Zones are such a vague guideline. One can have various zones in a small suburban yard, depending on the hardscape, mostly. There can be vast differences in soil temp as well as dry spots vs. wetter areas. Then there's factors mentioned above such as rainfall, elevation, heat/humidity that affect various plants in different ways. A plant has to not only be winter hardy to live here, but it also has to be able to bake at 100 deg & 90+% humidity for weeks at a time, and endure periods of daily rain, or no rain for 6 weeks sometimes.

Also think drainage doesn't get enough credit. If you can keep the ground from freezing *and* from being muddy muck, you can grow so many more things in Z8. Bad drainage + cold temps = death via rot. Good drainage + cold = lots of survivors from Z9/10 plants. A heavy leaf cover bumps the chances up significantly.

There also seems to be some confusion as one gets into the warmer zones (9/10) that I've noticed after moving to where reading such discussions is relevant, then reading 7 years' worth of discussions from people in FL, in particular. Plants that would be evergreen without frost aren't considered hardy by a lot of gardeners down there, they call them 'root hardy,' 'almost killed,' 'comes back after dying for winter,' and stuff like that. Being from OH, anything that's not truly dead is welcome in a garden, perfectly normal, but disappearing for winter is a fairly foreign concept/unacceptable to many life-long gardeners in tropical/near-tropical areas. I *like* when a lot of plants disappear for a few months. Gives me a chance to see so much more clearly, and pull any baby trees especially that were hidden. An easy time to pile on tons of leaves/compost/other OM.

When I first moved to AL, I asked if Persian shield was hardy and got some really weird answers. (They are, BTW, never had one killed over winter, even from the plunge into the teens and ice storm last winter. About a dozen plants, all still alive this spring)

So true, Tiffany. You only need to look at that map of Australia again (in greene's link) to see that the zone in purple has areas on the east coast, humid and moderated by the proximity of the water, and then the huge swath across the middle of the continent that (I think) is mostly desert. So entirely different growing conditions lumped into the same zone just because the average winter low temperatures are similar. Sheesh.

Really, a practical approach for @hazell Deb would be to read around the site a bit on the forums that list the plants you grow, or see growing in your area. Then look at the locations of the people growing those, to get a feel for who you should chat with about your garden. If you don't know names of your plants, you can post pictures on various forums or the Plant ID forum to start with.

One thing N.America and Australia have in common is that many of our gardening ancestors (and favorite plants) came from the same places - the UK and Europe.

I went hunting and found a great climate site!
http://www.hobart.climatemps.c...
http://www.climatemps.com/coun...
http://www.seattle.climatemps....

They say that Hobart, Tasmania, Australia is Köppen-Geiger classification: "Cfb". \
That's close to my coastal PNW Koppen zone "Csb" except that we have dry summers. Maybe my summers are hotter and winters colder.

Are you overcast and drizzly 8-9 months of the year?

Koppen Cfb - Maritime Temperate or Oceanic. Changeable weather. Often overcast. Cool summer, mild winter.
Köppen-Geiger Csb: dry-summer subtropical "Mediterranean"

"Hobart, Tasmania has a marine west coast climate that is mild with no dry season, warm summers.
Heavy precipitation occurs during mild winters which are dominated by mid-latitude cyclones.
Seasonality is moderate."

They also mention something new to me: the "Holdridge life zones system of bioclimatic classification". They say Hobart is in or near the "cool temperate moist forest biome".

Read more: http://www.hobart.climatemps.c...

>> Also think drainage doesn't get enough credit.

Agreed! In my yard that's the major factor, even more significant than shade. Before amending it, not even weeds do well on my clay.

Drainage, shade & exposure, elevation, insect pests and pathogens (and probably mulch and snow cover) all make huge differences.

I think one reason I enjoy growing things is that, even if science "should" predict everything about gardening, in reality every single square yard is so complicated that teams of PhDs could labor for years trying to explain everything. And they would still be stumped by green plants without a single neuron.

P.S. here's an "Idea" about the microclimates in one backyard:
http://garden.org/ideas/view/P...

Hi and a big THANK YOU to everyone.
There have been a lot of interesting discussions that have evolved here from my question and many relevant points made, especially how one yard/garden can have so many different "zones".
Again, all!

RickCorey said:I went hunting and found a great climate site!
http://www.hobart.climatemps.c...
http://www.climatemps.com/coun...
http://www.seattle.climatemps....

They say that Hobart, Tasmania, Australia is Köppen-Geiger classification: "Cfb". \
That's close to my coastal PNW Koppen zone "Csb" except that we have dry summers. Maybe my summers are hotter and winters colder.

Are you overcast and drizzly 8-9 months of the year?

Koppen Cfb - Maritime Temperate or Oceanic. Changeable weather. Often overcast. Cool summer, mild winter.
Köppen-Geiger Csb: dry-summer subtropical "Mediterranean"

"Hobart, Tasmania has a marine west coast climate that is mild with no dry season, warm summers.
Heavy precipitation occurs during mild winters which are dominated by mid-latitude cyclones.
Seasonality is moderate."

They also mention something new to me: the "Holdridge life zones system of bioclimatic classification". They say Hobart is in or near the "cool temperate moist forest biome".

Read more: http://www.hobart.climatemps.c...

Sorry, I missed this. Great investigative work. But. NOoo... Hobart is definitely not overcast and drizzly for 8-9 months of the year. We just perpetuate that image to keep the (present company exclude, thehazell!) mainlanders away! Dun know where the statistics for those sites could have been cooked up.

Thanks, Della.

"In theory, theory and practice are the same.
In practice, they ain't."

That's strange. I have a friend in Hobart who actually saw the sun once.

Gleni said:That's strange. I have a friend in Hobart who actually saw the sun once.

A boastful person of questionable veracity!

Probably a Launceston Gully Person -rising from the 'Foggy Moors'