Public posts on your Google+ stream are visible to:
- all users in your circles
- other users you have never interacted with
- anonymous users who don’t even have accounts
- Who can see your posts
- When you post publicly, people who’ve added you to one of their circles will see your update on their Home page. Your public posts will be displayed on the Posts tab of your profile and are viewable by anyone who wishes to see them. They also may appear in search results.
It is not necessary to add people to circles if you want them to see posts marked “Public”.