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Picea rubens Sarg. Red spruce
Habitat
Red spruce occurs on well-drained sites in lowland and upland areas. It is a very shade-tolerant species that may be found in mixture with many species—for example, as an understorey species growing beneath aspens and birches, as a companion species with balsam fir, eastern hemlock, and eastern white pine, and as a lesser component with sugar maple and beech. It is the predominant spruce species in western and central New Brunswick.
Form
Red spruce grows to heights of up to 26 m and to stem diameters of up to 60 cm. The crown is conical when young. It becomes broadly conical in older trees and is made up of rather thinly foliated branches that are mostly horizontal and upturned at their ends. This gives a pagoda-like appearance to the crown which, in stand-grown situations, occupies no more than about one-third of the height of the tree.
Morphology
The leaves are needle like, 7–16 mm long, roundly four-sided, bluntly tipped, and shiny, yellowish green. Each is borne on a brownish pulvinus, or leaf cushion, that projects from the shoot. The leaves occur in a series of long spirals around the shoot and tend to lie somewhat forward, or appressed, along the shoot with those attached on the underside being bent upwards a little.
The twig surfaces are made up of longitudinally arranged, small, round-topped ridges, each of which supports near its outer end a leaf cushion with its leaf. The twig surfaces become pale orange brown by the end of the growing season. The round- topped ridges carry a few tiny steeple-shaped hairs on their surfaces, and many more in the valleys between the ridges. The terminal bud is surrounded by small, forward-pointing leaves that tend to obscure it. The bud has shiny, reddish-brown outer scales that sometimes extend slightly. Smaller, ovoid, lateral buds may occur in axils of leaves farther back along the shoot.
Pollen cones and seed cones extend from their buds before the new shoots begin to grow. Pollen cones grow erect to lengths of 12–18 mm, shed their pollen into the air, and then shrivel and later drop from the tree. The young seed cones also grow erect at first, when their pinkish- purple scales are spread apart to channel pollen in to where the ovules are. Then the scales close up, or are pressed together as the cones grow, turn downwards, reach full size by mid-July, and mature. The ripe reddish-brown, 25- to 40-mm long, ovoid, pendant, cones spread their dry scales apart to release their seeds, starting in about mid- September.
The bark of young trees is pale reddish brown and loosely scaled, or shreddy. On older trees, the bark is broken into elongatedreddish-brown to reddish-blackscales with, ultimately, deep furrows. From a distance, the trunks of red spruce trees show up because they have a distinct purplish hue which, once recognized, is a valuable feature for identification.
Notes
Some people may have difficulty distinguishing the three spruce species native to New Brunswick. They each have distinct features.
White spruce (Picea glauca (Moench) Voss) can have a similar stature and crown breadth to red spruce, but its crown is usually bushier in appearance because its branches are more heavily foliated and do not tend to turn up much at their ends. The crown is also often spread farther down the stem. From a distance, the crown is bluish green, not yellowish green as is that of red spruce. At the shoot level, the bluish-green leaves are longer than those of red spruce and are spread outward around the shoot. Leaves are more pointed and, along the twig surfaces, the rounded ridges usually bear no hairs. The mature seed cones are more cylindrical than those of red spruce, and are softer to the touch, being less woody. The bark of white spruce is relatively smooth and grey until old age when it darkens and becomes more scaly.
Shoot surface showing its round-surfaced ridges that carry the leaf cushions and steeple-shaped hairs
Black spruce (Picea mariana (Mill.) B.S.P.) has a narrower crown than the other two spruces. The top of its crown is often densely tufted because it carries a mass of short branches and cones and, below the middle, branches tend to droop downwards in open conditions, sometimes to the ground. Like those of white spruce, its leaves are bluish green, but usually more distinctly whitish blue on their undersurfaces. They are of similar size to those of red spruce and may be somewhat appressed to the shoot or more spreading. The leaf cushions are attached to flat-surfaced ridges, so the surface of a black spruce shoot resembles more the staves of a barrel than the fingers on the back of a hand, as do those of red and white spruce. Both the flat surfaces and the indentations between them are covered with short hairs, many of which have tiny swollen glands at their ends, so they look like little straight pins; some are curled in various ways. Black spruce seed cones are darker, smaller, and more orbicular than those of red spruce. Most stay unopened on the trees for many years but some, especially on younger trees, do open somewhat during their first fall. The bark of black spruce is dark and scaly.
Twig-surface features and leaves offer the simplest and surest way to dinstinguish the three species. The ridge and hair features (which require a hand lens for proper viewing), and the leaf color and orientation, readily combine for positive identification. The best shoots to use are side shoots at the end of a branch, and the easiest viewing is of the undersurfaces of the shoots.
Red spruce and black spruce hybridize with each other when they grow in close proximity, and their offspring can cross back with either parent. As this sort of introgressive hybridization goes on over time, populations can arise in which individual trees may be of all shades of mixture of the two species. This has happened in the plateau area of central New Brunswick where the typically upland red spruce grow on well-drained soils close to the typically lowland black spruce on poorly drained soils. Because there is only a few meters’ difference in elevation between the two types of sites, interbreeding has occurred and offspring have been able to establish on intermediate sites. Nevertheless, it is usually possible to identify hybrid individuals as “mostly black spruce” or “mostly red spruce.” The problem, however, is that gradually the species are becoming less and less pure. This is more of a concern for red spruce than for black spruce because it has a much smaller range and, in New Brunswick, the ranges of the two species overlap entirely.
Red spruce is likely to suffer severe defoliation by spruce budworm. This will particularly be the case when it is growing in mixture with balsam fir, which suffers more. Red spruce/black spruce hybrids suffer less than do red spruce trees, so in spruce budworm-killed areas some hybrids may survive. This also serves to “dilute” the red spruce population.
Red spruce wood is pale brown or cream, relatively soft, and moderately strong. It is used as lumber for construction, in plywood, and as a source of wood pulp.