Before you plan your spring garden, it’s helpful to know your plant hardiness zone. Hardiness zones are defined by the average climatic conditions of the region; knowing your zone will help you determine whether or not a particular plant will grow in your area. The map is divided into nine major zones, the harshest weather zone is 0 and the mildest is 8 (for Canada).
Plant Hardiness Zones – Canada
Calgary and surrounding area falls into hardiness zone 3 with micro-climates of zone 4 in sheltered areas. How closely you stick to the zone guide might be relative to how much you love the plant, you never know, a plant rated to zone 4 or 5 may thrive! Other variables like micro-topography, amount of shelter and local variations in snow cover will all have some effect.
Seed packets and catalogs usually indicate the zones for that type of tree, shrub or flower.
Farmer’s Almanac – Frost Dates
Using the zone map with the frost chart from Farmer’s Almanac to estimate the earliest and latest threats of frost, you should be set to determine whether the plants you want will do well in your garden.
According to the Frost Chart, Calgary’s growing season is about 114 days in length with May 23rd being the estimated last date for frost in spring. September 15th is usually when we could expect frost in fall.
Zone chart references: wikipedia.org and Environment Canada