The objective of this study is to evaluate the branching effect of benzyladenine (BA) on herbaceous perennial plants during the production of rooted cuttings (liners) and to examine and quantify the root growth of these liners using multiple methods of root evaluation. Five crops were studied: Agastache Clayt. Ex Gronov. ‘Purple Haze’, Gaura lindheimeri Engelm. & A. Gray ‘Siskiyou Pink’, Lavandula ×intermedia Emeric ex Loisel. ‘Provence’, Leucanthemum ×superbum (Bergmans ex J.W. Ingram) Bergmans ex Kent. ‘Snowcap’, and Salvia ×sylvestris L. (pro sp.) ‘May Night’. After rooting but before transplant, BA was applied to rooted cuttings as four treatments: controls (0 mg·L−1), one application of 300 mg·L−1, two applications of 300 mg·L−1, or one application of 600 mg·L−1. Results varied by crop; all crops except Salvia had increased branching as measured as either increased lateral or basal branches and/or increased leaders at 3 to 4 weeks after initial treatment. Four crops showed reduced root growth, whereas Gaura was unaffected. Root dry weight was found to be highly correlated with root surface area and root volume. After transplant and growing out, branching of the finished plants was increased in Gaura and Lavandula, unaffected in Salvia and Leucanthemum, and decreased in Agastache. Treating rooted cuttings with BA before transplant increased branching but the effects were not long lasting, which suggests that additional applications at or after transplant may improve finished plant quality. Reductions in root growth noted in rooted cuttings did not affect the growth of finished plants. Chemical names: N-(phenylmethyl)-1H-purine-6-amine (benzyladenine, BA).
Mara Grossman, John Freeborn, Holly Scoggins, and Joyce Latimer
Mara Grossman, John Freeborn, Holly Scoggins, and Joyce Latimer
Foliar spray applications of plant growth regulators (PGRs) benzyladenine (BA) and dikegulac sodium (DS) on herbaceous perennial liners and transplants were evaluated to determine effects on branching and quality. PGRs were applied three times (main plot): liner (24 h after removal from mist), post-transplant (5 to 7 days after transplant), or both (applications at liner and post-transplant). PGRs (subplots) were applied at concentrations of 400, 800, or 1600 mg·L−1 DS; 600 mg·L−1 BA; or a combination of 400 mg·L−1 DS and 600 mg·L−1 BA (DS/BA). All studies included an untreated control. Sedum spectabile ‘Autumn Joy’ treated with PGRs at both application times had a 100% increase in branching compared with either single application time. Applied post-transplant, 800 mg·L−1 DS, BA, or DS/BA increased branching. Applied at both times, all DS concentrations or BA tripled the number of lateral branches per plant, whereas DS/BA resulted in a 4-fold increase in number of branches. Sedum treated with 1600 mg·L−1 DS at liner, post-transplant, or both application times was shorter than controls; plants sprayed with 1600 mg·L−1 DS at both application times were stunted. Phytotoxicity (yellow, narrow leaves) was present in finished plants treated with 800 or 1600 mg·L−1 DS or DS/BA post-transplant or with 1600 mg·L−1 DS applied both times. Gaillardia aristata ‘Gallo Red’ treated with PGRs at both application times had increased branching compared with plants subjected to a single application. Number of branches was increased by liner application of 400 mg·L−1 DS, post-transplant applications of DS/BA, or applications both times of BA or DS/BA, whereas applications both times of 1600 mg·L−1 DS decreased branching and caused stunting and chlorotic foliage. In application as liners or at both times, all PGRs except 400 mg·L−1 DS caused 16- to 33-day delays in flowering. Branching of Phlox paniculata ‘Bright Eyes’ was unaffected by application time. Only Phlox treated with BA or 1600 mg·L−1 DS at both application times had increased branches, although plants treated with 1600 mg·L−1 DS were shorter than controls and had phytotoxicity in the form of narrow, yellow leaves. Nepeta racemosa ‘Walker’s Low’ treated with PGRs post-transplant or both application times had more branches than plants treated with PGRs once as liners. Number of branches was increased with BA or 800 mg·L−1 DS applied post-transplant or 1600 mg·L−1 DS, BA, or DS/BA applied both times, but the plants treated with 1600 mg·L−1 DS were stunted and had yellow leaves. Neither BA nor DS affected branching in Delosperma ‘Table Mountain’. Application time did not affect branching in Achillea ‘Moonshine’; only both applications of BA increased the number of branches in Achillea, whereas either single application of 1600 mg·L−1 DS or both applications of 800 or 1600 mg·L−1 DS caused phytotoxicity and stunting. Chemical names used: N-(phenylmethyl)-1H-purine-6-amine [benzyladenine (BA)], sodium 2,3:4,6-bis-O-(1-methylethylidene)-α-L-xylo-2-hexulofuranosonate (DS)
William K. Harris, Joyce G. Latimer, John F. Freeborn, Margaret Aiken, and Holly L. Scoggins
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.
Christina M. Twardowski, Jaime L. Crocker, John R. Freeborn, and Holly L. Scoggins
Some popular garden perennials yield low numbers of viable cuttings per stock plant or produce cuttings that are slow to root, preventing propagators from meeting demand for rooted liners. We quantified the effects of a range of nitrogen (N) rates from 0 to 300 mg·L−1 N applied to stock plants on the number of cuttings (yield), rooting percentage, and subsequent root development of cuttings. Species studied include ‘Siskiyou Pink’ gaura (Gaura lindheimeri), ‘Pixie Star’ dianthus (Dianthus alpinus), perovskia (Perovskia atriplicifolia), and ‘Mainacht’ salvia (Salvia ×sylvestris). We found 100 to 150 mg·L−1 N to be the best rates for producing quality rooted cuttings. Little benefit was obtained from the higher rates, and the 0- and 50-mg·L−1 N treatments produced the lowest number of potential cuttings across all species.