Fall is the perfect time to plant rhododendrons!
The warm soil, increased moisture from dew and rain, and gentle temperatures help these lovely shrubs establish strong roots before winter. Spring planting can be more difficult — sudden heatwaves and early droughts might make it harder for new rhododendrons to survive, let alone thrive.
Climate change is transforming gardening across Canada. The Canadian Plant Hardiness Zones now indicate warmer conditions, with some regions shifting by as much as two zones. For example, Victoria has moved from Zone 7a to Zone 9a, now the warmest zone in Canada. This change presents exciting new planting opportunities but also brings challenges like longer heatwaves, droughts, and unpredictable cold snaps.
Rhododendrons are quite resilient and can curl their leaves to guard against cold, but they remain susceptible to our more frequent rapid freeze-thaw cycles, especially when grown in pots where frozen soil blocks water access for roots. Planting them directly in the ground helps them better withstand such stresses. These plants and others have adapted to cope with gradual seasonal shifts, but the changing climate also requires new approaches.
Proper planting of rhododendrons is vital for adapting to climate change. Rhododendrons favour loose, airy, well-drained, organic, acidic soil with a pH of 4.5 to 6 and thrive in partial shade or filtered light, making them excellent companions for deciduous trees like Quercus, the native Garry oak. Douglas Justice from the University of British Columbia Botanical Garden notes that oaks are highly adaptable to climate change, making them an excellent choice for gardens on Vancouver Island and ideal for shading rhododendrons.
Native clay soils are naturally acidic but often dense and poorly drained, holding excessive water during wetter seasons and drying into a concrete-like medium in drier months. These conditions can suffocate rhododendron roots. To improve clay soil, it is best to loosen it thoroughly, create planting mounds with bark mulch, wood chips, pruning debris, and leaves, and fill planting holes with fine bark mulch and compost for immediate nutrients and better soil structure. The planting medium gradually breaks down to create ideal conditions for rhododendrons. Just avoid using sand or compost containing weed seeds.
Although fall is the prime season for planting, spring plant sales are an excellent opportunity to discover unique rhododendron varieties. Our local rhododendron society provides a great chance to meet generous growers, answer questions by knowledgeable members, and find rhododendrons propagated from cuttings unavailable in stores.
The Cowichan Valley Rhododendron Society will host an engaging Propagating Workshop at “The Hub” in Cobble Hill on Wednesday, Oct. 1, from 7 to 9 p.m.
No experience is needed — just bring your curiosity! The public is welcome to attend any of our CVRS General Meetings at the Hub on the first Wednesday of the month.
Dorothy Kennedy is the president of the Cowichan Valley Rhododendron Society.
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