Hybrid white Cattleya Louise Georgeianna orchids were purchased from a nearby commercial greenhouse grower. Upon delivery, the bare rooted plants were immediately potted in 100% medium grade Douglas fir bark in 17.6-cm plastic pots, watered with tap water, and placed in an environmental growth room (27-C day, 21-C night; 1400 ft-c; 16-hr photoperiod; 62 to 68% relative humidity). About 3 days prior to flower scape emergence from the sheath, the entire plant was treated once each day with 750 mg/liter of AgNO3 containing 0.01% Tween 20 as a surfactant. As soon as the flower scape emerged from the sheath, the AgNO3 concentration was dropped to 10 mg/liter to avoid injury to the delicate sepals. The entire flower scape was sprayed to run off each day with this reduced amount of AgNO3 until the individual flowers were fully open. This generally required 2 to 3 days. Then, both control (solvent-treated) and treated plants with fully opened flowers were placed in a large chamber in the laboratory and exposed to 0.2 A1/liter of ethylene for 24 hr. Plants were then returned to the environmental growth room and observed daily. It was necessary to expose the flowers to ethylene shortly after they had fully opened since 3 to 5 days later, flower hardening had occurred which greatly reduced their sensitivity to ethylene.