Plant hardiness zones Canada / USA

Discussion in 'Plants: Science and Cultivation' started by Georgia Strait, Oct 1, 2019.

  1. Georgia Strait

    Georgia Strait Active Member

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    i notice that these forums have guests from both sides of the Cascadia border and beyond

    I am curious how the Agric Canada zones compare to USDA zones

    And do universities in the Pac NW like UBC and OSU have projects to keep zones updated not so much for home leisure gardening but more importantly Agri-Food and other industrial agriculture

    I notice Ag Canada link below has a comparison of 1967 map and updated recent map ... aside fr debating climate change etc - I suppose plain paving of paradise human expansion and suburbia has changed some temperatures over recent decades - a simple example would be how much of the western Fraser Valley and delta are heat retaining paved and built areas.

    (And I know the old classic Sunset magazine Western Garden Book has a proprietary zone map that crosses the border we share here - there is a lot of detail tho one has to translate plant labels )

    Here is USDA USDA Plant Hardiness Zone Map

    Here is Ag Canada or however the federal ministry is called today
    Plant Hardiness Zones in Canada - Index

    And here is classic Sunset garden zones map https://www.sunset.com/garden/climate-zones/sunsets-garden-climate-zones/?amp

    I also read the RHS magazine and wonder if UK has a number zone system relatable to Canada / USA

    Just a curiosity as I do like to read plant labels and notice which plants do well (or not) in the various places I visit (does every town have the one house with the palm tree burlap-wrapped for winter?!)
     
  2. wcutler

    wcutler Esteemed Contributor Forums Moderator VCBF Cherry Scout 10 Years

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    [Edited] It is my fault that this discussion on climate zones got going in another thread. I have moved the whole discussion to this existing thread, which had no replies.

    I am leaving my original reply from that thread, which doesn't make a lot of sense here, but there is a reply that references it:

    I don't know the zones and how the Canadian ones map to the US ones, but that seems too warm a zone name for your location. My experience with cherry tree blooming times is that North Vancouver is colder than Vancouver, though your alcove might make for a warmer micro- (very micro-)climate.​
     
    Last edited: Nov 16, 2019
  3. Gwen Miller

    Gwen Miller New Member

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    Here's where I found the zone calculator, using data from 2000.

    Geospatial Platform Viewer

    The mapped results for my area are attached. I'm not far above the water, so it's warmer than higher up the mountainside, Lynn Valley or Upper Lonsdale.

    I'd be curious to know how the Canadian, U.K. and U.S. zones compare too.
     

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  4. Margot

    Margot Well-Known Member

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    When I looked at a Plant Hardiness Zone map a few days ago, I was surprised to see my area classified as zone 9a, not 8b as I had thought. I have my doubts.

    It's hard to tell when the Canadian PHZ map was last updated. A few official websites talk about major changes in 2000 Plant Hardiness Zones of Canada | Open Government, Government of Canada , while another shows a map that was updated in 2017. There is conflicting information . . . while one government site says that the Canadian zones range from 0 to 8, the 2017 map indicates a zone 9 - but the map can't be enlarged enough to see accurately, especially for coastal BC. It's very frustrating! http://planthardiness.gc.ca/images/PHZ_2014_CFS_Map_30M.pdf

    The Canadian Plant Hardiness Zone map was updated in 2000.
    Plant Hardiness Zones of Canada | Open Government, Government of Canada
     
  5. Gwen Miller

    Gwen Miller New Member

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    Hi Margot - I found the site was easier to navigate from my laptop than my phone. The map had a slider bar to zoom in and out, and there were icons above the map that let you change view from streets to satellite to topographical and more. I did see info on coastal areas. The coloured format shown on my screenshot attachment displayed the best; the other views loaded too slowly.
    In some of my experimental clicking, labels popped up with a date of 2010. So it's unclear when the data was collected, vs. presented. I agree the map seemed pretty liberal with the zones 8 & 9. Maybe a call to Agriculture Canada might shed more light on this.
     
  6. Margot

    Margot Well-Known Member

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  7. Sulev

    Sulev Active Member

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    According to the Laidbackgardener's blog (Comparing US and Canadian Hardiness zones – Laidback Gardener) there is a rule of thumb: "To find the Canadian hardiness zone, add 1 to the American zone."

    These hardiness zones are generally about the coldest temperatures in wintertime (annual extreme minimum temperature), not about when the spring warmth arrives. Blooming time of cherries is not a good indicator about how mild the coldest winter month is. Usually areas close to the ocean have milder winter than inland regions, but spring (and actually the whole summer) may be chillier there, because the ocean cools the air down even for several months after winter has gone.
     
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  8. Sulev

    Sulev Active Member

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  9. Gwen Miller

    Gwen Miller New Member

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    Yes, the site is difficult to use. Using your link, I chose the green 'Get the App' button, which loaded a page with the map of Canada, with the search box to enter the desired postal code displayed. Your area has one of the 2010 flags I mentioned.
    (Bet it won't work the same way tomorrow!)
     

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  10. Margot

    Margot Well-Known Member

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    Okay Gwen, we're on the same page! It was your mention of
    that I was especially interested in. I know how to do that on Google maps but don't see how to do it for the plant hardiness map.

    I finally found the plant hardiness map that showed my area (not quite the same as shown on my attachment) to be zone 9a. British Columbia Interactive Plant Hardiness Zone Map It appears to be an American site that apparently doesn't use data from the Canadian government analysis.

    Here is an interesting article which explains the differences between the Canadian and the US Zone maps.
    By: Anne Marie Van Nest, Canadian Gardening's horticultural editor (2007)

    The United States Department of Agriculture hardiness map and the Canadian hardiness map shouldn't be used interchangeably. The two systems differ anywhere from half a zone (warmer or colder) to as much as two zones, preventing an exact exchange or even a standard means for conversion.

    Additionally, the two maps are based on different criteria. For the NRC map, plant survival data and climatic information such as minimum winter temperatures, length of frost-free days and maximum wind speed are used to define its nine (0 through 8) zones, which are subdivided into colder (a) and warmer (b) regions.

    The hardiness zones of the USDA map, on the other hand, are based only on average annual minimum temperatures. The map is divided into 11 zones (1 to 11), eight of which are subdivided into colder (a) and warmer (b) areas.

    The best way to use USDA plant hardiness zones when NRC information is not available is to locate your garden on each map and note the corresponding zone. For example, Edmonton is indicated as 3a on the NRC map and 3b on the USDA map, so any plant listed as USDA Zone 3 or lower should survive. Also, always find out which hardiness system is being used by your local nursery or gardening reference; if it's USDA, ask if the NRC hardiness zone is available.
     
  11. Gwen Miller

    Gwen Miller New Member

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    Yes, the site is difficult to use. Using your link, I chose the green 'Get the App' button, which loaded a page with the map of Canada, with the search box to enter the desired postal code displayed.
    (Bet it won't work the same way tomorrow!)
     
  12. Gwen Miller

    Gwen Miller New Member

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    I keep forgetting to complete my postings - sorry about being delayed. The different views came up just above the map under the BASEMAP icon following LEGEND DATA CONTENTS. Hope it works for you, Margot.
     
  13. vitog

    vitog Well-Known Member 10 Years

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    I don't know if this helps, but here is my take on Canadian/USDA plant hardiness zones. The latest map from the Government of Canada uses 1980-2010 data. The direct link to this map is at Plant Hardiness Zones of Canada . This is a large map that is easy to zoom to a particular location, but it is helpful to adjust the opacity of the zone colour overlay. You can do that by clicking on "Contents" at the upper left of the map, then click on the arrow to the right of the "Plant Hardiness Zones of Canada 2010" layer, and finally click on "Set opacity...". Adjust the slider so that you can see the underlying basemap beneath the zone colours. Margot, this map shows the entire area around Nanoose Bay to be zone 8a.

    Canada also publishes a map of Canada showing Plant Hardiness Zones USDA . This is a smaller map with lower resolution, but you can get a reasonable idea of the equivalent USDA zone for your area. For example the coastal area around Nanoose Bay is zone 9a. And it shows that parts of that area that are Canadian zone 8a can be USDA zones 9a, 8b, or 8a; so, there is no direct correspondence. I checked my own location in North Burnaby, and it is zone 8b on both maps.
     
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  14. Gwen Miller

    Gwen Miller New Member

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    Vitog, thanks for this! Your tips really improved map functionality. I'm embarassed that I avoid reading legends or checking links; there's just so much information. I'll print your post to have it at my fingertips in my gardening notes so I can find it again next time I'm wondering.
    And yay!! I'm always thrilled to see my 20 year old Robinia pseudoacacia 'frisia' shows up!! (From the outer reaches of the galaxy, one of the neighbors might say.)
     

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  15. Margot

    Margot Well-Known Member

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    I know from my years living in Burnaby that the northern part is warmer than the south. I remember my amazement seeing a large rosemary shrub blooming in N. Burnaby - couldn't believe it! Now, living in Nanoose Bay, I find so many plants that succumbed my 8a S. Burnaby garden flourish here . . . Laurus nobilis, Phormium, Grevillea, tender rhodos like 'Snow Lady', - and Rosemary - so much so that I believe my garden is zone 8b, not 8a regardless of what the map says.

    After all is said and done, maps are just a guide. Gardeners are famous for 'pushing the envelope' when it comes to planting borderline hardy treasures in their gardens; hoping the weather will be mild enough and dry enough for long enough to make the purchase worthwhile. Then, when things die, we can look at a hardiness map and say, "Well, of course!"
     
    Last edited: Nov 17, 2019

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