USDA Plant hardiness zones and how does it affect me?

Howdy,
This is my second attempt to post this today. I guess it got lost. Anyway it wasn't an in depth post so I'll retype the gist if it.
My question stems from reading others' posts and often seeing the plant hardiness zone in their location information.
We're somewhere between 5b  and 6a in the mountains of northern New Mexico. I'm not certain because of this rugged terrain to what degree the zones matter to us, or for that matter what are the specific differences between 5b and 6a?
I'd really love to know what the zone means to you, where you are and how you use the information to help you grow plants.

Hi! We are also between zone 5 and 6. That means it gets so cold and for so long the ground freezes here most years. That means we get enough chill hours for most things that require chill hours, but we can't grow pomegranates in the ground, or other things that can't stand being frozen solid on and off for about 4 months a year. Though, since we have enough well lit indoor space,  I generally say there's about 2 things you can't grow here: coconuts and dates.

We were zone 9b, recently they changed it to 10a. I find this information to be very incomplete. We don't always get a frost, but our climate is much milder than others in the same zone. We also don't get much heat, so comparing to others in the same zone, often Texas, the growing conditions are vastly different. Things like tomatoes and peppers are very slow to ripen here. I find zone information to be most useful in regards to trees, like Amit said. Do I have enough chill hours or for others, will it survive the frost?

I'll admit that I understand very little of this whole climate zone thing. In Europe we don't refer to it much, and people seem to use different systems depending on the country they live in?
In a topic about Elephant Garlic and how hardy it was I mentioned that this garlic had a hard time surviving my winters and I said I was in climate zone 8, but that I doubted whether our winter storms were factored in. I got this reply from someone:

The northern Netherlands is definitely under a different scale for hardiness zones than the USDA hardiness zones, as USDA zone 8a never falls below 10° F. The northern Netherlands gets lows well below zero, and would be closer to USDA zone 3, depending on your location relative to maritime temperature influences. Hope that helps everyone compare apples to apples.

Zone 3, really? That sounds a lot colder than were I really am! But I'm a sceptic of the system anyway. At best it's a guideline on how cold your winter gets and what'll survive and what not. It doesn't tell much about what you can grow in the summer, and in summer I grow lots more things than in winter. Who doesn't?
Something like a heat zone system I would find at least as useful. I know it exists, but gets rarely used.
For the time being I will not mention any climate zone number with my profile, as I don't think it'll be very helpful.  

I'm also in an area where the USDA zones don't mean much. Our 600 acres rises from sea level to 1000" elevation, and changes from a USDA 11a right up to 9b. But I'm at close to latitude 40S, and the temperature very rarely hits 90F in summer, and can go for years between night dropping below 40F. The summer heat accumulation is more like Canada than the South Florida zone 11a suggests.

I see a logical way around it though, use USDA zone (which records only the one factor, the mean figure of the extreme yearly low) with the annual average air temperature. When you do this, you get a good picture of the temperature range in any area (rainfall, sunshine etc are a different matter!). Example, most of my farm is in USDA 10b, the same USDA zone as Miami. Miami has a long term average temperature around 77F. Immediately we know Miami is an essentially tropical climate that occaisonally gets coolish in winter. My climate is USDA zone 10b as well, meaning the extreme low is reasonably mild. But the long term mean air temperature is about 59F. Immediately it is obvious that it is a cool climate without extremes of temperature. I think San Francisco is zone 9b or 10a, mean annual air temperature of 57F, so pretty similar, but with slightly higher frost potential.

One interesting thing when comparing zones for plant growth is that some plants need heat, some don't. So a climate 10b tree like a coconut palm can be grown easily in Miami but will not even survive an entire summer here. Another zone 10b tree like a banyan fig can grow easily in Miami but also grows easily (but significantly slower) here. The banyan is a good example, as it becomes hard to grow as you go further north in Florida. 8b and 9a areas of Florida are still far warmer than my climate, but those places cannot grow banyan trees due to the occaisonal cold night,  I can. So the USDA zones are designed for continental USA where they work well, but are still applicable to other areas if we take into account heat accumulation factors.

Another example of the difficulty in climate zones; 30 years ago New Zealand researchers were attempting to find suitable genetics for a pecan trial here. The two most important factors are winter chilling and heat accumulation. The parts of the pecan natural range that have winter chilling anything like the NZ climate where only the extreme southernmost part of their natural range, but these provenances required far more summer heat than we get and failed to fruit here.  The extreme north of the range provided climates with cool summers comparable to ours, but these selections failed totally here without enough winter chilling. There was talk of hybridsing to try to get a more neutral pecan tree, but there is still no pecan industry here. We've got pecan trees on our farm, at least the foliage is nice, there has never been even nuts.

J Grouwstra wrote:

Quote: The northern Netherlands is definitely under a different scale for hardiness zones than the USDA hardiness zones, as USDA zone 8a never falls below 10° F. The northern Netherlands gets lows well below zero,

Zone 3, really? That sounds a lot colder than were I really am!

I think someone forgot about Fahrenheit vs Celsius.  

Possibly. Although The Netherlands does get lows below zero also on the Fahrenheit scale, but not much lower than something like -15°F. That would already be an exception. Factor in the wind chill and we'll get there more often, and it does get quite windy in a completely flat country.  

But I believe this USDA climate zone system works less well the more maritime you get. Somewhere like Scotland is very maritime, especially near the coast, where most people live. Frosts are rare here, often you can walk in t-shirt in the middle of winter. I think it's tagged as zone 9? But the summers are lousy, just a bit warmer than winter. Can't grow many heat-loving things, for that you're probably better off on the Canadian prairies, with a much lower zone number attached to them. You just can't catch a climate with one single number.

Honestly- it's worthless. Only thing you should use it for is to weed out plants that WILL NOT survive -20 (or what ever your hardiness says) if you expect to keep them for a long time. However, WHERE is -20? Out on the open field? Yeah. What plant zone do you have in front of south-facing rock face? Probably 600 miles further south. What plant zone do you have on a south facing slope? 600 miles south. On a north facing slope? 600 miles north. On a level plain with wind that has no obstructions for 100 miles to blow? What they said you have. What happens if you put a foot of leaves over a plant and then it gets to 20 below? It'll probably stay warm enough to survive.  

Everything is relative. You do know about the plant heat zone map as well don't you?

Awesome thank you all for these helpful comments. Sometimes and with somethings I feel quite dull, plants appear to be one of those things. No wonder I had so much trouble growing things like food. Apples for example do fantastic one valley to the north. Peaches grow down in town just fine. I always thought we were cheated in that regard. This is one of the reasons I built a greenhouse. Okay with USDA zone  information taken with a grain of salt  I shall begin learning permaculture practices to hedge my planting bets.
Our home is on a hill top, with a ~8° slope north and south. Manicured Ponderosa Pine forests interface with the south and east  sides of the house. We moved a 1959 mobile home up here 20 years ago and have had a food garden on the northeast  side and flower gardens on the south sides. The last of the mobile home was demolished one section at a time as we replaced the kitchen with a frame structure  and finally removed completely last Summer. I'm not sure exactly how the food garden came to be on the north side of the house, but it gets good Summer sun there. Recently I've removed that garden and this Summer I'm converting the area to permaculture practices.
I've started a huglekultur berm. I'll no longer turn the soil over with a shovel and work to keep the soil alive. I will continue to read here and ask questions.
For example; is there a list of things to do to convert this semi-arid area to productivity? Swales, hugles, irrigation, gray water.  I have a pond on an arroyo which thanks to an unseasonable rain is currently full of muddy water.  
Grateful for you guidance,
Brian Rodgers

Brian Rodgers wrote: is there a list of things to do to convert this semi-arid area to productivity? Swales, hugles, irrigation, gray water.  

Bill Mollison (the main founder of permaculture) wrote a book called Permaculture A Designer's Manual, often referred to as Mollison's big black book. There is a whole section on Dryland Strategies (Chap 11, Pgs 308-410.) The book is generally not cheap, I think I had to pay 80.00 for my copy, but it is WELL worth it if you are a reader. It's all the design principles that are taught in the PDCs (Permaculture Design Course.) If you are more a class taking type, look for a PDC in your area, it will probably cover a lot of local strategies. I never realized till just now there a whole forum on Permies just for The Design Manual! Permaculture A Designer's Manual Forum

Yes, swales will help, especially if you have enough runoff that it's ponding, their job is to hold that water still as it soaks in where you want it. Adding organic material to help build up the soil's water carrying capacity (which is basically what a hugel is) will help hold what you get. Grey water use is always good in dry areas, it's a shame to waste it, and irrigation is more a last ditch technique if you still can't get enough water to hold in your soil. Holding the water in your soil is always better than irrigating. When I lived in NM I got very good at drip irrigating, the problem with that being it doesn't really build up the soil moisture content as much as I wanted, I'd flood irrigate, then drip for a month or so, then have to flood again. The drip was specific for the plant, but the surrounding soil wicked a lot of it away.

AS far as what plants, the other thing I did was create microclimates. I had things growing that "you can't grow that here!" Oh. Looks like it's doing fine! Microclimates are worth learning about. I was in zone 8b (dry) and not a lot grows there unless you get creative.

Pearl Sutton wrote:

Brian Rodgers wrote: is there a list of things to do to convert this semi-arid area to productivity? Swales, hugles, irrigation, gray water.  

Bill Mollison (the main founder of permaculture) wrote a book called Permaculture A Designer's Manual, often referred to as Mollison's big black book. There is a whole section on Dryland Strategies (Chap 11, Pgs 308-410.) The book is generally not cheap, I think I had to pay 80.00 for my copy, but it is WELL worth it if you are a reader. It's all the design principles that are taught in the PDCs (Permaculture Design Course.) If you are more a class taking type, look for a PDC in your area, it will probably cover a lot of local strategies. I never realized till just now there a whole forum on Permies just for The Design Manual! Permaculture A Designer's Manual Forum

Yes, I read a lot when I was younger, then I turned into a workaholic, letting reading fall to the wayside as I dealt with more pragmatic things, such as reading technical manuals. After having to learn about health this year I read Tom O'Brian's Autoimmune Fix The autoimmune Fix and found that I really missed reading. I subscribed to GoodReads in the hope that I might parlay my earlier love of Sci-Fi into something new, but nothing was really ringing any bells. Perhaps this is what I wanted? Thank you Pearl.  

Pearl Sutton wrote:
Yes, swales will help, especially if you have enough runoff that it's ponding, their job is to hold that water still as it soaks in where you want it. Adding organic material to help build up the soil's water carrying capacity (which is basically what a hugel is) will help hold what you get. Grey water use is always good in dry areas, it's a shame to waste it, and irrigation is more a last ditch technique if you still can't get enough water to hold in your soil. Holding the water in your soil is always better than irrigating. When I lived in NM I got very good at drip irrigating, the problem with that being it doesn't really build up the soil moisture content as much as I wanted, I'd flood irrigate, then drip for a month or so, then have to flood again. The drip was specific for the plant, but the surrounding soil wicked a lot of it away.

I hesitate with sway construction as with this relentless rain we're getting, the forest floors, pastures and meadows are packed with plants which I'd hate to dislodge, them. We've been doing slash piles and berms here for decades and they really do work, so maybe that is good enough for now? I do want to incorporate the forest into our yard and gardens. Out in the pasture I'm looking for good deals on Vetch I really like the idea of adding nitrogen fixers to the soil. So far it seems pricey. I also need to learn how to broadcast seed in an established pasture.

Pearl Sutton wrote:  
AS far as what plants, the other thing I did was create microclimates. I had things growing that "you can't grow that here!" Oh. Looks like it's doing fine! Microclimates are worth learning about. I was in zone 8b (dry) and not a lot grows there unless you get creative.

Micro climates, yes that sounds like the ticket.  Great I'll keep reading and I'll also look for the book you mentioned.
Thank you.

IMHO swales are always a good thing. I think it was elsewhere on here that described what a real old growth forest looks like. And others on here have complained about that same problem.

An old growth forest floor is NOT level at all. Every time a tree falls it makes a hole. Multiply that x 1000 and you get a whole pile of swales. Anything you can do to redirect the water from running into the sea and running into your aquifer is going to be a good thing. Someone also posted on here that when they fixed their swales the spring down the hill started running again.

The simplest swale is a dead furrow.