Over a month ago, anticipating the nebulous arrival of spring, I started a plant hardiness zone colouring map. This was to add to the complement of colouring maps and mapping worksheets I'd been making.
Alas, despite the best intentions of having it finished within a week, quarantine homeschooling has been absorbing every morsel of my time. I'm sure many of you can relate.
As cartographer Daniel Huffman observed following a cartography live-stream event where women were under-represented, a probable cause was that women were otherwise occupied taking care of children, doing household tasks and homeschooling their kids as all the schools are closed. I can fully corroborate this, as it's been virtually impossible to do any mapping with so full a slate of other responsibilities.
There are many aspects of homeschooling I'm enjoying, like making my kids all kinds of worksheets about subjects that capture their imaginations and interest. (at least I'm using my graphics skills, tra la)
As we grow a large vegetable garden every year, understanding plant hardiness zones is important. This was something I was interested in teaching my small green thumbs and one I'm happy to share.
What are plant hardiness zones?
Plant hardiness zones are geographic areas primarily defined by their extreme minimum temperatures. They vary with altitude and latitude all across the world. These zones are referenced by gardeners (or anyone interested in growing plants) to determine whether a particular plant can thrive, or survive in their area.
Every plant has its own particular temperature tolerance, so it's important to know which ones will over-winter in the hardiness zone you happen to live in.
Generally, local nurseries and seed providers stock plants and seeds that are compatible with surrounding hardiness zones, though this is not always the case.
The USDA hardiness system divides temperatures up into 12 zones (note that there are 2 zones per number, a and b.
Canada follows an adapted version of this system and includes other important variables such as rainfall amounts, mean maximum snow depth and mean frost free period. Canada's zones range from 0a to 9a.
Difficulties with hardiness zone maps
Data and temperatures for hardiness zones is an average of a few decades. Unfortunately in Canada at least, these are old numbers. The averages have not been updated since 2010 - a decade ago. Climate change is going to alter the extreme minimum averages, snowfalls and frost free periods across all geographies. It likely already has. It would be beneficial if these zones were updated to include recorded changes over the past decade.
The boundaries between zones are not absolute and variations within zones occurs, so depending on the exact location of a person's vegetable patch or garden, their zone might share characteristics of one or two zones.
Creating the hardiness zone colouring map
There is no vector data available for hardiness zones from Natural Resources Canada, so it was necessary to make my own. A version of the above map was used to digitize (digital tracing by hand of features from images to create vector data) the hardiness zone boundaries. This was tricky in places and required necessary generalization (simplification) of some areas, especially in and around the Rocky Mountains as the broad range of elevations creates many zones packed into a small area.
The result is a patchwork of wavy lines showing interesting geographic variations in temperature that are often surprising in places.
While colouring, see if you can notice those places and imagine what might be causing those anomalies.
This colouring map is a fun one. It uses a broad range of bright, vibrant colours to identify each hardiness zone which makes for an eye-popping, vivid result.
This map doesn't show place names or other large geographic features. At this scale it would make the map too cluttered and difficult to read. Locate the general area of where you live, draw a black circle there and label it.
The hardiness zones were too detailed to be properly visible on a single printer page, so it's enlarged to fit on two sheets. The file consists of two maps: one reference map with the plant hardiness zones labelled and the other the blank colouring map for you to fill in. Pencils ready? Excellent.