Lingonberry or cowberry

Vaccinium vitis-idaea spreads by underground stems to form dense clonal colonies. Slender and brittle roots grow from the underground stems. The stems are rounded in cross-section and grow from 10 to 40 cm (4 to 16 in) in height. Leaves grow alternately and are oval, 5–30 mm (0.2–1.2 in) long, with a slightly wavy margin, and sometimes with a notched tip.
Flowers

The flowers are bell-shaped, white to pale pink, 3–8 mm (0.1–0.3 in) long, and produced in the early summer.

The fruit is a red berry 6–10 mm (0.2–0.4 in) across, with an acidic taste, ripening in late summer to autumn