You can try a few things:

(1) Try going to Settings --> Battery Life, and toggling the button to "High Performance". This will try to increase your frame rate, if possible, at the expense of longer battery life. It may not work for all devices or if you have tons of objects saved up at garden.

(2) If you are hoarding loot bubbles, 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.