Ethephon [(2-chloroethyl) phosphonic acid] is widely used as a growth regulator in floricultural crop production, with foliar sprays as the typical application method. Ethephon efficacy is determined by rate of uptake and subsequent ethylene evolution, which can be influenced by a number of factors, including solution pH. This study examines whether an ethephon substrate drench (100 mg⋅L−1 at a volume of 296 mL per 2.8-L container) would allow for plant uptake in two herbaceous perennials, Verbena bonariensis (L.) ‘Lollipop’ and Veronica spicata (L.) ‘Goodness Grows’, as measured by subsequent effects on shoot growth and days to flower. We also investigated substrate pH effects on ethephon drench efficacy by analyzing the shoot responses to ethephon applied at a range of starting substrate pH (4.5 to 7.0) compared with untreated plants grown under the same substrate pH conditions (controls). One or more measurements of shoot growth (height, width, shoot dry weight) were reduced in both taxa treated with ethephon as compared with controls. Veronica plant growth was not influenced by substrate pH in either the control or ethephon-drenched plants. For Verbena plants receiving the ethephon drench, as substrate pH increased, height and width increased. For example, when ethephon was applied at substrate pH 4.5, finished plant height averaged 32.0 cm, compared with 43.5 cm for those plants that received the drench at a substrate pH of 7.0. Increasing substrate pH conditions also influenced the days to flower in Verbena plants. Ethephon-treated plants at a substrate pH of 4.5 required an average of 6.5 days longer to flower than those at a substrate pH of 7.0. In summary, ethephon drench applications can result in significant growth regulation effects, as seen in both Veronica and Verbena. Furthermore, increasing substrate pH can reduce the efficacy of ethephon drench applications.
Despite the popularity of fountain grass (Pennisetum alopecuroides) as a landscape perennial, little research has been conducted on nursery management practices that maximize its overwintering survival and subsequent spring vigor in container production systems. An experiment was conducted to determine the effect of protective covers (a double layer of insulation fabric, a double layer of insulation fabric plus a single sheet of white polyethylene plastic, or no cover), fertilizer application rate (high and low), and substrate moisture content (irrigated when substrate volumetric water content (VWC) fell below 15% and 25%) on the survival rate and vigor of container-grown fountain grass: straight species fountain grass (SFG), ‘Hameln’ fountain grass (HFG), and ‘Little Bunny’ fountain grass (LBFG). Plants were overwintered in a coldframe and were evaluated for survival rate (percent that survived the winter) and vigor (visual rating scale 1 to 5) the following spring. Survival rate and vigor ratings varied among species. However, the highest survival rates (generally 75% or greater) and vigor ratings (generally 3 or greater) were in treatments that used protective covers, though there was not a clear advantage to using white polyethylene in addition to the double layer of insulation fabric. In treatments that used either of the protective covering methods and the high fertilizer application rate, 25% or less of LBFG survived and had vigor ratings of 1.3 or less. In contrast, 75% of LBFG survived when the low fertilizer rate was used in conjunction with either protective covering method. Substrate moisture content only affected the survival rates of SFG and HFG when no protective cover was used, although these survival rates were less than those with covers. These results suggest that protective covers may serve as a tool to minimize winter damage and improve crop quality for the species used in this trial. Because of the varied capacity among these cultivars to tolerate different fertilizer rates and substrate moisture contents, it is recommended that growers use the results of this study as a baseline for conducting site evaluations to determine overwintering techniques that maximize survival and vigor on their facilities.