Empetrum nigrum

Empetrum nigrum, also known as Black Crowberry, is an evergreen undershrub native to northerly mountain regions, and is relatively unknown to gardeners. This cousin of heathers produces small pink flowers in summer, followed by black and edible berries resembling blueberries on the female plants, which can be harvested in September. To successfully grow this ground cover plant, provide it with sunshine and light soil that is preferably moist. In the garden, it will thrive near water sources, in borders, or in damp rockeries, preferably in acidic soil. To achieve fruiting, it is necessary to plant at least one male and one female plant.

Empetrum nigrum belongs to the heath family. It is native to Northern Europe, Central Europe, Siberia, Japan, and the northern part of the American continent. In the wild, this species grows in heathlands and marshes, in lowland areas under the coldest climates, and takes refuge in high mountainous areas everywhere else. 

This is a relatively slow-growing undershrub, with a spread-out habit forming a wide ground cover cushion. When fully grown, it will not exceed 25-30 cm (9.8-11.8 in) in height with a diameter of 50 cm. The vegetation of this plant consists of reddish and prostrate stems capable of rooting upon contact with the ground, and straightening at their tips. The stems are densely covered with small, very narrow, and leathery leaves: linear in shape, they are rolled upon themselves and measure 4 to 6 mm (0.2 to 0.2 in) in length and 1 to 2 mm (0 to 0.1 in) in width. Their colour is dark green. The quite discreet flowering, takes place in summer, usually in June-July. The tiny flowers, measuring 1 to 2 mm (0 to 0.1 in) in diameter with 6 petals, are pink to purple-pink. In this dioecious plant, there are male and female individuals. Only the females will produce fruits that ripen in September. These beautiful berries are fleshy, sweet, and delicious: in Iceland, they are commonly used in delicious jams and to garnish succulent pies.

The Black Crowberry is one of those modest shrubs requiring very little maintenance in favourable climate and soil conditions, but providing a harvest of small fruits that are tasty and rich in vitamins, valuable for helping both young and old get through the winter. It is not difficult to find a place for it in the garden, and it is useful for covering the ground in inhospitable, peaty, or waterlogged areas. For example, several plants can be planted along a pathway, or a few individuals can be scattered in a rockery. It is an excellent companion for heathers, which will bring colour, and for other small undershrubs such as bugleweed or rockroses in well-drained soil.