Thyme (Thymus spp.) has been cultivated for many centuries. The genus Thymus contains more than 300 different species and is in the mint family (Lamiaceae). Thyme has been valued throughout history for its fragrance, flavor, and ornamental value.

Thyme is a semi-evergreen groundcover that rarely grows more than 15 inches tall. Thyme has both prostrate and upright habits. Its stems can become woody with age. Thyme leaves are small, usually 1/2 inch or less in diameter and oval to oblong in shape. It also is highly aromatic with each species having a slightly different scent.

The tubular-shaped flowers occur in dense, terminal clusters and blanket plants in summer. Flowers also sometimes form in the leaf axils of the plant. Flowers usually are lavender, red, or white depending on the cultivar. The flowers are very attractive to bees, and the honey made from thyme-fed bees is considered a culinary delicacy.

Culture

All species of thyme prefer full sun and a well-drained soil. In fact, most thyme species do best in coarse, gritty soils that would be unsuitable for many other plants. Thyme can develop root rot and is susceptible to fungal diseases if grown in wet soils. Thyme should not be fertilized heavily because over-fertilized plants will become tall, spindly, and weak. Plants used for culinary purposes should be replaced every few years to prevent the development of any undesirable, woody growth.

Thyme is hardy in USDA Hardiness Zones 5-9, but can "melt out," or decline, during hot, humid summers. Cutting plants back will help them recover. Generally, prostrate forms of thyme overwinter better in Iowa than upright types. Thyme is easy to propagate from seed, cuttings, and division.

Uses

Only a few thyme species are used as landscape ornamentals. Thyme is excellent for rock gardens. Sunny windowsills are also great locations for containerized thyme. Creeping thyme will tolerate occasional foot traffic and can be used between stepping stones along garden paths. Thyme also can be used as an edging or border plant in herb gardens.

The flavor of thyme blends well with lemon, garlic, and basil. Fresh or dried leaves can be used in cooking. Thyme often is used in marinades, meat dishes, casseroles, stews, herb butters, and vegetable dishes. The dried leaves and flowers of thyme can be used in sachets, and the essential oil of the herb is used in making colognes, soaps, and lotions.

Species

Many species, hybrids, and cultivars of thyme are available. Listed below are some of the most common plants used in home landscapes and their characteristics.

• T. vulgaris, common thyme - prostrate form, yellow and variegated foliage available, used in cooking.
• T. serphyllum, wild thyme - prostrate and upright forms, cultivars provide flower colors ranging from red to purple, foliage can be green, gold, or variegated.
• T. x. citriodorus, lemon thyme - upright form, golden and variegated silver foliage available, strong lemon scent.
• T. pseudolanuginosus, wooly thyme - prostrate form, pubescent stems and leaves appear gray in color, good for rock gardens.
• T. praecox, creeping thyme - mat-forming, grows only two to three inches tall, mauve, white, and crimson flowering cultivars available.

Planting thyme is an easy way to add fragrance and color to the garden. This easy-to-grow groundcover is an attractive addition to many landscapes.

This article originally appeared in the 8/13/2004 issue.