United States. Oregano, "joy of the mountain" in Greek, has medicinal, culinary, cosmetic, craft, and companion planting uses. Oregano can be used fresh or dried as a culinary herb. Its strong, biting aroma and sharp, piquant, somewhat peppery flavor is stronger-tasting than its relative marjoram. It is used in the cuisines of Italy, Greece, Brazil, Mexico, Spain, Cuba, and Colombia. Its flavor combines well with garlic, thyme, parsley, and olive oil. European colonists brought oregano to North America, where it spread to grow wild and is now routinely listed in wildflower guides. Fresh leaf sprigs or dried flowers can be used in arrangements and wreaths. Oregano or its oil is used in baths. The balsamlike odor of the whole plant makes it a good addition to potpourris, sachets, and aromatic waters.

Climatic Requirements Oregano is hardy in zones 4 to 10. According to Simon, Chadwick and Craker oregano has a reported life zone of 41 to 82 F.

Propagation and Care Oregano thrives in full sun in well-drained, average soil with a pH of 4.5 to 8.7 (Simon, Chadwick and Craker).

The flavor of oregano varies greatly when grown from seed. If this is a concern, and you must use seed, plant a lot so you can select plants with desired flavor. Seeds are tiny--130,000 to the ounce. At optimum germinating temperature of 70°F in the light, they should germinate in about 4 days; at less optimum temperatures, germination will take up to 14 days. If seeded outdoors in soil above 45°F, cover seeds with cheesecloth until the seedlings start to poke through, to keep them from being washed away in rain or irrigation.

For culinary use, propagating by cuttings or root divisions of plants with especially flavorful foliage is preferred. O. heracleoticum is more flavorful than O. vulgare. Take root divisions or cuttings in the spring.

Space plants 12 to 15 inches apart in rows 18 inches wide after danger of frost has passed. Oregano is a vigorous grower needing little attention. Plants mature in 45 days. Fertilize yearly with a balanced plant food; little water is needed after plants are established. Mulch plants to keep foliage clean.

Oregano is susceptible to root rot and fungal disease, and it can become infested with spider mites, aphids, or leaf miners.

A few sprigs of leaves can be cut when the plant is only six inches high; this makes the plant bushier. Essential oils are the greatest just before the plant blooms; foliage tastes sweeter if clipped before flowers begin to develop. Trim all branches, leaving only the lowest set of leaves; the plant will leaf out again within two weeks. This will provide another overall harvest in August; foliage developing after that should be left to support the plant through the winter.

Divide plants every couple of years, or they get woody and unproductive.

To dry hang oregano upside down in a dark, dry place. It dries very fast and retains most of its aroma and flavor. Discard stems, and store crisp leaves in airtight, light-tight containers.

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. See Figure 1. 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 Origanum vulgare is a fast spreader with little culinary use--its flavor is of lawn grass. It is grown for medicinal use or its pink flowers which dry well and are used for floral arrangements.

For best culinary flavor, grow "Greek" oregano--O. vulgare subsp. hirtum (also known as O. hirtum, O. heracleoticum, or O. vulgare prismaticum) or O. vulgare 'Viride.' These have more oil glands in the leaves, so they have a stronger flavor.

Also useful in the kitchen are "oreganos" that aren't true oreganos at all but are more heat-tolerant in the garden. Lippia graveolens--"Mexican" or "Puerto Rican" oregano--is a tender perennial member of the verbena family with cream-colored flowers and ovate leaves; it can be grown outdoors in the south and Southwest or indoors in containers in a sunny, south-facing window. Poliomintha longiflora, a native of Monterrey, Mexico, takes full sun or partial shade, tolerates freezing, and produces bright pink tubular flowers during the summer; its taste and woody nature are similar to winter savory.

O. vulgare var. aureum--Creeping Golden Marjoram--is fast-spreading, good in pathways and rock gardens. Cretan Oregano or Pot Marjoram is strong-flavored. Cuban Oregano has almost-round leaves with small, shallow, rounded teeth on the edges. Syrian Oregano has a strong spicy flavor. Trailing Oregano is good in hanging baskets or on rock walls.

Seed/Plant 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.

Henry Field's Seed & Nursery Co., Shenandoah, IA 51602.

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

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

Johnny's Selected Seeds, 299 Foss Hill Rd., Albion, ME 04910.

Le Jardin du Gourmet, PO Box 75, St. Johnsbury Center, VT 05863.

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

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

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

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.

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

The authors are:Yvonne Savio, Vegetable Crops Extension, UCD and

Curt Robinson, University Extension, UCD

Reviewed by Jeanine Davis, 12/4/91

Reviewed by Tim Hartz, 1/7/92

1/10/92