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Wisconsin Plant of the Week

Picea mariana (Mill.) B.S.P.

Pinaceae (Pine Family)

Common Name:

black spruce

11/26/2001

Black spruce is a slow growing native conifer of cool northern and boreal forests.  Wisconsin is the southern edge of its range where itís confined to the wet, nutrient-poor organic soils of bogs. Further north its abundance on upland soils and over shallow bedrock increases. Black spruce is a small tree, rarely over 15 m tall in Wisconsin, with shallow roots, a narrow pointed crown, and drooping branches with upturned ends.

Like all spruce, black spruce needles are four-sided, and attached by a short woody peg all around each twig. Black spruce twigs are hairy and needles are blue-green and 6 to 15 mm long.  Male and female cones flower in late May to early June. By September female cones ripen and are round, 2 -3 cm, and dark brown to black. White spruce (P. glauca) is the only other spruce native to Wisconsin. Its twigs are hairless, needles are longer and cones are larger, cylindrical and lighter brown in color.

In drier northern sites, where frequent fires occur, black spruce stands are even-aged.  In wetter areas, with fewer fires and mixed aged stands, the trees still exhibit fire adaptations. Cones grow in dense clusters in the upper crown thatís less likely to burn.  The cones remain on the tree partly closed and release seed even five years or more after the seed is mature. Most seed release occurs after a fire and annually in winter and spring.

Germination requires a moist but not saturated medium, such as feather and sphagnum mosses, and full sun with no competition since first year seedlings are only 3 cm tall. Vegetative reproduction occurs by layering lower branches as the moss layer accumulates. At the northern limit of its range, layering accounts for most black spruce reproduction. 

Black spruce is a pioneer species like tamarack, but persists longer than tamarack since it tolerates some shade.  In the absence of fire organic matter accumulates and, as the peat surface rises, black spruce is eventually replaced by balsam fir and white cedar.

  • Origin of the name: Picea, L. picis, pitch; mariana, of Maryland, in the broad sense meaning North America, since black spruce is not native as far south as Maryland
  • Range:  Across Canada to Alaska from the tree line, south with isolated patches to southern MN, WI, NJ.
  • WI Range:  Most common north of the Tension Zone, but occurs south to Dane and Ozaukee Counties
  • Common associates: tamarack, white cedar, leatherleaf
  • Wetland Indicator Status: FACW
  • Coefficient of Conservatism:  8 (WI), not listed (S&W), 6 (MI)
  • More info: Silvics of North America
     
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