Propagation Reminders: Poinsettia and Fall Garden Mums
Though its early-May, it’s not too early to start thinking about poinsettia and/or fall mum propagation. I know some growers have already received unrooted cuttings of fall garden mums; however, if you have not received your cuttings yet, but plan to do so, these cultural and environmental propagation reminders will help you prepare to get your cuttings off to a good start.
Prior to unrooted cutting arrival, ensure the propagation environment is clean and sanitized. Start by turning off the mist if it is still running. This will also any algae or other material to dry for easier removal. Growers should remove any leftover spring plant material, debris, or weeds from the propagation space and clean the propagation benches, floors, and mist nozzles. The propagation environment should be free of algae, pests, and weeds. Ensure that you have an action plan to prevent and control disease and pest entry during propagation. Determine your propagation substrate, liner tray, rooting hormone, and surfactant supply is adequate, therefore reducing the likelihood of shortage. Before filling any propagation trays, determine initial substrate pH and electrical conductivity (EC) for low or high pH or EC problems. During propagation, monitor propagation substrate pH and EC by performing 1:2 Extraction, SME, or PourThru procedures. For mums, optimal substrate pH is 5.8 to 6.2 and substrate EC should remain below 1.5, 3.3, and 3.3 mS/cm, based on the 1:2 Extraction, SME, or PourThru methods, respectively. For poinsettias, optimal substrate pH is 5.5 to 6.5 and substrate EC should remain below 1.5, 3.3, and 3.3 mS/cm, based on the 1:2 Extraction, SME, or PourThru methods, respectively.
Prior to cutting arrival, ensure that your mist system(s), humidifiers, shade or energy curtains, and/or fertilizer and acid injectors are properly working and calibrated. Once cuttings have arrived, stuck, and placed in the propagation environment, begin misting to rehydrate cuttings. It is important to remember mist is not and should not be used as a form of irrigation. Adjust and reduce misting intervals upon callusing, root initiation, and root formation. Too much mist can delay rooting, cause stretch, and rot. Mist should be discontinued upon root formation and irrigation can begin. Maintain a daily light integral (DLI) of 10 to 12 mol·m-2·d-1. To do so, one may have to deploy shade or apply white wash to the greenhouse glazing material during summer months. High DLIs during propagation will produce higher quality rooted cuttings, but too high of light can become detrimental. Provide long days or night interruption photoperiodic lighting. Shading the propagation environment will assist in temperature management and control. Maintain an air and propagation substrate temperatures of 70 to 72 ºF.
W. Garrett OwenAssistant Professor of Sustainable Greenhouse and Nursery Systems, The Ohio State University
W. Garrett Owen is an Assistant Professor of Sustainable Greenhouse and Nursery Systems in the Department of Horticulture and Crop Science at The Ohio State University. He has an appointment in research, teaching and Extension. His area of expertise is plant nutrition; plant growth regulation; and production problem diagnostics.