Hello Tim! Even though Apple set the characteristic Sprinkler years ago (https://www.apple.com/ios/home/accessories/) you still need a little help from the app Eve as Home does not allow to set a screen for Eve Aqua. Open the app Eve and goto Automations > Scenes and add a scene for watering. Once done it will be available in the app Home and you can set automations there using the scene with a trigger of your choice.
The function schedule in Eve is can addition/optional solution but only available in Eve.
Best regards, Volker
Aug 29, 2022