How to Grow Oregano

Start with a plant you have tasted

Oregano grown from seed is unpredictable. University of Illinois Extension notes that seedlings may not be true to type and flavor varies, and NC State points out that some oreganos are ornamentals with little flavor at all. The surest route to good oregano is a cutting or division from a plant whose leaves you have tasted.

Penn State does all propagation in spring. For cuttings, wait until late spring when leaves are firm enough not to wilt, taste first, then take 3- to 5-inch softwood tips, cut at an angle, strip the lower leaves, and root them in a sandy mix before potting them up. Divisions are simpler: dig an established clump in spring and cut it into rooted pieces.

If you start from seed, sow indoors under lights. Penn State reports germination in about 4 days in warm soil; Illinois gives 10-14 days for herb seeds generally and says most herb seedlings are ready to plant out in about 10 weeks. Move seedlings outdoors once they are about 3 inches tall and frost danger has passed, after hardening them off over 5-7 days. Seed can also be sown directly outdoors in rows 19-24 inches apart and thinned to 8-12 inches between plants (Penn State).

Site, soil and spacing

Full sun and good drainage matter more than anything else. NC State notes that golden and variegated oreganos do better with some shade during the hottest part of the day, but green types want sun all day.

Sources differ on fertility. Texas A&M recommends rich soil, while Penn State calls for average soil with a pH around 6.8 and NC State for average soil including sandy loams. Iowa State explains the trade-off: herbs generally prefer low to moderate fertility, because very fertile soil produces plenty of foliage with reduced flavor. Unless your soil is very poor, skip the extra compost and fertilizer.

Spacing ranges from 8-10 inches (Texas A&M) and 9 inches in rows 18 inches apart (UC Master Gardeners, Orange County) to 8-12 inches in rows 19-24 inches apart (Penn State). Plants reach 1-2 feet tall and 10-20 inches wide (Penn State), and NC State notes oregano slowly spreads into a clump that can serve as a sunny ground cover.

Care through the season

Water new plants regularly until they root in. After that oregano is drought tolerant: Penn State waits until the soil dries out between waterings. Potted oregano needs extra irrigation, though it still likes the mix to dry slightly between waterings.

A light annual application of a balanced fertilizer is enough (Penn State).

Pinch the tips once stems reach about 6 inches to make the plant branch (Penn State), and shear it back regularly before flowering to keep new leaves coming (NC State). Iowa State notes that letting oregano flower can hurt the flavor of the leaves. At the end of winter, cut out old, woody, leggy stems. Penn State suggests replacing plants about every 4 years.

Harvesting and drying

Snip leaves as needed all season. For the best flavor, and for drying, harvest just as flower buds form, before they open (UF/IFAS, NC State). Iowa State recommends cutting in the morning after the dew has dried. Penn State allows up to three-quarters of the season’s growth to be cut at once in summer or early fall, and in Iowa a July harvest is often followed by a September one.

Tie small bundles, put them in a ventilated paper bag and hang them indoors to dry. Penn State stores dried leaves in an airtight container for up to about 6 months; oregano can also be frozen. In fall, Oregon State suggests cutting the long runners and keeping them in a glass jar in the refrigerator, where they stay fresh for several weeks.

Regional differences

Cold north. Oregano goes dormant in winter; Oregon State notes it is slightly less hardy than thyme and benefits from a warm spot such as a rock garden. Cut back long runners in fall. Penn State recommends mulching perennial herbs with about 4 inches of straw or evergreen boughs after the ground freezes to prevent heaving.

Humid South and Florida. Drainage is the main battle, because wet soil causes root rot. Plant in raised beds or pots and space plants for air flow. UF/IFAS’s North Florida calendar lists oregano in April and May and again in October, and its South Florida calendar suggests setting out small plants in July. Note that “Cuban oregano,” which also appears on Florida calendars, is a different plant.

Desert Southwest. University of Arizona Extension lists oregano for October-November and February-April planting in Tucson, with frost protection in winter. Herbs there generally benefit from afternoon shade in midsummer, and containers should be at least 14 inches across.

Problems

• Root rot. Caused by wet, poorly drained soil. Plant in well-drained beds or containers.
• Fungal diseases, including mint rust. Favored by humidity and wet leaves. Space plants and water at the soil.
• Aphids, spider mites and whiteflies. Mostly a problem on young seedlings; Penn State notes mature plants’ scent tends to repel them. Rinse plants or use insecticidal soap.
• Leaf miners, thrips and cutworms. Occasional pests (Penn State). Remove damaged leaves and protect new transplants.

Oregano near tomatoes

Penn State describes oregano as a good companion for tomatoes: its scent may confuse aphids, whiteflies and spider mites, and its flowers attract honeybees, lady beetles and hoverflies. Like most companion-planting advice this rests largely on tradition and observation; the one study Penn State cites found that oregano worked into the soil as a biofumigant raised tomato yields by 77-95%, which is a different practice from growing the two side by side. Because tomatoes need more water than oregano, Penn State suggests growing oregano in pots set around the tomatoes.