Gardening by Judith Adam A new kind of weather The 2025 summer season presented unexpected challenges to every garden. Urban postage-stamp spaces, small vegetable patches, expansive suburban lawns and natural cottage landscapes – all were affected by intense heat, weeks of drought or flooding rain and changes in the growth patterns of familiar plants. Weather systems we once took for granted are now delivering dramatically different behaviour, and gardeners are challenged to understand how to adapt to these new influences. A guideline map of changing weather conditions in every habitable Canadian location would be a useful aid to understanding the new climate systems – and we’ve got one. Natural Resources Canada acts as a perpetual weather monitor, analyzing detailed statistics regarding regional weather conditions over 30-year periods. The analysis is applied to a map of Canadian plant hardiness zones and indicates the seasonal expectations of low and high temperatures through all four seasons. The last climate zone map was produced in 2014, and the most recent map became available in 2025 (based on data from 1991 to 2020). For the first time, there are significant changes in regional temperature predictions, with more than 80% of Canadian land locations showing an increase in up to two full temperature zones. In simplest terms, this means more moderate temperature in deep winter with less penetrating frost in soil, bracketed by extended autumn and spring periods and considerably warmer summers with frequent droughts. This is important news for growers of every kind, from a window box full of petunias to a field of canola. The plant hardiness zone map is based on only six criteria applied to specific locations: lowest average daily temperature in the region’s coldest month; days of frostfree periods above zero centigrade (0 C.); amount of rainfall from June to November; highest average daily temperature during the zone’s hottest month; severity of winter; and maximum snow depth and wind gust over 30 years. Locations on the map are divided into nine regions, from warmest (zone 9) to coldest (zone 1); and each region is divided into an A section indicating colder and B section indicating warmer. As examples of the statistical changes, the new climate map indicates that Timmins, Ont. has risen by half a zone rating from 2a to 2b, a moderate rise allowing for a selection of new plants that will survive in the warmer winter. But Winnipeg, Man. has risen by a full zone rating from 2b to 3b, and that is a significant increase of warmth that will affect both garden plants and the harvesting dates for agricultural crops. These climate changes are not predictions; they are already upon us. To find the current hardiness zone statistics for your garden, an internet search for ‘Canada’s Plant Hardiness Site’ will take you to all the information for your specific location. Winter weeks are a good time to contemplate the changed growing conditions in Canadian gardens. Warm winters with longer frost-free periods and record-breaking summer heat with erratic rain can turn a garden upside down. It’s time to understand seasonal changes, and what we can do to help gardens adapt. Record-breaking heat is here to stay in Canadian gardens, but it’s not all bad news. Gardening in Changing Weather Conditions 54 | www.snowbirds.org
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