His ability to talk to plants would likely make his adventures in Hogwarts more interesting. He could have the plants as allies. They might warn him of approaching danger, like when the bad guys are sneaking around the school grounds. It would also mean he could understand if a plant was in distress and needed help, which could lead him to uncover some dark magic being used on the plants, and in turn, on the school.
This ability would be a great asset. In Hogwarts, there are many areas filled with plants. If Harry could talk to them, he could get unique perspectives. The plants could tell him about the history of the places they grow in. Also, during tasks or challenges, like the Triwizard Tournament, plants could offer him assistance. For instance, a plant might tell him how to get through a maze by indicating the correct path or warning him about traps.
Well, it could give him an edge in Herbology class for sure. He might be able to communicate with dangerous plants and figure out how to handle them better. Maybe he could even discover some hidden secrets about certain plants that are important for his adventures. For example, a plant might tell him where a hidden passage is or give him a clue about a mystery he's trying to solve.