Benzyladenine Increases Branching of Herbaceous Perennials

Many of the herbaceous perennials, especially the newer cultivars of Echinacea, are poorly branching, slow to fill out the pot, and produce few propagules. Configure (6-BA, Fine Americas, Inc.), a new product recently labeled for branching of floricultural crops, was evaluated on a variety of perennials over two seasons. Configure was applied once as a foliar spray at rates of 0, 300, 600, 900 or 1200 mg/L to established plants grown in 1.1-L pots filled with a peat/pine bark medium. Plant height and number of branches were determined at 2-week intervals after treatment (WAT). In spring trials, Configure improved the basal branching of Echinacea purpurea ‘Double Decker’ with a three-fold increase in the number of new shoots per plant with a single foliar application of 300 mg/L (control 1.0 vs. 300 mg/L 3.8 shoots at 2 WAT). Higher rates further increased the number of basal shoots. Echinacea purpurea ‘White Swan’ had a better branching habit and was more responsive to Configure with increased branching at 4 WAT with treatment of 300 mg/L; again higher rates increased the number of new branches. Vinca minor ‘Sterling Silver’ showed a significant quadratic increase in the number of branches at 4 WAT with Configure which did not persist but suggests that there may be value in multiple applications. Coreopsis verticillata ‘Zagreb’ plants treated with Configure had increased branches at 2 WAT that also did not persist. In Fall trials, branching of Echinacea ‘Ruby Star’ increased nearly 2-fold (control 2.6 vs. 300 mg/L 5.0 shoots) at 2 WAT. Similar results were observed with Echinacea ‘Magnus’. Clematis jackmanii, Phlox paniculata ‘Bright Eyes’, Buddleia × weyeriana ‘Honeycomb’ and Coreopsis rosea ‘Sweet Dreams’, were not responsive to Configure. In all tests, positive results persisted throughout the six to ten week studies. Configure offers a new tool for improving the finished quality and propagation potential of Echinacea cultivars and the potential for improving branching of other herbaceous perennials. INTRODUCTION Many producers are using a bedding plant production model to fast-track their herbaceous perennials. Many of the newer cultivars of Echinacea branch poorly (Whitman et al., 2007) and are therefore slow to fill out the pot under spring production systems. In addition, these crops produce few propagules. Plant growth regulators, including benzylamino purine (benzyladenine, 6-BA) or combination products that include 6-BA, increased branching of Hypericum calycinum (Thomas et al., 1992) and Verbena × hybrids (Svenson, 1991), but had no effect on lateral branching of florist azaleas (Rhododendron spp.; Bell et al., 1997) or boxwood (Buxus sempervirens; Musslewhite et al., 2004). Benzyladenine increased lateral offshoots of 16 of 18 perennial species treated with 1000 mg/L 6-BA applied as a spray and crown drench (Martin and Singletary, 1999). The use of 6-BA on Hosta cultivars (Keever, 1994) and Christmas cactus (Schlumbergera truncate; Heins et al., 1991) has a long history of efficacy and improved branching and/or flowering. However, a commercially labeled and regularly available 6-BA product was not available to the horticulture trade until 2007. Fine Proc. X IS on Flower Bulbs and Herbaceous Perennials Eds.: J.E. van den Ende et al. Acta Hort. 886, ISHS 2011 164 Americas, Inc. (Walnut Creek, CA, USA) labeled an effective 6-BA product, Configure, in most states in United States. The label details its use on Hosta, Echinacea and Christmas cactus. This report details our studies conducted to date on Echinacea and other herbaceous perennials. MATERIALS AND METHODS The same treatment application procedure and experimental design were followed for each trial. After establishment and resumption of growth, about two weeks after potting unless otherwise stated, the plants were treated with a foliar spray of Configure at rates of 0, 300, 600, 900 or 1200 mg/L using a hand-held CO2 pressurized sprayer (R&D Sprayers, Inc. Model AS, Opelousas, LA, USA). Sprays were evenly applied over a given time period to apply 210 ml/m to a square meter area in which five plants of each species were placed. Each plant species was set up as an individual experiment with plants arranged in a completely randomized design with five single plant replications. Data were collected at two-week intervals from four to ten weeks after treatment (WAT) depending on the crop and trial and included plant height (from rim of pot to top of plant, in cm), number of branches and observations of phytotoxicity. Plant height and branching data were subjected to linear and quadratic regression analysis. Spring Trials Plugs of Coreopsis verticillata ‘Zagreb’, Vinca minor ‘Sterling Silver’ and two cultivars of Echinacea purpurea, ‘Doubledecker’ and ‘White Swan’, were planted into 1.1-L plastic pots filled with a peat-pine bark mix (Fafard 3B, Conrad Fafard, Inc., Agawam, MA, USA) and irrigated as needed with 200 mg N/L (Peters 20-10-20, The Scotts Co., Marysville, OH, USA). Data were collected for six to ten weeks depending on the crop. Fall Trials Two fall trials were conducted, one at a commercial nursery (Riverbend Nursery, Riner VA, USA) using Echinacea purpurea ‘Magnus’ and Clematis jackmanii. The Echinacea plants were grown in quarts (1.1-L) pots and the Clematis in trade gallon pots (3.4-L) filled with a peat/bark medium (Metro Mix 360, Sun Gro Horticulture, Bellevue, WA, USA) amended with perlite in early summer (June/July). Configure treatments were applied in early September as described above. Data collection was limited to once at 4 WAT. The second fall trial was conducted the following year in the on-campus greenhouse using Echinacea purpurea ‘Ruby Star’, Phlox paniculata ‘Bright Eyes’, Buddleia × weyeriana ‘Honeycomb’ and Coreopsis rosea ‘Sweet Dreams’ plugs planted in 1.1-L plastic pots filled with a peat-lite media (Fafard 52, Conrad Fafard, Inc.). Plants were fertilized as above and allowed to establish and resume active growth after transplanting (about two weeks after potting) before Configure was applied as described above. Plants were measured at 2 and 4 WAT. RESULTS AND DISCUSSION Spring Trials Echinacea ‘Double Decker’, which is poorly branched in spring production, exhibited increased branching at 2 weeks after application of Configure. With a single application of 300 mg/L Configure, we more than doubled the number of basal breaks of ‘Double Decker’, from 1.6 branches per control plant to 4.2 branches on the treated plants at 8 WAT. A single treatment of 1200 mg/L further increased the branch number to 6.8 per treated plant (Fig. 1). Furthermore, the branches were “normal” in appearance and continued to grow and develop normally. There was a delay in flowering, four to seven days, especially with the higher rates. There was no phytotoxicity identified on any of the treated plants. There were no significant effects on plant height with Configure.