Growers commonly believe that lower corn (Zea mays L.) grain yields in no-till versus conventional-till systems are generally associated with reduced mean plant heights at critical stages throughout the growing season. However, mean plant heights may not be an accurate morphometric indicator or predictor of decreased grain yields in no-till corn. We hypothesize that: 1) no-till grain yield reductions, relative to those of conventional-till, are greatest when plant height variability is high, and 2) mean plant height is a poor indicator or predictor of grain yield response to tillage unless plant height variability is concomitantly large. The effect of plant height variability on mean grain yields was analyzed using 14 years of data involving a single hybrid, two crop rotations, and four tillage systems on a Chalmers silty clay loam. Throughout the 14 year study, plant heights were measured at 4 and 8 weeks after planting. No-till 4 and 8 week plant heights ranged from 73-132% and 59-120%, respectively, relative to conventional-till plant heights in the soybean-corn rotation, and from 39-112% and 45-100%, respectively, in the continuous corn rotation. Concurrently, no-till grain yields ranged from 76-106% relative to conventional-till grain yields when corn followed soybeans, and from 30-102% in continuous corn. Mean no-till grain yields were 96% and 81% of conventional-till yields in the soybean-corn and continuous corn rotations, respectively. Plant height variability generally varied with year, crop rotation, and tillage treatment, but tended to be highest in no-till, continuous corn cropping systems. Plant height variability may therefore be a more accurate indicator or predictor of no-till yield reductions than mean plant heights, especially in continuous corn rotations.