Narcissus response to plant growth regulators

Abstract

Three experiments were conducted to determine the effectiveness of plant growth regulators (PGRs) on 'Tete a Tete', 'Dutch Master', and 'Sweetness' narcissus (Narcissus pseudonarcissus). Ethephon foliar sprays (500 to 2500 mg·L-1) and substrate drenches of flurprimidol and paclobutrazol (0.25 to 4 mg/ pot a.i.) did not control height during greenhouse forcing of 'Tete a Tete' at any concentration trialed. Stem stretch was controlled during postharvest evaluation with ethephon foliar sprays ≥1000 mg·L-1, flurprimidol substrate drenches ≥0.5 mg/pot a.i., and paclobutrazol substrate drenches of 4 mg/pot a.i. A second experiment investigated preplant bulb soaks of flurprimidol (10 to 40 mg·L -1) applied to 'Dutch Master' and 'Tete a Tete' narcissus bulbs. Flurprimidol preplant bulb soaks controlled postharvest stretch on 'Tete a Tete' and 'Dutch Master' at concentrations ≥15 and ≥10 mg·L -1, respectively. A third experiment was conducted with paclobutrazol (75 to 375 mg·L-1) on 'Tete a Tete' and 'Dutch Master' and three concentrations of flurprimidol on 'Sweetness' to determine optimal soak recommendations. Paclobutrazol preplant bulb soaks ≥75 mg·L -1 controlled postharvest stretch of 'Tete a Tete' and 'Dutch Master', while 37.5 mg·L-1 of flurprimidol controlled postharvest stretch of 'Sweetness'. Based on the results of these experiments, growers can now select a PGR to help control excessive plant growth.