Disclosed are methods of enhancing plant growth, comprising treating seed at least one month prior to planting with an effective amount of a plant signal molecule, 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, compared to plants harvested from untreated seed, or compared to plants harvested from seed treated with the signal molecule just prior to or within a week or less of planting.