New plant hardiness zones have been updated in Canada, leading to potential growth opportunities for Prince Edward Island gardeners that were previously limited. The latest Plant Hardiness Zones map, recently revised after over a decade, serves as a guide for Canadians on suitable plant growth based on weather conditions such as temperature and precipitation.
According to John Pedlar, a research scientist at the Great Lakes Forestry Centre in Sault Ste. Marie, Ont., the plant hardiness levels in P.E.I. have generally increased. The map ranges from zone 0 to 9, with each zone further divided into ‘A’ and ‘B’ subzones. Zone 0 represents the coldest regions where only the hardiest plants can thrive, while zone 9 encompasses the warmest areas supporting a wider variety of plants.
In the updated data, the Summerside region has advanced half a zone, moving from 5A to 5B. Meanwhile, Charlottetown has remained at 5B without any alteration. Notably, some parts of southeastern P.E.I. have transitioned a full zone to 6A. The changes are largely driven by factors like extended growing seasons and rising winter temperatures.
The shift in plant hardiness zones is attributed to climate change, which has resulted in a warming trend across Canada. The alterations reflect the intricate dynamics of climate and weather influenced by factors such as ocean proximity, topography, and elevation.
Pedlar emphasized that while considering the potential introduction of new plant species in the region is exciting, the broader concern lies in the negative impacts projected on both natural ecosystems and human activities due to climate change. The research indicates that approximately 80% of Canada has experienced zone increases due to warmer temperatures, with significant changes observed in western Canada, reaching up to two full zones.
The hardiness zones are determined based on long-term averages of various variables, including the coldest month’s lowest average daily temperature, frost-free periods’ duration, rainfall levels from June to November, and other climatic factors. As gardeners explore new plant options, they should also be vigilant about the potential arrival of new pests accompanying the changing hardiness zones, such as the spotted lanternfly, which can pose threats to grapevines and fruit trees.