Novel Ethephon Application Methods for Narcissus

Abstract

Ethephon [(2-chloroethyl) phosphonic acid] is a plant growth regulator (PGR) that releases ethylene following application. Although ethephon is commonly used as a foliar spray during the commercial production of ornamental crops, including spring bulb crops such as daffodil (Narcissus pseudonarcissus L.), there has been increased interest in using ethephon as a root-zone-applied PGR. In this work, we evaluated a number of factors important for the development of ethephon as a soil drench for daffodil. Results indicate that a given dose (milligrams ethephon per pot) could be applied in volumes ranging from 15 to 120 mL (per 15-cm pot) with equal efficacy. Similarly, the same dose of ethephon could be applied as a foliar/substrate surface spray with volume of 105 to 525 mL·m−2 with equal efficacy. Although the efficacy of ethephon drenches interacted with forcing temperature, drenches were nonetheless effective across the range of temperatures commonly used for daffodil production. Plant size at the time of ethephon application had no effect on final plant size (at flower senescence). The rate of ethylene release from a peat-based substrate was highly temperature dependent, and ethephon was readily leached from this same substrate.