VIU Milner Gardens and Woodland

Rhododendron Revival Research November 2022

November 26, 2022 Update

Hello, Rhododendron Society members from Nanaimo (NRS), Cowichan Valley, and Mount Arrowsmith (MARS) and members of Milner Gardens & Woodland!

Kurstin Rispin, student research assistant, here from Vancouver Island University’s (VIU) Rhododendron Revival Research (RRR) project to update the community on the research progress to date. Many things have happened since our last update, and I am excited to share them with you here. First, I will begin with a brief recap of what has been done thus far. After our wonderful tour of the Greig Rhododendron Species Garden at Milner Gardens with John Deniseger and Chris Southwick in late October, we collected and stuck 96 cuttings from 3 hybrid rhododendrons; R. ‘Beauty of Littleworth’, R. ‘Dr.Stocker’, and R. ‘Blue Peter’.  Afterward, the research cuttings were placed in a mist tent at the VIU G.R. Paine Horticulture Center.  The environmental conditions for the mist tent were set using the American Rhododendron Society (ARS) guidelines for propagation. The bottom heat in the mist tent temperature is kept set to 21C and the misting system is set to mist at regular intervals during daylight hours to prevent desiccation.  During the first two weeks in the mist tent, one challenge that arose was the uneven distribution of water across the newly propagated cuttings. Eugene Touchette, Landscape Horticulture Professor, and students worked together to design and rebuild a new misting system in the irrigation course! Now, the sprayers disperse water evenly across the tent, and we can all rest assured that the cuttings are getting the water needed during this propagation stage. We want to give a special thanks to the NRS and MARS for their contribution towards the installation of the new misting system. And now the monitoring begins!

RRR - Research Rhododendrons in Mist Tent

Research Rhododendrons in Mist Tent.   

RRR - Students repairing mist system

Students Repairing Mist System.

Monitoring and care of the research cuttings are carried out using the (ARS) propagation and care guidelines. Each week, I use the record-keeping sheet that I created to collect data on the research cuttings. Additionally, I collect environmental data such as temperature and humidity and track cultural requirements, such as watering or pest and disease pressures. The data I collect on the mist tent environment and the cultural activities will be useful when making decisions for this year’s cutting growth and in future years. In addition to the weekly record-keeping, I stop in and check on the cuttings between classes during the week to see if the mist system is operating correctly or if there are any changes in crop growth. Another tool I use for monitoring the health and growth of the research cuttings is using a sample collection of Rhododendron cuttings outside of the research scope for reference.  I use the reference Rhododendron cuttings to look at signs of early callousing, overwatering, and other root zone issues. In using this sample collection of cuttings, I can infer what may be happening with the RRR cuttings without disturbing them and suggest cultural and environmental changes to encourage rooting success.  Additionally, I am monitoring for any signs of diseased and dropped leaves on the RRR cuttings and will remove any debris to maintain a clean growing environment.

RRR - Research Rhododendrons in Mist Tent

Research Rhododendrons in Mist Tent.

It’s nearly been five weeks since the beginning of the RRR. As expected, the foliage on the research cuttings remains largely unchanged since sticking the cuttings two weeks ago. However, I have observed some early signs of leaf curl, yellowing, and mosaic patterns on some of the foliage.  An exciting observation in the reference Rhododendrons is early signs of callousing, which is a wound response that indicates new root growth is forming. Moving forward, I will continue to monitor changes in the research cuttings over time and record my observations.  This will help build on our understanding of which Rhododendron varieties root successfully using the stem-cutting propagation method.

Thank you for following along with our research and I look forward to updating you at the NRS meeting in the new year!

Kurstin Rispin

VIU Horticulture student grown poinsettias

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