Leaves needle-like or scale-like, often evergreen.
1. Leaves in clusters of 2 or more.
2. Leaves in clusters of 10 or more, falling off during autumn.
3. Leaves blue-green; cone-scales smooth _Larix laricina_
3. Leaves bright green; cone-scales hairy _Larix decidua_
2. Leaves in clusters of 2-5, evergreen.
4. Leaves in clusters of 5 _Pinus strobus_
4. Leaves in clusters of 2-3.
5. Leaves in clusters of 2.
6. Most or all the leaves less than 3 inches long, usually
twisted.
7. Leaves up to 1½ inches long; sheath at base of leaves not
longer than ⅛ inch _Pinus banksiana_
7. Leaves 2-3 inches long; sheath at base of leaves at least
⅓ inch long _Pinus sylvestris_
6. Most or all the leaves longer than 3 inches, rarely
twisted.
8. Leaves mostly less than 5 inches long; cone-scale with a
small spine _Pinus echinata_
8. Leaves mostly more than 5 inches long; cone-scale without
a spine _Pinus resinosa_
5. Leaves in clusters of 3.
9. Leaves flexible, mostly less than 5 inches long; sheath at
base of leaves about ¼ inch long _Pinus echinata_
9. Leaves stiff, mostly more than 5 inches long; sheath at
base of leaves about 1 inch long _Pinus taeda_
1. Leaves solitary.
10. Leaves evergreen, of 2 types, some of them scale-like and about
⅛ inch long, some of them needle-like and up to ⅓ inch long
_Juniperus virginiana_
10. Leaves falling off in autumn, all needle-like, usually at least
½ inch long.
11. Leaves 3-angled.
12. Leaves blue-green _Larix laricina_
12. Leaves bright green _Larix decidua_
11. Leaves flat _Taxodium distichum_