Putting a bunch of flowers on a grave

This action is an innovation (bid’ah) and exaggeration about
the dead. It is similar to the actions of those who venerated the righteous
and made symbols (of the dead). There is the fear that this may, with the
passage of time, lead to building domes over their graves, seeking blessing
from them and taking them as gods alongside Allaah. So we must not do that,
in order to avoid the means that lead to shirk.