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 are even invasive on dunes and in sandy fields. Species spreading from cultivation in this area include Abies concolor, Larix decidua, Picea abies, P. pungens, several Pinus (P. nigra, P. ponderosa, P. rigida, P. sylvestris), and Pseudotsuga menziesii. Some of these also occur elsewhere in the State and some are known only from southwestern Michigan (as yet).

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.

Larix

2. Leaves evergreen, in clusters of (normally) 2 or 5; female cones more than 2 cm long.

Pinus

1. Leaves flattened or 4-sided, alternate (spiraled), borne singly, 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.

Abies

4. Terminal buds ± pointed, the scales evident, not enclosed in resin; scales persistent, the female cones pendant, remaining intact and eventually falling entire; undersides of leaves without whitish bands.

Pseudotsuga

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.

Tsuga

5. Leaves ± 4-sided, acute or sharp-pointed, sessile on the persistent peg-like base.

Picea