Plant hardiness site help


To some there seems confusion and controversy about Canada's new Plant Hardiness zones map. Zones have stayed the same in many areas, changed slightly in a few areas, but seemingly more in a couple of key noticeable locations - parts of southern Vancouver Island and a few spots in deep southern Ontario. Why is this, what does it mean for growers and where do we go from here?

To understand the changes and implications it is important to dig into how the new and original maps were created (see Ouellet and Sherk 1967; McKenney et al. 2001).
1) The map is the result of a mathematical formula that adds together several long-term climate factors (i.e. mean minimum temperature of the coldest month, frost free period in days, rainfall June through November, mean maximum temperature of the warmest month, rainfall in January, mean maximum snow depth and maximum wind gust in 30 years).
2) The formula was established in the early to mid 1960s and came about by statistical analysis of the survival of 174 ornamental trees and shrubs at just 108 locations across the country.
3) The formula gives a hardiness index (usually a number between 0 and about 100). A 42.2 would be in zone 4a, 68.3 would be in zone 6b and so on.
4) In the original work the index was calculated at just 640 weather stations across the whole country and the map produced by hand drawing the general zones between these stations.

The new zone map was produced by creating new climate maps of all the variables needed for the formula. These maps are actually computer models that were "gridded" - values for each climate variable were estimated across the country at a spacing of approximately every 2 km. We actually did this for two time periods - 1930-1960 and 1961-1990. The first time period roughly matched the period of the original work and matched the original map surprisingly well even though they were developed with different methods! This is an important point because everyone's point of comparison is the original map. However, we also included the effects of elevation on our climate maps. This significantly improves the quality of the maps because elevation has such an h2 influence on climate. Elevation influences are very noticeable in mountainous areas, more subtle in other areas but still present.

Our aim is to go beyond a single general map and develop potential range maps for individual species of trees, shrubs and perennial flowers. Our approach is to develop a climatic profile for each plant using new continent-wide climate models. These climatic profiles will be mapped giving an indication of the possible range of each species.

So we need participation from experts and the public all over Canada, and ideally the northern United States as well. Contributors need to identify what plants, from a comprehensive list, survive at their location. Once enough data are entered to develop a climatic profile the range maps will be generated. These range maps will be continually updated as more data are submitted.

More information is contained in "Getting Into the Zone - what does Canada's new plant hardiness zones map really mean?" (In press)


Data use

We respect your right to privacy and will therefore not share your personal information with others.

Plant data gathered on this site will be used for research and mapping. Users are asked for e-mail addresses in the event that researchers need to verify the accuracy of information that has been reported. Only maps and plant location information are provided in the interactive mapper.


Species selection

Select a genus then select the species from that list. The list may be refined to plant categories by selecting one of the six options and then selecting the update button. Alternatively you can do a search, by genus or common name, from the main page.
E-mail us if the plant you wish to report is not listed on the site, or to report any nomenclature errors.


Searching for a particular species

From the main page enter a search string and select the Search button.
Species name, and common name fields are searched in the species database. Secondly the genus database is searched to find matches there. This will return a list of species and genera that have a match in their name.
Simply clicking on a species entry will take you to its entry page. Selecting a genus entry will give you a list of the species for that genera in the same fashion as species selection above.


Plant description links

This provides a link to another site with further information about a plant. Correct plant identification is important for this project. If you are uncertain about your specific plant please follow the link and check it out.


Tips on Entering Data

Please only list plants that you are certain about their identity.

Users can enter data for multiple locations by changing the Latitude and Longitude for each entry. By doing this you could report data in both your home garden and cottage garden, for instance. There is no need to register more than once to allow for multiple location entries. However, please be sure to change the Province box setting for each entry, if this applies to your situation.

The data gathered on this site will be used for scientific research. Users are asked for e-mail addresses in the event that researchers may need to verify the accuracy of information that has been reported.


Plant location information

It is critical that this information is as accurate as possible (within 1-3km). If you already know your longitude and latitude enter it in decimal degrees (eg. -89.513, 53.1586) Location information should have at least three decimal places. For privacy purposes the plant location information reported on the maps will only be to two decimal places.

Longitude measures the degrees east of Greenwich England. (in North America we are west of Greenwich so longitude is negative)
Latitude measures the degrees north of equator.

There are many ways to find your location but here are some options if you do not already know it. Accuracy is important but we understand that many of the following options are only accurate to two decimal places.

1. If you have access to a GPS unit (global positioning system) use it.
2. You could locate your longitude/latitude on a topographic map.
3. Many web sites that allow you to enter your street address and get a location. Please record the Decimal Degrees version for use on the Plant Hardiness site.


Site information

Make your selections for the following as best you can.

Longevity - refers to how long the species has survived at this location. It should have survived for at least 3 years to be included.

  • 3-5 years
  • 6-9 years
  • > 10 years

Exposure - to the sun

  • Full sun
  • Part sun
  • Shade dappled
  • Shade

Protection - use your best judgment to make this selection

  • Extra winter protection given (e.g. wrappings, deep mulching, etc.)
  • Next to house (within 2 metres/6 feet of a building)
  • 2 to 10 metres from house (6 - 30 feet)
  • > 10 metres from house (more than 30 feet)

Performance - describes how well the plant performs at your location

  • Little or no dieback over each winter
  • Minimal dieback less than 25% of the plant dies back over each winter.
  • Severe dieback > 25% or more of the plant dies back over each winter.

Soil - Choose the one that is most dominant in your site. Use your best judgment or select unknown.

  • Sand
  • Loam
  • Clay
  • Unknown

Comments box

This is handy for recording a cultivar name, if known. Any special notes about plant performance could also be listed here. Please refrain from leaving personal comments about plants, such as "I really like this!"


Large data sets

For BOTANICAL GARDENS and other users with large amounts of data: if your plant records can be put into a spreadsheet format, it may be possible to import them more quickly into this site. Please e-mail us about this.



Cultivar - short for "cultivated variety". This refers to varieties of plants that are maintained only through the efforts of mankind. Many of our common garden plants are cultivars -- discovered or bred for particular characteristics such as improved colour, disease resistance, large or dwarf habit, variegated leaves, etc.

Genera - plural for the word genus. One genus, two or more genera.

Genus - A scientific classification that taxonomists use to group together plants with common characteristics. A genus may contain numerous species. e.g. All species of roses are members of the genus Rosa. All species of maples belong to the genus Acer.

Herbarium - in scientific terms this refers to a collection of dried plants pressed and mounted on paper sheets then stored systematically for future study. For purposes of this site it refers to Internet links which provide further information and usually images for each particular plant species.

Species - A taxonomic classification for a group of plants within a genus that differ from other similar plants in only minor ways. e.g. Within the genus Rhododendron there are many distinct species. Plants within these species are similar to each other, but differ in some distinct way from other Rhododendron species.

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