All plantains given potassium produced better yields than the control. The optimal dose was 300 g K per plant and when applied to plantains at about 19/20th leaf stage (4–5 months after planting) significantly (P = 0.05) increased the bunch weight (73.9%), number of marketable fungers (33.7%) and finger weight (44.2%) per plant over the control. The efficiency of fruit set also increased by over 10% while the time of harvest from planting was reduced by over 3 months. Super-optimal K applications significantly (P = 0.05) decreased the yield of plantains. However, the efficacy of suboptimal applications improved when applied about the 20th leaf stage. Potassium applications later than 20th leaf stage (five months after planting) did not increase the bunches developed. Although super-optimal doses cold be applied during the vegetative stage at about 15th leaf stage (approximately 3 months planting) to obtain high yield, such applications are wasteful. High yield of plantains usually associated with heavy potassium application 2–3 months after planting could also be achieved by timely application of smaller quantities of potassium at 19/20th leaf stages when platains need it most for floral initiation.