You can try a few things:
> (1) Try going to Settings --> Battery Life, and toggling the button to Battery Saver. This will try to slow your frame rate down, if possible, to save battery. It may not work for all devices.
> (2) If you are hoarding loot orbs, try to get rid of as many as possible. Having all of these extra objects around in garden can put extra strain on your processor and battery when you are playing in garden.