Empetrum nigrum

Empetrum nigrum is a low growing, evergreen shrub with a creeping habit.^[11] The leaves are 3–6 millimetres (1⁄8–1⁄4 inch) long, arranged alternately along the stem. The stems are red when young and then fade to brown; they grow slowly, around 7 – 15 cm (3 – 6 inches) per year^[12][13]. This plant can form thick, clonal mats than prevent other plants from overgrowing it.^[12]

Empetrum nigrum is usually dioecious, though a few individuals are bisexual and have perfect flowers^[14]. Because this species is highly clonal, an entire patch may be of a single sex. Empetrum nigrum flower buds start to develop the summer before they open^[13], blooming the following year between May and June.^[15] The flowers are small (3 – 6 mm), have little or no scent and are not very noticeable,^[11] Flowers consist of 3 greenish-pink sepals that turn reddish purple^[16], 3 petals, 3 stamens (males) or a pistil with an ovary that contains 6 – 9 ovules (females).^[17]

The round fruits are drupes, 4–6 mm (1⁄8–1⁄4 in) wide, usually black or purplish-black but occasionally red^[18] and contain an average of 7.8 seeds per fruit. The fruits are well-protected against pathogens^[19] and as a result can persist throughout the winter.^[20] Fruits average 86.5% water, and their dry weight includes 14.4% carbohydrates and 12.2% lipids, which is possibly the highest lipid content of any fleshy fruit in Europe.^[21]

• Empetrum nigrum subsp. asiaticum (Nakai ex H.Ito) Kuvaev – Korean crowberry^[22]
• Empetrum nigrum subsp. subholarcticum (V.N.Vassil.) Kuvaev (synonym: Empetrum subholarcticum V.N.Vassil.)^[23]

The species has a near circumboreal distribution in the Northern Hemisphere.^[24]

Empetrum nigrum grows in bogs^[25] and other acidic soils in shady, moist areas; it also grows in subalpine and alpine habitats in the Pacific Northwest. It can grow in soils with a pH as low as 2.5, but it does not grow in basic soils (pH > 8).^[26]

Empetrum nigrum flowers are likely pollinated by a combination of generalist insects (e.g., flies, beetles) and wind.^[4][12] Animals that regularly consume this species and act as seed dispersers include rodents,^[27] foxes, bears,^[28] caribou^[29] and many bird species.^[30] Because it retains its fruit throughout the winter and into the spring, it is an important food for species such as red-backed voles at a time of year when few other foods are available.^[20]

The moth species Glacies coracina, Zygaena exulans, and Hadula melanopa feed on the plant.^[15]

The metabolism and photosynthetic parameters of Empetrum can be altered in winter-warming experiments.^[31]

Empetrum nigrum has allelopathic properties (e.g. hampering seed germination and root extension of other plants) but the strength of these are dependent on the soil type.^[32]

Empetrum nigrum roots host ericoid mycorrhizal species (ascomycetes and basidiomycetes), which increase access to nitrogen and phosphorus.^[33]

The fruit is edible and can be dried,^[34] and may have an acidic taste. In the Alaskan tundra, it is known to have a sweet and slightly tart flavor. It is often mixed with other berries in dishes like pies and puddings.^[25]

It is abundant in Scandinavia and treasured for its ability to make liqueur, wine, juice, or jelly. In subarctic areas, the plant has been a vital addition to the diet of the Inuit and the Sami.^{[citation needed]} It is used to make Alaskan ice cream.^[25] The Dena'ina (Tanaina) harvest it for food, sometimes storing in quantity for winter, sometimes mixed with lard or oil.^{[citation needed]}

In the Canadian province of Newfoundland and Labrador, the berries (known locally as “blackberries”) are used in jams, jellies, and baked goods, such as buns, or puddings.^[35] In Labrador and northern regions of Newfoundland, entire plants are harvested and the sods used to impart flavour to smoked fish.^[36]

The species can also be grown as a ground cover,^[37] or as an ornamental plant in rock gardens, notably the yellow-foliaged cultivar 'Lucia'. The fruit is high in anthocyanin pigment and can be used to make a natural dye.^[37]

The Scottish Highlands Clan Maclean's badge is believed to be E. nigrum.^[38]