Our most diverse family of Conifers, especially important northwards where most species are capable of dominating specific habitats.
Many Pinaceae (and Cupressaceae) are also used for reforestation, including both native and alien species. Some of these are increasingly spreading in southern Michigan. The "sand country" of southwestern Michigan seems especially conducive to the spread of conifers from plantings, a few species of which even are invasive on dunes and in sandy fields. Conifers spreading from plantings have often been ignored by collectors, but we try to represent the situation in our species pages to both aid in knowing the native range of our native species and to track potentially invasive species such as Pinus nigra and P. sylvestris.
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.