Empetrum nigrum (Black Crowberry)
|Also known as:|
|Life cycle:||perennial woody|
|Habitat:||part shade, sun; exposed bluffs, tundra, rock outcrops, boreal forest, sandy shores, bogs|
|Bloom season:||June - July|
|Plant height:||4 to 12 inches|
|Wetland Indicator Status:||GP: none MW: none NCNE: FAC|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Flowers are single in the upper leaf axils, with separate male and female flowers that may be on the same or separate plants; occasionally a flower may be perfect (with both male and female parts). Flowers are tiny and inconspicuous with 3 white petals that drop off early and 3 persistent pink to purple sepals. Female and perfect flowers have a 6 to 9-lobed ovary topped with a broad, saucer to funnel-shaped purple stigma with ragged edges.
Male and perfect flowers usually have 3 or 4 pink to purple stamens that are longer than the sepals. Flowers are very short-stalked.
Leaves and stems:
Leaves are alternate, spiraling around the stem and appearing whorled, leathery, evergreen, lance-linear to oblong-elliptic, up to about ¼ inch long (2.5 to 7 mm), toothless, hairless though may be minutely glandular, blunt at the tip, essentially stalkless, with a prominent midvein on the underside. Leaf edges are rolled under forming a psuedo groove on the underside and giving the appearance of a thick leaf. New leaves are mostly ascending, becoming widely spreading and eventually reflexed (downward pointing). Stems are woody, brown to reddish turning gray with age, many branched, creeping along the ground forming mats. Branches are mostly hairless though may be glandular and/or sparsely covered in matted white hairs near the tip.
Fruit is a round berry ¼ to 3/8 inch diameter that ripens to black. Inside are 6 to 9 seeds.
Black Crowberry is a low creeping shrub that can form large, dense mats and has a circumpolar distribution. It is very rare in Minnesota and possibly extirpated since, according to the DNR, it is only known from a single location—a small island in Lake Superior near Grand Portage—and the population found in 1929 has not (yet) been rediscovered. Elsewhere in the same group of islands is the related Purple Crowberry (Empetrum atropurpureum), which is similar in most respects except it has conspicuous matted hairs on branches and leaf edges, and mature fruit is purple. Both species are listed as Endangered in Minnesota due to their rarity. Some references consider the two to be different subspecies of E. nigrum (subsp. nigrum and hermaphroditum), and Flora of North American comments there is great variation within the Empetrum species and more research is needed, possibly separating North American species from those in Europe and Asia. Black Crowberry fruit is edible and has a long history of medicinal uses.
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Photos by John Thayer taken in Maine. Photos by Otto Gockman taken on Isle Royale, Michigan. Male flowers By Krzysztof Ziarnek, Kenraiz, via Wikimedia Commons, used under CC BY-SA 4.0
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