How to Grow Thyme

Start with plants, divisions or cuttings

Thyme seed is tiny and germinates unevenly, and NC State calls common thyme difficult to propagate from seed. Penn State adds that seed-grown plants may take several years to grow large enough for a real harvest. Most gardeners buy a starter plant or take a piece of an established one.

Division is easiest in early spring: dig the whole root ball of a well-established plant and pull it into smaller pieces, each with roots attached. For cuttings, Penn State recommends 4-inch tips of new growth taken in late spring, stuck in pots of sand and kept well watered. Layering a low stem into the soil also works.

If you do try seed, Penn State says to sow in spring in a seed tray or scatter it on the ground, keep seedlings moist and thin to about 12 inches apart.

Choosing a thyme

Common or garden thyme (Thymus vulgaris) is the main cooking thyme. Penn State describes several cultivars: ‘Narrow Leaf French’, which chefs prefer for its lighter, sweeter taste; ‘Broadleaf English’, the most robust; and ‘German Winter’, very winter hardy with good flavor. University of Delaware Master Gardeners list English thyme at about 90 days, lemon thyme at 90 to 100 days and common thyme at about 180 days to harvest.

Lemon thyme (T. x citriodorus) has a light lemon taste and scent. Low species such as creeping thyme (T. praecox), only 2 to 3 inches tall, and woolly thyme suit rock gardens and the spaces between pavers. Colorado State notes creeping thyme can replace turf where foot traffic is light.

Hardiness varies by cultivar, so in cold regions look for a thyme sold specifically as winter hardy, as Oregon State advises.

Site and soil

Plant in full sun, at least 6 hours a day; Penn State and Colorado State say thyme tolerates partial shade. In the low desert, University of Arizona notes most herbs appreciate some afternoon shade during the hottest part of summer.

Drainage decides whether thyme lives through its first winter. NC State says it performs best in dry, sandy or rocky soil with a neutral to alkaline pH; Penn State gives a pH of about 6.3, so slightly acidic soil is fine too. In heavy clay, plant in a raised bed, a rock garden or a gravelly berm. Oregon State calls thyme well suited to a rock garden.

Space plants about 12 inches apart (Penn State and UC Master Gardeners of Orange County) or 10 to 12 inches (Texas A&M), in rows 12 to 18 inches apart. Common thyme forms a mound 6 to 12 inches high and up to about 16 inches wide.

Planting and care

Set plants out once the danger of frost has passed; the dates for your zone above show that window. Plant at the same depth as in the pot and water well.

Water: keep new plants moist while they establish, then water sparingly. Established thyme is drought tolerant, and wet soil does far more harm than dry. In the desert, University of Arizona recommends deep, infrequent watering of in-ground herbs and placing drip emitters carefully for creeping types such as thyme, which spread along the surface.

Fertilizer: none is needed once plants are established, according to Penn State.

Trimming: NC State recommends cutting back in early spring and again in summer to reduce woody growth, and trimming whenever plants get leggy. Even so, Penn State notes that plants eventually become overly woody and need to be replaced; division in spring renews them.

Winter: Colorado State suggests mulching thyme after the first of the year to prevent frost heaving and winter damage, and watering about once a month during dry winter periods.

Regional notes

• Cold north: choose a hardy cultivar such as ‘German Winter’, plant in spring in the best-drained spot you have, and mulch in midwinter. Where cooking thyme does not reliably survive, as Colorado State notes for Colorado, grow it as an annual or in a pot.
• Humid South and Gulf Coast: summer heat, humidity and wet soil are the threats. Plant in raised beds, give plants room for air flow and avoid wetting the foliage. In Florida, UF/IFAS treats thyme as a cool-season herb planted in late fall or early spring.
• Arid West and desert Southwest: thyme handles dry air well. University of Arizona lists October-November and February-April for planting in Tucson.
• Warm-winter zones 9-10: grow through the cool months and expect plants to struggle in a hot, rainy summer.

Harvesting and drying

Take only a few sprigs the first year so the plant can fill in. After that, the sources differ slightly on timing. Penn State and NC State harvest just before the plant flowers, when essential oil in the leaves peaks. UF/IFAS cuts the top third of the plant at full bloom. Either way, NC State advises cutting 5 to 6 inches of top growth and always leaving about 5 inches, including the woody base. Colorado State’s lighter approach is to cut 2 to 3 inches of stem tips as needed.

Pick on a dry morning, after dew dries and before midday. To dry, Penn State strips the bottom 2 inches of leaves, bundles the stems with a rubber band and hangs them upside down in a shady, dry, airy place. When the leaves are crisp, strip them off and store them in airtight containers.

Common problems

• Plants yellow, wilt and die, especially in winter: root rot, including Rhizoctonia, from wet, poorly drained soil. Move to a raised or gravelly bed.
• Gray mold or leaf spots: botrytis and Alternaria leaf spot, favored by humidity and crowding. Space plants and water the soil, not the leaves.
• Stippled leaves, fine webbing or clusters of small insects: spider mites or aphids. Rinse plants with water or use insecticidal soap.
• Sparse, woody plants: age. Trim yearly and divide or replace old plants.
• Plants pushed out of the ground in spring: frost heaving. Mulch after the ground freezes in midwinter.

Thyme is often grown beside rosemary, oregano, sage and lavender. That is a practical grouping because they share the same sun and dry-soil needs; Penn State says no companion-planting information is available for thyme.