Our most diverse family of Conifers, especially important northwards. The "sand country" of southwestern Michigan, however, seems especially conducive to the spread of conifers from plantings, a few species of which even are invasive on dunes and in sandy fields.
1. Leaves needle-like, all or mostly grouped in definite clusters on short shoots.
2. Leaves deciduous, crowded and numerous on short lateral shoots (alternate leaves on new twigs); female cones less than 2 cm long.
2. Leaves evergreen, in clusters of (normally) 2 or 5; female cones more than 2 cm long.
1. Leaves flattened or 4-sided, alternate (spiraled), not in definite clusters.
3. Leaves persistent on dry branches, sessile, separating cleanly from an orbicular leaf-scar not or barely raised (on a low rounded ridge) above the surface of the twig.
4. Terminal buds rounded, densely covered in resin; female cones erect, the scales falling from the persistent central axis at maturity; underside of leaves with two whitish bands (formed by whitish stomata) on either side of the midvein.
4. Terminal buds ± pointed, the scales evident, not enclosed in resin; scales persistent, the female cones remaining intact, and eventually falling entire; undersides of leaves without whitish bands.
3. Leaves readily falling from dry branches, leaving persistent peg-like bases, the twig hence very rough.
5. Leaves flattened, rounded at apex, distinctly short-stalked in addition to the persistent narrow peg-like base.
5. Leaves ± 4-sided, acute or sharp-pointed, sessile on the persistent peg-like base.