Analysis of petal extracts from various species revealed a wide range of lipoxygenase (LOX) activity among sources. A large increase in LOX activity was observed during senescence in both gladiolus (Gladiolus × hortulanus Bailey) and carnation (Dianthus caryophyllus L.) petal tissue. The increase began before the first visible signs of senescence were evident and activity peaked at early to mid-senescence stages. LOX activity of petal extracts from gladiolus was inhibited in vitro by phenidone, a known LOX inhibitor.