
Flora of the Carolinas and Virginia, Working Draft of 1 January 1997 -- Gymnosperms Alan S. Weakley.
Copyright - Alan S. Weakley, 1998, 1999. All Rights Reserved.
Pinus Linnaeus (Pine)
References: Kral in FNA (1993), Duncan & Duncan (1988).
Note that young saplings generally have shorter needles than larger saplings and mature trees; measurements in the key are those of mature trees.
Main Key
1. Needles 5 in each bundle; each needle with 1 vascular bundle..... P. strobus
1. Needles 2-3 (-4) in each bundle; each needle with 2 vascular bundles.....2
2. Bracts and bud scales fimbriate; sheath more than 1.3 cm long; needles 20-50 cm long, in bundles of 3 (-4); twigs about 1 cm in diameter.....P. palustris
2. Bracts and bud scales entire or edged with hairs, but not fimbriate; sheath less than 1.5 cm long; needles 3-30 cm long, in bundles of 2-4; twigs less than 1 cm in diameter.....3
3. Needles in bundles of 3, or 2 and 3, or 3 and 4 (predominantly or at least substantially in 3's).....4
3. Needles in bundles of 2 only.....9
4. Needles in bundles of 2 and 3.....5
4. Needles in bundles of 3 (rarely with a few 2's), or 3 and 4.....7
5. Needles 3-7 cm long; prickles on cones 3-8 mm long, stout (more than 1 mm wide at base of prickle).....P. pungens
5. Needles 5-30 cm long; prickles on cones 1-3 mm long, slender (less than 1 mm wide at base of prickle).....6
7. Cones distinctly longer than broad when open or closed, 5-13 cm long; needles mostly (10-) 12-23 (-28) cm long, 0.7-1.5 mm wide; buds not resinous (or only slightly so); trunks not producing adventitious sprouts (epicormic sprouting).....P. taeda
7. Cones about as broad as long, 3-6 cm long; needles (4-) 7-16 (-20) cm long, 1.5-2.0 mm wide; buds resinous; trunks commonly producing adventitious sprouts (epicormic sprouting), especially in response to fire......8
8. Needles (10-) 16-20 (-21) cm long, persisting 3-4 years; cones serotinous; [trees of pocosins, savannas, and other wetlands of the Coastal Pain].....P. serotina
8. Needles (4-) 7-10 (-15) cm long, persisting only 2 years; cones opening at maturity, not serotinous; [trees of ridges, slopes, bottomlands, and bogs of the Mountains and Piedmont].....P. rigida
9. Needles stout, 1.5-2 mm wide.....10
9. Needles slender to somewhat stout, 0.5-1.2 mm wide.....11
10. Leaves 3-6 (-8) cm long; cones 6-9 cm long, each scale bearing a stout, woody spine; [native tree of the Mountains and upper Piedmont] P. pungens
10. Leaves 7-15 cm long; cones 4-6 cm long, each scale bearing a small depressed mucro; [introduced tree, usually planted only on Coastal Plain barrier islands] P. thunbergiana
11. Needles 10-17 cm long; branches brittle; spring shoots with a single node, with 1 whorl of branches; [trees of the north, sometimes planted in our mountains] P. resinosa
11. Needles 2-13 cm long; branches flexible; spring shoots usually with several nodes (several whorls of branches); [trees of various habitats].....12
12. Needles 2-8 cm long, generally twisted; cones opening at maturity, not serotinous, the scales bearing prominent, slender prickles 2-5 mm long P. virginiana
12. Needles 5-13 cm long, twisted or not; cones opening at maturity or serotinous, the scales bearing prominent, short, stout prickles or minute, deciduous prickles, and also with a faint to conspicuous horizontal ridge.....13
13. Anthers yellow; bark tight, closely ridged, not sloughing off, reminiscent of a hardwood; tip of seed cone scales with a faint horizontal ridge and a minute, deciduous prickle; [native trees of mesic to fairly wet, fertile soils] P. glabra
13. Anthers dark orange; bark flaky, the laminated layers sloughing off in a manner typical of a pine; tip of seed cone scales with a conspicuous horizontal ridge and a short, stout prickle; [non-native trees of xeric sands] P. clausa
Auxiliary Key to common pines of the Piedmont
1. Needles 12-25 cm long, predominantly in bundles of 3; winter buds more than 1 cm long; cones 6-15 cm long, falling soon after releasing seed; bark plates thick, without crater-like blisters.....P. taeda
1. Needles 2-13 cm long, predominantly in bundles of 2; winter buds less than 1 cm long; cones 3-7 cm long, persisting on trees for several years after releasing seed; bark plates thin, with or without crater-like blisters.....2
2. Needles 7-13 cm long, not twisted, or slightly so, in bundles of 2 (usually with some in bundles of 3), rather slender, less than 1.0 mm wide; bark plates mostly more than 4 cm wide, with crater-like blisters ca. 1 mm in diameter; winter buds not very resinous; 3-4 year-old twigs rough and flaking.....P. echinata
2. Needles 2-8 cm long, typically twisted, in bundles of 2, rather stout, often 1.0-1.2 mm wide; bark plates mostly about 2 cm wide, without crater-like blisters; winter buds very resinous; 3-4 year-old twigs smoothish to rough, but not flaking P. virginiana