Intellectual Horticulture?

What does John Thompson mean by “intellectual horticulture“?

It seemed like intellectual horticulture. Seeds of knowledge planted in fertile minds were given an opportunity to germinate in a nourishing environment. Like plants that open their flowers to the wind, seeds from their work at the Fellowship will spread to and grow in other minds. Wherever the careers of these scholars take them that knowledge, and the spirit of active inquiry, will continue advancing our understanding of the human-animal relationship.