The maturity indices of percent fruit drop, percent soluble solids, and flesh firmness of apples from trees with `Starkspur Supreme' scions on nine rootstocks were compared over the five-year period 1985-1989. The nine rootstocks included EMLA 7, EMLA 9, EMLA 26, EMLA 27, Mark, MAC 24, Ottawa 3, OAR 1, and M9.
The five-year averages of each of the maturity indices varied significantly among the nine stions. The average percent fruit drop was more strongly correlated with trunk cross-sectional area (r=0.572) than it was with cumulative yield efficiency (r=0.346). Flesh firmness was significantly correlated with cumulative yield efficiency (r=0.398) but not with either trunk cross-sectional area or cumulative yield. The average percent soluble solids was more significantly correlated with trunk cross-sectional area (r=0.770) than it was with either cumulative yield efficiency (r=0.383) or cumulative yield (r=0.637). It is suggested that tree size may be used as an indicator for predicting maturity in cases where little or no information is available on the effects of that particular rootstock on maturity.