Zones

Discussion in 'HortForum' started by Annell, Feb 24, 2008.

  1. Annell

    Annell Active Member

    Messages:
    47
    Likes Received:
    0
    Location:
    North Vancouver
    I've been gardening most of my life, but one thing that has always confused me is Zones. I just don't get it. Vancouver is zone 9-ish, yes? does that mean, theoretically, planets good for lower numbered zone Don't do well here or Do? I've just never really understood how to use zones in choosing plants and gardening. Can anyone explain it to me like I was a 6 year old?

    Thanks!
    A.
     
  2. soccerdad

    soccerdad Active Member 10 Years

    Messages:
    432
    Likes Received:
    12
    Location:
    Vancouver, BC, Dunbar area
    Many people here know all about this, but I too am pretty ignorant so here it is from another ignorant person's viewpoint.

    North America - and other parts of the world, such as England (but not, I bet, Africa or most of Asia) - have been divided into "zones" by various groups.

    Unfortunately, the groups use different criteria - I think that I now understand some of the differences, but I doubt that you care about what they are - and so you will find that Vancouver is in zone X according to one group and in zone Y according to another group. In particular, the standard American system - which is what is probably used in whatever book(s) you are likely to read - is different from the system that we started using in Canada some years ago, and so a US book will say that Vancouver is in some zone and a Canadian book will say that it is in a different zone. Sort of like a Canadian saying that it is 4 degrees in Vancouver at this moment and a Yank saying that it is 40 degrees: easy to scratch your head in wonder until you realize that they forgot to add "C" or "F" to their numbers.

    I understand that Vancouver is zone 7, but I do not even know what system I am using when I say that. Zone 9 is sure a lot further south than here.

    As for what you really want to know:

    1. Generally, in every system higher numbers mean the place is somehow warmer than places with lower numbers.

    2. A plant that is OK for zones 4-8 is OK in any of those zones, but might die in zone 9 because zone 9 is too hot for it, and might die in zone 3 because zone 3 is too cold for it.

    But I suspect that knowledgeable people might correct just about everything that I have written ...
     
  3. Eric La Fountaine

    Eric La Fountaine Contributor UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

    Messages:
    3,409
    Likes Received:
    149
    Location:
    Vancouver
    The Canadian Hardiness Zones and map are based on the same measures as the USDA Hardiness Zones. Zones are based primarily on average winter low temperatures, but other factors like the length of the growing season, precipitation measures, etc. have been used to make the zones more accurate.

    Vancouver ranges from Zone 7 to maybe 9 in the most protected spots. Proximity to the coast and altitude affect temperatures and the lower mainland (of British Columbia) have a lot of geographic features, so the zones vary a lot over the area.

    Research has determined over the years the average minimum temperature that different plants can withstand. So you want to buy plants that are suited to your environment or take the extra care to get them through the winter.

    Of course the reality of the situation is more complicated. While minimum temperatures in Vancouver may not kill certain plants over the winter, the summer temps may be much lower than their native habitat and they still may not thrive here. Or the winter wet may cause problems--rot and disease. Plants that do well in Vancouver may decline in the summer heat of say Atlanta, even though Atlanta has similar winter hardiness ratings (7 to 8 in the most protected spots).

    The American Horticultural Society has issued a Plant Heat-Zone Map to help gardeners/agriculture determine which plants will survive the summers of different regions.

    Plant Hardiness Zones in Canada

    AHS Heat Zone Map
     
  4. Annell

    Annell Active Member

    Messages:
    47
    Likes Received:
    0
    Location:
    North Vancouver
    thanks soccerdad and eric for those explanations. Not sure where i grabbed the number 9 from, but the rest of it makes a little more sense to me know. I look across the street at my neighbours house that has had full sun all day - his crocus's are blooming - and I look at my yard that has had about an hour - my crocus's have barely pooped about the soil - and I'm thinking he's in a totally different zone from me!

    thank you very much for your answers and the maps!

    A.
     
  5. joclyn

    joclyn Rising Contributor

    Messages:
    2,710
    Likes Received:
    0
    Location:
    philly, pa, usa 6b
    warning! what i'm about to say may confuse you even more!! lol

    annell, what you are seeing with the differences with your crocus and your neighbors is what is called 'microclimate'. things like sun/wind exposure can increase or decrease the basic 'zone'.

    plants grow based on the amount of sunlight they receive - so those crocus bulbs that get more sunlight will grow and bloom sooner than the bulbs that aren't getting as much light.

    as for wind exposure - more exposure due to nothing to break it (bushes, fencing, etc) will create a microclimate that is lower than the surrounding area. less would create a microclimate that is higher than the surrounding area. this difference would be very noticable if you have solid wall around your yard (brick or stone or wood privacy fencing). the little area right where the fence/wall meets the house would tend to be a bit warmer than the rest of the yard/general area because it doesn't get as much wind action. if it's a particularly sunny spot, then you'd probably be able to grow something that is recommended for one zone lower than your basic zone. the plant would have to be prepared for the winter months with extra mulching to protect them.

    for example, i have gladiola bulbs that are supposed to be taken up for the winter in my zone. i've not taken them up - not once in 8 years - and they come back every year. i DO put down a thick layer of crushed leaves for the winter and they are right next to a picket fence, so they are protected from wind. the spot is also very, very sunny for most of the day. so, within that microclimate, they survive and thrive from year to year - even though they aren't supposed to in my zone.

    as you can see, it's not an exact science. very close, definitely. there are always the individual variables that need to be considered, though. so, if you see something that's one zone lower than your location, you may still be able to grow that plant - if you have (or can create) a microclimate that increases the zone rating.
     
  6. Annell

    Annell Active Member

    Messages:
    47
    Likes Received:
    0
    Location:
    North Vancouver
    yes, i understand the micro-climate thing. I'll live in a little climate unto itself with all our shade!

    Thanks for you thoughts about mulching. I appreciate the advice!

    A.
     

Share This Page