A while ago I was reading a short story / novella, possibly part of an anthology. The Premise was: Human space explorers land on an alien world, and discovers a primitive species that is Stone Age in everything except for horticulture. This species was in fact, weirdly advanced, and weirdly obsessed over caring for their crops. Over time, the human explorers become increasingly worried, although nothing has posed any visible threat. At least one of the humans then figures out that the “crops” themselves are not only not native to the world they are on, but are also intelligent, and telepathic; and that they somehow came to this world long ago, and enslaved the evolving sentient natives to care for them.
This revelation creates a panic among the humans, who begin to fight among themselves on how to solve it. Several decide they should send a signal to earth to stay away, and destroy their ship to prevent the plants from ever leaving that world. However, at least one human succumbs to the plants dominance, and flees with the ship home to “warn earth” never realizing that their own primitive “fight or flight” response had been hijacked by the plants, to trick them into carrying seeds home to earth for colonization.