For piping buttercream flowers, your buttercream needs to be the right consistency. Too cold and your piping tip will split the bag; too warm and it wont hold the petal shapes.

I often use the microwave on a defrost or low setting to bring my buttercream to piping consistency if it’s too cold and firm to use. It doesn’t happen very often, but if I go a little bit too far and make it too warm, I temper it like I do with chocolate, to bring it to the consistency I want for piping flowers. It doesn’t do any harm to the buttercream and it saves time putting it in the fridge to firm up!