There are a few different names for the thing that waters plants, depending on what you're referring to:

* Watering can: This is the most common name for a handheld container used to pour water onto plants.

* Sprinkler: This is a device that distributes water over a larger area, often used for lawns or gardens.

* Hose: This is a flexible tube used to transport water from a source to a desired location, often used with a sprinkler.

* Irrigation system: This is a more complex system that automatically waters plants, often using underground pipes and sprinklers.

* Water: This is the actual substance used to water plants, though not a specific tool.

So, the best answer depends on the context!