Petal abscission involves cell death and reactive oxygen species (ROS) accumulation in the cells at the base of petals. Visualizing changes in the properties of these cells is crucial for analyzing and understanding petal abscission, a trait with important implications, especially for ornamental flower crops. This protocol describes the guidelines, experimental setups, and conditions for visualizing cell death by trypan blue staining and ROS accumulation by 3,3′-diaminobenzidine (DAB) staining in petals. Additionally, it provides instructions for staining and sectioning the entire Arabidopsis thaliana flower to give an improved view of the cells crucial for abscission. This protocol can be used to study the mechanism of petal abscission, including temporal changes at the base of petals during abscission and comparisons with mutants. Although Arabidopsis thaliana and cherry (Prunus sp.) blossoms are used as examples here, this protocol can easily be adapted for other plant species.