The leaves are needle-like, yellow-green, 12–15 mm (15⁄32–19⁄32 in) long, four-sided, curved, with a sharp point, and extend from all sides of the twig.

[20] Calcium concentration is important for red spruce for physiological processes such as dark respiration and cold tolerance, as well as disease resistance, signal transduction, membrane and cell wall synthesis and function, and regulation of stomata.

[21] During the 1980s, increased acid deposition contributed to a loss of high-elevation red spruce trees caused by leached calcium and thus decreased freezing tolerance.

[22] Additionally, the structure of the spruce needle enhances the capture of water and particles, which has been shown to add to soil acidification, nutrient leaching, and forest decline.

[23] However, more recently, reductions in acid deposition have contributed to red spruce resurgence in some mountain areas in the northeastern United States.

This suggests that policies aiming to reduce atmospheric pollution in this area have been effective, although other species sensitive to soil acidification, such as sugar maple, are still continuing to decline.

[22] The red spruce has low genetic diversity as well as a narrow ecological niche, meaning the tree is easily susceptible to changes within its environment.

In the late 19th and early 20th century, a vast amount of logging began in the state, and the number of red spruce dwindled to 12,000 hectares (30,000 acres).

[27] Significant efforts have been made to increase the growth of red spruce trees in western North Carolina, most notably by Molly Tartt on behalf of the Daughters of the American Revolution (DAR).