[This is the T-rated version, for those who would prefer something SFW]
Here's a silly pic I made involving a few Vinecer tourists, with one flirting with another.
During the mating season, around late autumn and early winter, Vinecers start to produce an aromatic pheromone. When ready to mate, one would release this into the air to let others know and to attract Vinecers who were also ready. These pheromones aren't used as much after finding a partner. Single Vinecers sometimes use them when flirting. These pheromones gradually stimulate sexual arousement, and prolonged exposure to them will cause a Vinecer to get horny.