In-row spacing is the main factor controlling tuber size. Optimum seed spacing is based on varietal characteristics and climactic conditions. Closer in-row spacing is used in seed production to maximize yield of the desirable, smaller tuber sizes. In-row spacing of 6-12" (15-30 cm) are recommended for seed production, depending on variety, irrigated or rain-fed production, area in which the potatoes are grown and other climactic conditions.