The map provides an indication of the locations suitable for growing of trees and
shrubs based on their ability to survive. Gardeners are familiar with this type of information because they
use it to determine which plants to grow.
Methodology
This map shows an index of suitability for growth of trees, shrubs
and flowers. It is calculated for all the areas in the country,
using an equation that integrates climatic data from the 1930 to
1990 period. The climatic data used to calculate the index are the
minimum winter temperatures, the length of the frost-free period,
summer rainfall, summer maximum temperatures, snow cover, January
rainfall and the maximum wind speed. Elevation data were also taken
into account because of its direct effect on temperature and precipitation.
Data are derived from a 2 kilometre by 2 kilometre grid.
Interpretation of the Map
The map is divided into nine major zones: the harshest is 0 and
the mildest is 8. Each major zone is divided into subzones a and
b (for example 3a and 3b) where zone a is slightly harsher than
zone b. These nine zones are associated with probabilities of plant
survival in relation to the average climatic conditions. However,
some variations can occur within a zone because of significant local
factors such as a change in the topography, variations of snow cover,
year-to-year weather variations, exceptional weather events and
even gardening techniques which have a significant impact on plant
survival in any particular location.
The information presented on this map only gives a general indication
of plant hardiness and is accurate to plus or minus two zones. In
fact, errors can occur in station data and estimates between stations.
The weather also fluctuates from year to year and the local variations
may not be reflected on the map.
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