Only Picea engelmannii var. engelmannii occurs in the flora. In Mexico the species is also represented by P . engelmannii var. mexicana (Martínez) R. J. Taylor & T. F. Patterson.
Although Picea engelmannii varies considerably over its broad distributional range, the variation is continuous, militating against recognition of multiple varieties (R.J. Taylor and T.F. Patterson 1980). In the northern part of its range, it hybridizes freely and completely intergrades with P . glauca , as noted above.