Field studies were conducted in Upland and Pima cotton in the San Joaquin Valley (SJV) of California to evaluate the variability of upper canopy internode distances as a tool for estimating the need for the growth regulator mepiquat chloride. Data collected in both types of cotton showed significant differences in internode distances with node location and growth stage, and across field areas differing in plant vigor. This approach provided a useful tool for deciding mepiquat chloride application rates across a broader time frame than current University of CA Mepiquat Chloride guidelines for Acala varieties. This research has not established, however, impacts of changes in recommended rates and timing on vegetative growth control or yield in SJV cotton.