White & Black Spruce

  A stunted and windswept spruce just below the tree-line in the Mahoosuc Region

Seeing the Forest Through its Trees: Part VII

By Larry Ely

While red spruce is the most commonly found spruce species in the Mahoosuc Region (see Seeing the Forest Through its Trees Part VI), both black and white spruce are also found on sites where they are best adapted. A common name for black spruce is bog or swamp spruce, indicating where it might be found in the forested landscape. White spruce, sometimes called Canadian spruce, is most commonly a tree of the boreal forest more widely found in Canada than in the Mahoosucs where it reaches its most southern range. White spruce may grow on less preferred sites, but it is best suited to richer, better drained soils unlike our typical nutrient poor and rocky soils better suited to red spruce.

“Spruce grouse rely upon black and red spruce for their primary food source.”

Both black spruce and white spruce are transcontinental species with white spruce being hardy and thriving in long, cold winters and short, cool summers. Black spruce dominates in the krummholz in the Mahoosucs where trees are stunted and windswept just below tree-line, as well as along the edges of lower swamps and bogs. It also develops in the shallow bedrock depressions on open balds and can spread from rootings of its lower branches below snow and ice, often resulting in a prostrate mat. That ability to spread vegetatively through its roots is important because of its infrequent cone crop.

 Black spruce's ability to spread vegetatively through its roots is important because of its infrequent cone crop.

The best way to differentiate between black, white, and red spruce is to crush the needles. White spruce, sometimes called “cat spruce,” has a skunk-like smell while black spruce has been described as having a fresh, woody and sweet scent typical of a Christmas tree. The scent of the crushed needles of red spruce is more citrus-like. The twigs of the white spruce are also hairless and smooth unlike the red and black spruce, and its cones are more cylindrical than black spruce spherical cones.

“From windswept krummholz to quiet bogs, white and black spruce tell the story of survival at the very edge of the boreal forest.”

While red and white spruce can reach 60 to 90 feet in height with a 2-foot diameter, black spruce might only reach 50 to 70 feet with a 6 to 12-inch diameter. A 6-foot black spruce might be over 100 years old, growing in harsh conditions. All three resinous spruce species are highly flammable, but only black spruce have cones that are triggered by fire to release seeds. All three species can be long-lived, reaching up to 250 to 400 years with red spruce living the longest.

  Canada jay perched high on a spruce along the Appalachian Trail.

Spruce is primarily valued today for lumber and pulp, though historical uses saw roots of the black and white spruce used to tie birch bark for canoes and the boiled branches of black spruce to make spruce beer. The first chewing gum to be sold commercially was made in Portland from black spruce in the mid-1800s. 

All three spruce species are valuable to wildlife, providing seeds and nesting sites to songbirds and dense thermal cover for deer and moose. The thick year-round foliage, often top to bottom, of red and white spruce provides critical protection to snowshoe hare and American marten. Spruce grouse also rely upon black and red spruce for its primary food source, and black spruce is important breeding habitat for both the spruce grouse and the Canada jay. 

This is part of a continuing series looking at the life of the common trees in our Mahoosuc Mountain Region.

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