Disclosed herein is a method of enhancing plant growth, comprising treating a seed at least one month prior to planting with a chitooligosaccharide (CO), such as those shown in the figures, wherein, upon harvesting, the plant exhibits at least one of increased plant yield measured in terms of bushels/acre, increased root number, increased root length, increased root mass, increased root volume and increased leaf area, as compared to a plant harvested from a control seed, optionally a control seed treated with the CO just prior to or within a week or less of planting.
