Pinus L.
Family: Pinaceae
Pinus image
Kenneth J. Sytsma  
Pinus = Leaves evergreen, needle-like, in fascicles of 2 to 5.
1.a. Leaves in fascicles of 5; female cones 10-25 cm, at least twice as long as wide.
Pinus strobus
1.b. Leaves in fascicles of 2; female cones < 10 cm, much less than twice as long as wide.
2.a. Leaves 8-15 cm, straight and not strongly spreading.
Pinus resinosa
2.b. Leaves 2 - 7.5 cm, twisted or spreading apart.
3.a. Twigs brown; upper bark brown; female cone bent apically.
Pinus banksiana
3.b. Twigs pale greenish yellow; upper bark orange; female cones± straight.
Pinus sylvestris