Farms are symbols of growth. But they are also linked to growth on a major scale. They can link to thoughts and feelings and ways of thinking that we are trying to encourage in others. If you were trying to influence others and even teach them new ideas then that maybe what has triggered the dream. Farms may also be about us trying to develop ourselves and may link to people, ideas and places which are helping and encouraging our development. That development may not always be thought of as "good" as it can quite easily represent new bad habits and groups of people whom maybe leading us astray.
Growing plants, farming, or raising animals on a farm can represent a real-life activity where you invest time or resources for a long-term gain. For example, tending a farm (that you don't have in real life) could actually represent your real-life activity of managing your stock portfolio.