Thymus quinquecostatus aka Japanese Thyme

Thymus quinquecostatus is a low, creeping thyme with a woody base. It belongs to the mint family, Lamiaceae. Five-ribbed thyme is one of its common names. Its native range runs from Mongolia east to Japan. It also grows in China, Korea, and parts of Russia. In the wild, it grows on dry, rocky slopes and hillsides. Other sites include rock cracks, riverbanks, and dunes. It is a plant of temperate regions.

Creeping stems form a dense mat of small, scented leaves. Plants reach about 0.33–0.5 feet [0.10–0.15 metres] tall. Their spread reaches 1–2 feet [0.30–0.61 metres]. The blue-green leaves have an oblong to elliptic shape. Small oil glands dot their surfaces and hold the leaf scent. The stems can become woody with age. Trim them as needed to keep the mat neat. This also helps limit spread and bare, woody growth.

Flowers range from pale lilac to rose pink. They grow in short spikes above the leaf mat. Bloom lasts from July to August. The flowers add summer colour and draw butterflies. This low form suits herb beds and small patches of ground cover. It can fill gaps between stepping stones. Stems also spread across small rocks and trail over rock-garden ledges. The plant tolerates deer, dry soil, and shallow, stony ground.

Give this thyme full sun and soil that drains well. Loose, sandy or rocky soil suits it best. It grows in average soil and tolerates low soil fertility. Its water needs range from dry to moderate. It can withstand drought and needs little routine care. Missouri Botanical Garden lists it for USDA zones 5–8. The plant has no major insect or disease problems. Root rot remains a risk where wet soil drains poorly. Good drainage is therefore a key part of its care.

The leaves can flavour meat, fish, vegetables, soups, and stews. Harvest them at any time for kitchen use. Their flavour peaks in summer, just before the flowers open. For drying, gather leaves before bloom and dry them fast. The plant also supplies an essential oil used in food flavouring. Reported uses include perfume, deodorants, mouthwash, and antiseptic preparations. These uses do not establish the safety of home medicinal treatment. Plants For A Future lists no known hazards for this species. That statement does not confirm pet safety or safe essential-oil doses.