Abstract: Two experiments were conducted to understand the effect of light emitting diodes on postharvest abscission in balsam fir (Abies balsamea L.) branches. In one experiment, branches were pre-exposed to the fluorescent light, LEDs, or darkness for 1, 4, 8, 12, 24, or 48 h. In a second experiment, branches were constantly exposed to fluorescent lights, LEDs, or darkness. The response variable was needle retention duration (NRD). A 48-hour exposure time to red, white, or blue LEDs significantly (P < 0.001) increased NRD by approximately 75, 118, or 127%, respectively, compared to a cool white fluorescent lighting or darkness. Constant exposure to any LED significantly (P < 0.001) improved NRD compared to fluorescent lights or darkness, though white and red LEDs were most effective. It is speculated that LED-promoted needle retention could possibly be due to changes in carbohydrate synthesis similar to those observed during cold acclimation.