Disclosed herein are method of enhancing plant growth, comprising treating a plant seed and/or the plant that germinates from the seed with an effective amount of at least one chitoogilosaccharide (CO) less than one month prior to planting the seed and the seed is not also treated with a lipo-chitooligosaccharide (LCO). The treatment results in 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, compared to plants harvested from untreated seed.
