Empetrum is a genus of three species of dwarf, evergreen shrubs in the heath family Ericaceae, order Ericales. Commonly known as crowberries, they are low, mat-forming plants with slender, wiry, spreading branches and small needle-like leaves 3–10 mm long. The leaf margins are recurved, forming a hollow cylinder that encloses the hairy underside of the leaf — an adaptation that limits water loss and allows the plants to thrive in exposed, often desiccating habitats. Flowers are small and either bisexual or dioecious; the fruit is a fairly dry berry that ripens to black, red, or deep purple depending on species.
The genus was long placed in its own family Empetraceae alongside the related genera Ceratiola and Corema, but molecular and morphological evidence now unites all three within Ericaceae, specifically as a tribe in the subfamily Ericoideae. The tribe shares a suite of distinctive features considered adaptations to wind pollination.
The three recognized species are Empetrum nigrum (black crowberry, circumpolar in the Northern Hemisphere), E. rubrum (red crowberry, South America and sub-Antarctic islands), and E. eamesii (pink crowberry, northeastern North America). The genus displays a striking bipolar distribution — Northern Hemisphere tundra and moorland populations are separated from disjunct Southern Hemisphere populations in the Andes and sub-Antarctic islands including South Georgia, the Falkland Islands, and Tristan da Cunha. Evolutionary biologists attribute this gap-bridging distribution to long-distance seed dispersal by migratory birds.
Crowberries grow in moorlands, tundra, muskeg, boreal spruce forest, and coastal sand dunes. Their berries have been an important food source for Inuit and Sami peoples, and are still harvested today. The high anthocyanin content gives the berries potential as a natural food dye.
Etymology
The genus name Empetrum derives from the Greek en (“on”) and petra (“rock”), referring to the rocky, exposed habitats where these plants characteristically grow.
Distribution
Empetrum species occur across the Northern Hemisphere from temperate to subarctic climates, with a disjunct presence in the Southern Andes, the Falkland Islands, South Georgia, and Tristan da Cunha. The typical habitat is moorland, tundra, muskeg, and boreal forest, as well as coastal dunes and dune slacks. The bipolar distribution is thought to result from seed dispersal by long-distance migratory birds.
Ecology
Plants grow in open, often windswept habitats including tundra, moorland, muskeg, boreal spruce forest, and coastal dune systems. Their leaf anatomy — recurved margins concealing the hairy underside — reduces water loss and suits them to exposed, dry-wind conditions. The genus is wind-pollinated, and the tribe to which it belongs within Ericaceae shows a suite of morphological features associated with anemophily. Berries are consumed and dispersed by birds, including migratory species responsible for the genus’s bipolar range.
Cultural Uses
Crowberry fruits have been a significant wild food for circumpolar Indigenous peoples, particularly the Inuit and Sami, who gather them in late summer and autumn and store them for winter use. The Dena’ina (Tanaina) of Alaska eat the berries fresh or mixed with lard or oil, and also use the leaves, stems, and roots medicinally — infusions are taken for diarrhea and stomach complaints, and a root tea is applied as an eye wash. The high anthocyanin pigment in the fruit can be used as a natural food dye, and the berries are suitable for pies and jellies.
Taxonomy Notes
For most of the 20th century Empetrum, Ceratiola, and Corema were placed in the segregate family Empetraceae. Molecular phylogenetic data, together with leaf morphology and other evidence, now firmly place the group within Ericaceae as a tribe in the subfamily Ericoideae. The current GBIF backbone places Empetrum in the order Ericales, family Ericaceae. The tribe retains a number of distinctive morphological features associated with wind pollination that distinguish it from most other Ericaceae.
Cultivation
Crowberries are occasionally cultivated as ornamental ground cover in rockeries and heath gardens. Empetrum nigrum ‘Lucia’, a cultivar with yellow foliage, is among the named selections grown for ornamental purposes. Plants prefer acidic, well-drained soils and cool climates in line with their natural moorland and tundra habitats.
