Herb Garden Plants: Oregano

Botanical Name: Origanum vulgare (oh-rih-GAY-num vul-GAR-ay)

Family: Lamiaceae (lay-mee-AY-see-ee); mint

History and Etymology:  The name oregano is derived from the Greek oros, meaning 'mountain,' and ganos, meaning 'joy.' The plant, Origanum vulgare, grows wild in the mountains of Greece and is commonly called wild marjoram. The Greeks used it as a poultice for wounds. Pliny, the ancient Roman writer, recommended it for scorpion and spider bites. Centuries later, colonists brought it to North America, where it escaped gardens and eventually naturalized along roadsides and in fields. 

Description:  Oregano's creeping rootstock produces square, hairy, erect, purplish stems. The small flower, which blooms in colors from white to purple, is ¼ inch long, two-lipped and tubular, and grows in terminal spike-like clusters. The leaves are opposite, ovate, and up to 2 inches long. Dried leaves are a popular herb used in many culinary products. The fruit is comprised of four seedlike nutlets. 

Plant Type and Hardiness: Oregano is a perennial that thrives in USDA Plant Hardiness Zones 5–8.

Height and Width:  Height 12 to 24 inches; width 10 to 20 inches. 

Light and Soil:  It grows best in full sun with well-drained, average soil with a pH of 6.8. 

Bloom Color and Time: Oregano blooms from July to September, with flower colors ranging from white to purple. 

Cultivation: A vigorous plant, oregano is low-maintenance. After about 6 inches of growth, pinch back tips to encourage more shoots. Once established, oregano requires little water. As it is drought-tolerant, wait until the soil dries out between waterings. Plants in pots require some supplemental irrigation. A balanced fertilizer can be applied annually. Cut out old wood that becomes leggy at the end of winter and replace plants every four years.

Propagation: Use seeds, cuttings, and root division, all in spring. Seed sowing can be accomplished either directly outside in rows 19–24 inches apart, then thinned to about 8–12 inches between plants, or under lights to produce transplants. Germination occurs in approximately 4 days in warm soil. Transplant when seedlings reach about 3 inches in height. When propagating through cuttings, wait for late spring, once the leaves are firm enough to prevent wilting. First, be sure to taste them for good flavor. Take softwood cuttings from a few new shoots about 3–5 inches long, cut at a 45-degree angle with a sharp knife, removing the bottom leaves, then plant in a sandy medium. Once they are well-rooted, re-pot them.

Pests and Diseases: Oregano can be susceptible to fungal diseases such as mint rust and root rot. Some potential insect pests include leaf miners, thrips, and cutworms. Aphids, spider mites, and white flies, which are often repelled by the aroma of oregano emitted by mature plants, can be a problem for young seedlings.

Companion Planting: The aroma of mature oregano can make it an excellent companion plant for tomatoes. Aphids, whiteflies, and spider mites are confused and repelled by the strong scent. In addition, flowers attract pollinators like honeybees, as well as ladybugs and hoverflies, which are natural predators of some tomato pests. Because tomatoes require different moisture conditions, one method is to plant oregano in pots around the tomato plants. An interesting study on oregano as a biofumigant found that, as an amendment, incorporating oregano directly into the soil can increase tomato yields by 77%–95%.

Harvesting:  Harvest in summer or early autumn, before the plants are in full flower. Up to ¾ of the current season's growth can be gleaned at one time. Cut the stems, with flower heads attached. Tie small bundles, place them in a ventilated paper bag, and hang them indoors. Once dry, store leaves in an airtight container for up to 6 months for a pungent and flavorful herb. Oregano can also be dehydrated in a dehydrator, microwaved, baked in a low-temperature oven, or even frozen for shorter periods.

Herbal Uses:  Oregano is used in a wide variety of culinary, decorative, medicinal, and cosmetic products. Fresh or dried leaves flavor tomato sauce, vinegar, butter, omelets, quiche, bread, marinated vegetables, beef, poultry, game, onions, black beans, and zucchini. Dried flowers are found in decorative arrangements and add a pleasant fragrance to potpourris. Fresh sprigs are woven into wreaths. Oregano is also used to make red dye. It has attractive flowers and can be grown in containers. Oregano essential oils, with high concentrations of carvacrol and thymol, possess antimicrobial and anti-inflammatory properties. Oregano was used traditionally for digestive and respiratory problems.

Garden Notes:  With its low, compact growth, oregano makes a good border plant. Once in bloom, plants produce flowers throughout the growing season. Pinch back to encourage bushier growth. Oregano is closely related to marjoram, but it has a coarser texture and a stronger flavor.