This largely Appalachian species is often hard to distinguish from the more southern echinata. Reports of rigida from west of the Appalachian Plateaus are not mapped here, pending verification (Gm, CW); Gm reported this species west along the Knobs as far as BULL (Gm). On the Cumberland Plateau, it extends south to near the state line, but perhaps not into Tenn. (Ch, K). P. rigida differs from echinata (F, Cr, FNA 2, J) in its generally broader seed-cones (ca. 4-8 x 6-7 cm versus 4-6 x 3-4 cm), the scales relatively thick, with distinct dark reddish-brown inner distal margins (versus lacking contrast), the terminal prickle up to 3 mm (versus 2 mm), more slender and downcurved. Its needles are relatively rigid, ca. 1-1.5 (2) mm wide (versus 0.7-1.3 mm), clearly twisted (versus slightly to not at all), mostly in bundles of 3 or rarely 5 (versus 2 or rarely 3), and relatively deep green (versus blue-greyish); twigs are initially orange-brown (versus greenish to reddish-brown and often glaucous-covered), becoming ca. 5-7 mm thick in second year (versus 3-5 mm), with strongly resinous buds ca. 1-1.5 cm long (versus 0.7-1 cm); bark plates lack resin pockets (as usually evident in echinata). The state champion is reported from MAGO (KDF 2020): 133 cm dbh, 27 m tall, 21 m wide.