Pushing Zone Hardiness in Action

With all the talk of pushing zones this week, I began wondering about people's success stories. I would really like to hear what some of the biggest pushes people have managed on extending zone hardiness without greenhouses. Most of the time, I see people manage one zone lower in number, but not a lot more. Still, I know there are those who have gone way beyond that. I've heard their stories for years now. I even used to work with someone whose tomatoes were almost entirely volunteers each year despite the frosty starts in Pennsylvania. Our own Joseph Lofthouse has been working on varieties to withstand the hardships of his own zone as well.

So how have some of you pushed zone hardiness in your gardens?

This is an extremely interesting question, and something I wonder about all the time. Are you defining zone pushing purely in terms of the USDA zones? Correct me if I'm wrong, these are based on the mean figure of long term extreme low temperatures? Successful zone pushing also relies on mean annual temperatures, and also extreme heat potential.

The really interesting part about this is that some climates differ very dramatically within the same 'zones'. Parts of Northern Florida for example might have the same zone rating as a place in coastal Northern California, but the heat accumulation figures are very different.  And as plant preferences vary so much, a zone pushing in one USDA zone might be very different from one in the same USDA zone in another state.

This is even more extreme using USDA zones outside the USA! I am at nearly 40S latitude, the same distance from the equator South as Philadelphia is North. But my farm is mild enough to range from the USDA 9/10 boundary at highest elevation down to just into zone 11 in the warmest site.  We don't get the cold like Philadelphia, but don't get anything like the heat either.  In my zone 10 climate coconuts are totally impossible as it is far too cold, but many USA zone 10 climates will grow coconuts beautifully. In my zone 10 avocados are easy, but in some zone 10 climates it is so hot avocados are hard to grow without sun protection.

So  we can have zone pushing within the same zone as well as between zones!

I've often thought the only way to really understand zones is to use the USDA minimum temperature figure, and add a mean annual air temperature figure.  I'm in zone 10 with a mean annual air temperature of about 59F (and a small area of zone 11  MAT 60F!),  in USA there are zone 10 climates with mean annual air temperature of close to 80F. Makes the USDA zones a bit hard to use by themselves!

Sorry for the diversion from the OP, I enjoy this stuff!

Ben Waimata wrote:This is an extremely interesting question, and something I wonder about all the time. Are you defining zone pushing purely in terms of the USDA zones? Correct me if I'm wrong, these are based on the mean figure of long term extreme low temperatures? Successful zone pushing also relies on mean annual temperatures, and also extreme heat potential.

The really interesting part about this is that some climates differ very dramatically within the same 'zones'. Parts of Northern Florida for example might have the same zone rating as a place in coastal Northern California, but the heat accumulation figures are very different.  And as plant preferences vary so much, a zone pushing in one USDA zone might be very different from one in the same USDA zone in another state.

This is even more extreme using USDA zones outside the USA! I am at nearly 40S latitude, the same distance from the equator South as Philadelphia is North. But my farm is mild enough to range from the USDA 9/10 boundary at highest elevation down to just into zone 11 in the warmest site.  We don't get the cold like Philadelphia, but don't get anything like the heat either.  In my zone 10 climate coconuts are totally impossible as it is far too cold, but many USA zone 10 climates will grow coconuts beautifully. In my zone 10 avocados are easy, but in some zone 10 climates it is so hot avocados are hard to grow without sun protection.

So  we can have zone pushing within the same zone as well as between zones!

I've often thought the only way to really understand zones is to use the USDA minimum temperature figure, and add a mean annual air temperature figure.  I'm in zone 10 with a mean annual air temperature of about 59F (and a small area of zone 11  MAT 60F!),  in USA there are zone 10 climates with mean annual air temperature of close to 80F. Makes the USDA zones a bit hard to use by themselves!

Sorry for the diversion from the OP, I enjoy this stuff!

I think USDA zones are based on average minimum temperature. So many of your points still stand, just the factor they are looking at is 'what is the coldest it usually gets here'

One of these days I'll get a copy of the sunset zones map. http://sunsetwesterngardencollection.com/climate-zones This has the western seaboard,  but I have heard rumors that this was expanded to cover all the US. We are far from the first people to notice the limitations of the USDA zoning system.

You don't want to know how long it took me to find this https://permies.com/t/61417/permaculture-projects/Climate-analogues-find but the discussion here has stuck with me.  It has a lot of useful information to help find plants from around the world that may be well adapted to your area, wherever that may be.

Climate is definitely more complicated than most people think. I had key limes, black pepper and coffee growing outside along the south-facing wall of my house at the edge of zone 8, which was almost a two-zone push, but I also had cattley guavas (which are much cold-hardier) freeze to the ground forty feet away out in my side yard, due to some sort of frost pocket effect I didn't realize was there until the plants went through a winter.

The best way to learn which plants will grow is to kill a lot of plants. Nature throws seeds around with great profusion. Some survive. I try to approach my gardening the same way. Plant things all over and see if you start to see patterns in what lives where.

It's a lot of fun.