"A Chain Reaction" 

Although a plant tamer could communicate with plants, just like a beast and monster tamer could communicate with beasts and monsters, it didn't mean those beasts and monsters would always be 'docile' to the tamers. 

In most cases, beasts and monsters were actually more repulsive and aggressive in front of tamers because they could feel the sense of oppression and threat brought by the taming ability. 

Taming monsters and beasts always required forces and tamers always had this kind of natural deterrence that could subdue beasts and monsters. 

To be honest, without the ability to make contracts with beasts and monsters, tamers would also be helpless in front of these wild lives. 

The plants were generally more docile and friendly to plant tamers because instead of feeling threatened, plant tamers were regarded as one of a kind or friends.