Pinus glabra, the spruce pine, is a tree found on the coastal plains of the southern United States, from southern South Carolina south to northern Florida and west to southern Louisiana. This pine is a straight-growing, medium-sized species, attaining heights of 20–40 m.
The leaves are needle-like, in bundles of two, 5–8 cm long, slender (1 mm thick), and glossy dark green. The small, slender cones are 4–6 cm long, with weak prickles on the scales that are soon shed.
Pinus glabra differs markedly from most other pines in that it does not occur in largely pure pine forests, but is typically found as scattered trees in moist woodland habitats in mixed hardwood forest. To be able to compete successfully in such habitats, it has adapted to greater shade tolerance than most other pines.
Trees up to 30 m tall and 100 cm dbh. Trunk can be straight, but is often bent and twisted on trees that have regenerated beneath a canopy. Crown pyramidal to rounded. Bark on mature trees gray, fissured and cross-checked into elongate, irregular, scaly plates, lacking resin pockets; it resembles red oak bark, and is unlike any other pine in the region.
On younger trees and branches, the bark is smooth and gray. Branches whorled, spreading to ascending; twigs slender, purple-red to red-brown, occasionally glaucous, aging gray, smooth. Buds ovoid to ovoid-cylindric, red-brown, ca. 0.5-1 cm, slightly resinous; scale margins finely fringed. Leaves 2 per fascicle, spreading to ascending, persisting 2-3 years, 4-8(10) cm × 0.7-1.2 mm, straight, slightly twisted, dark green, stomata in lines on all surfaces, margins finely serrulate, apex acute; fascicle sheath 0.5-1 cm, base persistent.
