The West and East coasts may have the best climates for rhododendrons, but they can also thrive in southern areas in the rest of Canada. Many cultivars grow well across Central Ontario and southern Quebec, and all around the Great Lakes. Some evergreen azaleas, which enjoy heat and humidity, are ideally suited to the Golden Horseshoe of Lake Ontario and southwestern Ontario. On the Prairies, owing to dry air, cold and wind, rhododendrons are challenging but not impossible to grow if plants are selected, sited and planted properly, and winter snow cover is reliable.
Here are some tips for those parts of the country with dry, cold winters and/or hot humid summers:
• Most rhododendrons that die do so because of incorrect siting and planting. Learn about your conditions: microclimate, soil quality, precipitation amount, seasonal distribution and temperatures.
• Purchase healthy plants from a reputable grower.
• Rhodos prefer cool, damp conditions. Plant near sheltering oaks and pines to help keep them cool in areas with hot summers; this also reduces temperature fluctuations in winter and conserves moisture.
• Rhododendrons enjoy partial to full sun for good bud set, but avoid sites exposed to full day sun and wind, especially in winter. Water adequately to prevent heat and drought stress.
• It is essential to slash the root ball before planting to encourage growth of new roots. Plant so the top of the root ball sits 2.5 to five centimetres above the surrounding soil and mound mulch on top.
• Make sure plants enter winter well hydrated from autumn rains or watering. A loose mound of leaves or a discarded Christmas tree can help to protect plants.