Empetrum nigrum

(black crowberry)

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Photo of Empetrum nigrum by Carl Roland

                            Synonyms
                            Species Description
                            Phenology
                            Reproduction
                            Insects/Disease/Pathogens
                            Known Uses/Ethnobotany
                            Species Distribution
                            Altitudinal/Topographic
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                            Community Ecology
                        

Empetrum nigrum (crowberry) is a perennial, dwarf shrub with needle-like leaves and shiny black berries, and the only member of its family (Empetraceae) in our flora. Its stems are extensively branched, growing in loose to dense mats, 1-5 mm broad, terete, grey when older and reddish yellow when young. The leaves are evergreen, needle-like, whorled, and up to 7 mm long. Two to three inconspicuous purplish-brown flowers appear in the leaf axils shortly after snow melt. The flowers are comprised of three scale-like bracts, three sepals, and usually three purple, 3 mm long petals. The fruits are black, globular, fleshy drupes, up to 9 mm in diameter with 2-9 white seeds. Stamens often remain on the fruit, indicating that the flower was bisexual (and hence the name E. nigrum ssp. hermaphroditum). The common name, crowberry, in Norse is 'Kraekling', referring to the unpalatable berries suitable only for crakes or crows (Dean and Bignall 2014). The only other black-berried plant in Denali, alpine bearberry (Arctostaphylos alpina), has large, net-veined leaves, not needle-like leaves.

Black crowberry flowers early, just after snow melt. Berries can be found in early June.

Empetrum nigrum is usually dioecious, with male and female flowers produced on separate plants. Some plants do have bisexual flowers, but these are not self-fertile. Fruits are juicy black berries, which are eaten by birds, bears and other animals, dispersing the seeds. The dioecious form of black crowberry requires both male and female plants in close vicinity to be pollinated by wind, bees, flies or lepidoptera (Aiken et al. 2003, Flora of Svalbard 2015). Plants also reproduce vegetatively by layering and by shoots.

The Database of Insects and Food Plants reports 20 insects that feed either as larvae or as adults on the leaves or flowers of Empetrum nigrum. Thirteen of these are macro-moths (Lepidoptera), one of these (Paradiarsia glareosa) oviposits on the leaves, another (Prolita sexpunctella) creates webs on the leaves, Glacies coracina feeds only on black crowberry, and a third (Zygaena exulans), feeds on unripe berries and shoots. The larvae of the butterfly, Callophrys rubi feed on the flowers and leaves of crowberry, as do the larvae of two aphid species, a ground bug, Eremocoris fenestratus, and two beetles (Altica britteni and Lochmaea caprea). The mite, Aceria empetri forms galls on the leaves of crowberry; the larvae and adults feed on the flowers and leaves. The Ecological Flora of the British Isles (2015) lists five micro-fungi associated with Empetrum nigrum: Arwidssonia empetri, Botryosphaeria, hyperborean, Chrysomyxa empetri, Phaeangellina empetri, and Physalospora empetri.

Black crowberry has been used as a food, dye plant, and medicinal. The berries, although not tasty when fresh, improve with cooking or preservation. The berries may have been an important survival food, especially when other berries were scare, since it is common in many plant communities, the berries form early, last throughout the winter, and preserve well. The Yup'ik commonly use these berries in akutaq ('Eskimo icecream'). Berries are also used as a dye for grass baskets (Jernigan et al. 2015). Recent research supports the use as a nutritive survival food. The berries contain glucose, fructose, inositol, galactose, and 33 different volatile compounds, 15 similar to those found in other blueberries (Kallio et al. 1984, Puntari et al. 1985, in Aiken et al. 2003). Thirteen anthocyanins have been identified in the berries, similar to those found in bilberry and blueberry (Ogawa 2008).

All parts of the plant have been used in traditional remedies, described in Moerman 1998, Garibaldi 1999, Foster and Hobbs 2002, Russell-Kari 1995, and Schofield 1989. The Inupiat and Athabascans of Alaska used the juice of the berries or a decoction of the stem bark to aid in the removal of cataracts and to relieve the pain of snow-blindness. The Athabascans made a decoction of the stem bark to treat upper respiratory conditions (colds, flu, cough, and chest congestion) and the Haida people of British Columbia used the same decoction to treat tuberculosis. The stem bark or cooked berries were used by the Athabascans to treat diarrhea, whereas the leaves with or without the berries were used as a laxative by the Haida, and a decoction of the green leaves was used as a purgative by the Bella Coola.

Disclaimer for Known Uses.

Empetrum nigrum is a circumpolar species. Crowberry occurs in Europe, Iceland, east to Siberia and Bulgaria, and in North America (Alaska, British Columbia, Yukon Territory, Northwest Territory, east to Newfoundland, south to New York, Minnesota and coastal northern California). The form with unisexual flowers and dioecious plants, Empetrum nigrum subsp. nigrum, occurs coastally in Alaska, whereas the form with bisexual flowers and monoecious plants E. nigrum subsp. hermaphroditum is more common in the interior especially with increasing elevation and latitude. Black crowberry is common and widespread throughout Denali on both sides of the Alaska Range crest.

Details are shown in the Plots & Charts found at right, depicting recent Denali data.

Empetrum nigrum occurs from 0-1900 m in North America. It is known from 156-1533 m in Denali and at an average of 757 m. It has the greatest cover in measured plots at 500-1100 m, increasing in frequency from 300 m to 1100 m. Approximately one-half (49%) of the 1753 measured occurrences are on slopes less than 5 degrees, the remaining are distributed almost equally between north and south facing slopes. Altitudinal distributions are similar for occurrences on both north and south facing slopes, as is the preference for altitudes 800-1100 m. The range of inclines (5-45 degrees) and majority of occurrences (10-20 degrees) is similar for north and south facing slopes. Black crowberry has the least amount of cover in plots with slopes greater than 28 degrees, decreasing in frequency with increasing inclination.

Details are shown in the Plots & Charts found at right. For more on how to interpret these figures, visit Understanding Data Presented.

Black crowberry is most often found in mesic, nitrogen poor, acidic soils, with a high organic layer in coastal areas and interior boreal montane tundra communities of Alaska and British Columbia (Klinka et al. 1989). It is also found on soils of low organic content and neutral to basic soil pH at higher latitudes and altitudes (Aiken et al. 2003, Flora of Svalbard 2016).

Wide-ranging, wet to somewhat dry sites.