Wa alaikum assalam wa rahmatullahi wa barakatuh, I pray that you are in the best of health and faith, insha’Allah. It is permitted to put flowers on a grave.

Ibn ‘Abbas said, “The Prophet, may Allah bless him and grant him peace, passed by a garden in Madina or Makka and heard the voices of two people who were being tortured in their graves. The Prophet, may Allah bless him and grant him peace, remarked, ‘They are being tortured and are not being punished for anything very great.’

Then he said, ‘Rather one of them did not guard himself from urine and the other was involved in back-biting.’ Then he called for a leafless palm branch and broke it into two pieces and put one on each grave. He was asked, ‘Messenger of Allah, why did you do this?’ He said, ‘Perhaps their torture will be lightened for them for as long as these do not dry up – or until they dry up.’”[Bukhari]