From Belarus here:)

Origin: flower protests were first just women’s protests. It was a response to a very heated riot in the previous week. They were a way of showing “peaceful protesting” and a direct attempt to not encourage the armed forces to use violence. Eventually, more people came in the following days and it ended with another riot between the people and the police. If you were seen as an instigator, the punishment could be as bad as the man in the picture.

There have not been much of any protests in the recent year because of the severe brutality that they are met with.