Juniperus communis L.
Common Name: COMMON JUNIPER, GROUND JUNIPER
Coefficient of Conservatism: 4
Coefficient of Wetness: 3
Wetness Index: FACU
Physiognomy: Nt Shrub

Most widespread on or near sandy shores and dunes along the Great Lakes, often associated with pines; also inland and there occurring in a diversity of habitats: old fields and gravelly banks, usually with scattered red-cedar in characteristic “juniper savannas;” also occasionally in coniferous swamps (on hummocks in wet places); in oak-hickory forests and northward scattered under jack pine and aspens; in the western Upper Peninsula in crevices of rock outcrops.

Our plants are almost all var. depressa Pursh, a ± decumbent form; the large cup- or saucer-shaped mats are characteristic of dunes and sandy places. However, several collections of upright, tree-like Juniperus from Alger, Antrim, Cheboygan, Emmet, and Montmorency Cos. are apparently J. communis var. communis, presumably spread from planted Juniperus of Eurasian origin. Various Old World forms of this species are cultivated for ornament. The Alger Co. collection notes a height of 8-10 m, though 4-5 m is more typical. The first collection of the var. communis was from Antrim Co. in 1953. 

Besides the growth form as small trees with upright trunks, the var. communis has longer needles, the longest 15-20 mm or more long in Michigan collections, and the glaucous central stomatal band occupies much of the needle width, being much wider (ca. 2-4 times) than the narrow green margin on either side of the needle. In the common spreading, shrubby var. depressa, the longest needles are less than 16 mm long even in shade forms, often only 6-10 mm in material from rocky shores, and the central stomatal band is narrower, usually 1.5 times or less as wide as the green margin on either side of the needle. See Adams, et al. (2016) for additional information.

Locations

Alcona County
Alger County
Allegan County
Alpena County
Antrim County
Arenac County
    Only on Charity Island
Barry County
Benzie County
Berrien County
Branch County
Calhoun County
Charlevoix County
    Including Beaver Island
Cheboygan County
Chippewa County
    Including Drummond Island
Clinton County
Delta County
Eaton County
Emmet County
Genesee County
Grand Traverse County
Gratiot County
Hillsdale County
Houghton County
Huron County
Ingham County
Iosco County
Iron County
Jackson County
Kalamazoo County
Keweenaw County
    Including Isle Royale
Leelanau County
    Including Fox Islands
    Including Manitou Islands
Lenawee County
Livingston County
Luce County
Mackinac County
    Including Bois Blanc, Mackinac, Round Islands
Manistee County
Marquette County
Mason County
Mecosta County
Menominee County
Montmorency County
Muskegon County
Newaygo County
Oakland County
Oceana County
Ogemaw County
Ontonagon County
Oscoda County
Ottawa County
Presque Isle County
Saginaw County
Schoolcraft County
St. Clair County
Van Buren County
Washtenaw County
Wayne County

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 14, 2017. http://michiganflora.net/species.aspx?id=887.