Black Spruce

The Black Spruce (Picea mariana) is a common coniferous tree in North America. It is also known as Abies mariana, Picea brevifolia, Picea nigra, Pinus nigra

Natural hybridization between species of spruce is common. Although rare, Black and White Spruce hybrids, known as Rosendahl Spruce, have been found in northeastern Minnesota and other areas.

It differs from true firs, such as Balsam in having pendulous cones, persistent woody leaf-bases, and four-angled needles, scattered and pointing in every direction.

It differs from White Spruce, (Picea glauca), in having shorter needles, smaller and rounder cones, and a preference for wetter lowland areas.

It is a coniferous, slow-growing, small upright tree or dwarf shrub, having a straight trunk with little taper, and a narrow, pointed crown of short, compact, drooping branches with upturned tips. Through much of its range it averages 30'-50' with 6"-10" diameter at maturity. Growth varies with site conditions. In swamps it shows progressively slower growth rates from the edges toward the center.

The needles are 1/2" long, stiff, four-sided, dark bluish green and the bark is thin, scaly, and grayish brown. The roots are shallow and wide spreading with most in the upper 8" of organic soil. It is very susceptible to windthrow except in the densest stands.

The 0.6"-1.25" cones are the smallest of the spruces; nearly round, dull grey/black, in dense clusters in the upper crown, persisting for several years.

It is transcontinental in North America from Newfoundland to Alaska, south to British Columbia, Minnesota, and east to Rhode Island and Massachusetts.

It grows in both lowland and upland sites. In the southern portion of range it is found primarily on wet organic soils, but farther north its abundance on uplands increases. In the Lake States it is most abundant in peat bogs and swamps, also on transitional sites between peatlands and uplands. In these areas it is rare on uplands, except in isolated areas of northern Minnesota and the Upper Peninsula of Michigan.

Most stands are even-aged due to frequent fire intervals in Black Spruce forests. It commonly grows in pure stands on organic soils and in mixed stands on mineral soils. It is tolerant of nutrient-poor soils, and is commonly found on poorly drained acidic peatlands. It is considered a climax species over most of its range. However, some ecologists question whether Black Spruce forests truly attain climax because fires usually occur at 50-150 year intervals, while "stable" conditions may not be attained for several hundred years.

The frequent fire return interval perpetuates numerous successional communities. Throughout boreal North America, Paper Birch and Quaking Aspen are successional hardwoods that frequently invade burns in Black Spruce. Black Spruce typically seeds in promptly after fire, and with the continued absence of fire, will eventually dominate the hardwoods.

It is a pioneer that invades the sedge mat in filled-lake bogs, though often preceded slightly by Tamarack, with which it may in time form a stable forest cover in swamps. However, as the peat soil is gradually elevated by the accumulation of organic matter, and the fertility of the site improves, Balsam Fir and White Cedar will eventually replace Black Spruce and Tamarack.

The larvae of the Spruce Budworm moth cause defoliation and if it occurs several years in a row will lead to death, though Black Spruce is less susceptible than White Spruce, or Balsam Fir (Abies balsamea). Trees most at risk are those growing with Balsam Fir and White Spruce.