- Written also: Thymeleaf Speedwell
- Family: Plantain Family – Plantaginaceae
(formerly Figwort Family – Scrophulariaceae)
- Growing form: Perennial herb.
- Height: 5–20 cm (2–8 in.). Stem ascending, sometimes limp, glabrous or hairy (ssp. humifusa).
- Flower: Corolla almost regular (actinomorphic), white–pale blue and dark-striped, sometimes blue, 6–8 mm (0.24–0.32 in. (sometimes up to 10 mm (0.4 in.)) broad, fused, 4-lobed, wheel-shaped, short-tubed. Calyx 4-lobed, lobes glabrous. Stamens 2. Pistil a fused carpel. Inflorescence a terminal raceme. Flower-stalk shorter than subtending bracts.
- Leaves: Opposite, short-stalked. Leaf blade ovate–elliptic, with almost entire margins–shallow-toothed, glabrous or hairy.
- Fruit: Obcordate capsule, flat, 4–5 mm (0.16–0.2 in.) long, at most same length as calyx, broader than long, hairy.
- Habitat: Fields, damp meadows, pastures, lawns, roadsides, waste ground, ditches, shores, springs.
- Flowering time: (May–)June–August.
Thyme-leaved speedwell thrives in quite open places because it cannot stand very aggressive competition. It often grows on arable land, in yards and other places around people. It prefers ditch banks, shores and damp paths, especially with clay soil.
Thyme-leaved speedwell has been divided into two subspecies. In southern parts of Finland the common type species (ssp. serpyllifolia) has leaves with tapering tips, a white flower 4–7 mm (0.16–0.28 in.) across, and its flower-stalks are shortly white-haired. Before he became a famous preacher, Lars Laevi Laestadius described a new subspecies of thyme-leaved speedwell as a young botanist. Its leaves are quite blunt-tipped, its blue flower is 7–10 mm (0.28–0.4 in.) across, and the flower-stalks have dense brown, glandular hairs. It was later noticed that botanists had described the same subspecies twice in different parts of Europe, and according to the international rules the first name takes priority, so in this case the Scottish botanist Alexander Dickson’s name (ssp. humifusa) became official. In Finland ssp. humifusa grows rarely in quite a small area in north-east Lapland, where its bright blue flowers might catch the eye of a lucky traveller or eager botanist. Intermediate forms are also common.