The rapid grass growth at the start of the game is just syncing up the grass growth. To speed up the syncing, use Turbo Mode. Watch the project to make grass grow. The grass' growth is stored on the cloud, so whenever someone watches the project, the grass grows for everyone. New Scratchers and people not signed in can't contribute to global grass growth due to how Scratch works,
Won the "Most Realistic Game Award 2018" and "Most Exciting Action Game of the 21st Century"*, this game is fun for the whole family. *unconfirmed