Selection for straightness in natural stands of cottonwood can be effective in improving straightness of open-pollinated progeny. Straightness appears to be highly heritable, but it is subject to imprecise evaluation. This can be largely overcome by repeated application of an imprecise scoring system using a minimum of two views per tree separated by 90 degrees.
Cooper, D.T.; Ferguson, R.B. 1981. Evaluation of Bole Straightness in Cottonwood Using Visual Scores. Res. Note SO-277. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station. 3 p.