If the altitudes shown are correct, I highly doubt that it is tropical. wiki- info-Picea-Chihuahuana

ETA: Here is a link to another discussion about this tree: GardenWeb:

Thx for the links and the info. I wonder if high-altitude areas of tropical or subtropical zones experience seasonal variations in temperature though

Oh, and there are mountainous areas in the Durango and Chihuahua provinces that have 7a to 8b USDA temperatures. See Map:

Most Mexican conifers are from altitude. PIcea chihuahuana grows well here in 9b.

' I wonder if high-altitude areas of tropical or subtropical zones experience seasonal variations in temperature though'

I've seen snow on the mountains of Hawaii. :)

Absolutely. There are multiple biomes that exist at altitude in latitudes where the flatland flora is completely different. See cloud forest for example.

The central and southern stands are at an everage elevation of 2675 m, the northern stands at 2325 m (Ledig et al. 2000). Their native climate is continental and among the coldest in Mexico; at Creel, Chihuahua, the temperatures range from an average January minimum of -5.6°C to an average July maximum of 26.5°C, and climate is summer-wet with average monthly rainfall 16 mm in April and 166 mm in July.

http://www.conifers.org/pi/Picea_chihuahuana.php

Thanks for the info guys, so if it grows well in 9b would it be worth a try ?

What are your complete environmental conditions?

Picea chihuahuana can handle heat better than most spruce, but I wouldn't mistake being able to "handle" it with "growing well." They can survive in the United States as far south as southern Georgia, but their growth can hardly be considered vigorous. You will almost certainly never see a 20 foot tree there, much less a 100 foot one. And that's in zone 8b, not 9b.

Here in 9b there is a lovely specimen at Quarryhill Botanical Garden - gets very hot there in summer (90s) but it is bone dry. Exactly the opposite of its native habitat. It is in partial shade, outside of the garden gates, since it is not Asian.

I suspect the problem down here is both the heat and humidity. 80 degrees and rainy or 95 degrees and dry are much different beasts than 95 and humid. And 75 at night, too!

But look at its native habitat - hot during the day (80) and summer wet. That's closer to Georgia than Glen Ellen, CA, at 90 in summer with bone dry air. And the one at QH is gorgeous, although it is the prickliest conifer I have ever encountered.

I'm not sure I'd quite call 80 degrees during the day "hot," at least not compared to the 95 that is common in south Georgia. Also, at elevation in Mexico and in the low humidity areas of inland California, one typically sees radiational cooling at night that surpasses the cooling we see in the muggy Georgia summers.

But don't just take my word for it. John Ruter of the University of Georgia has been growing Picea chihuahuana for 10 years in Tifton, Ga (zone 8b). It's size after those ten years: 2.9 feet high and 3.9 feet wide (see his book "Landscaping with Conifers and Ginkgo for the Southeast"). That's barely eking out an existence. I suspect the original poster will have trouble in a tropical zone 9b.

But don't you think it's odd that it seems to do so well in our 9b with dry summers, when that is very different from its own climate? I wonder what the limiting factors are.

7500 ft. in NW Mexico is definitely closer to coastal California than southern Georgia! That is the lowest elevation reported for the range of this species. The nearest large city, Chihuahua. has summer nights of 66F at an elevation of 4600 ft...but that's with daytime highs in the low 90s! In the deep south of the US, even a midsummer night of 66F would be considered a cool one. At the most conservative, adiabatic lapse rate would suggest night temps at 7500ft. of about 57F. But probably lower. Mexico City is much further south, no higher in elevation, and has no month with a nightly low higher than 56F.

(summer night temperature is a pretty good stand-in for average dewpoint, since that statistic is often not available. Dewpoint is a better indicator of what humans consider 'humidity' than relative humidity.)

So...it comes from a place with much lower dewpoints, cooler nights, and a somewhat steeper drop off in nightly temps, than the US SE. It's actually surprising it grows in that part of the southeast at all, I would have guessed you would have to be up north of Atlanta at 1500' or so, where rhododendrons become somewhat common. Also, interesting that it just grows incredibly slowly**, instead of dying as I can attest frequently occurs with low summer dewpoint plants in a high summer dewpoint climate! Even if the climate in its native range is 80/57 with 6 inches monthly of rain in summer, that's closer to this: https://en.wikipedia.org/wiki/Santa_Rosa,_California#Climate than to this: http://www.sercc.com/cgi-bin/sercc/cliMAIN.pl?ga1340

** that being said, some conifers just seem slow when they are small, period. My Pseudolarix was going at about 2 inches a year before it died in a watering neglect incident :-<

Yes those warm nights can be a problem for sure, which Ruter and Cox make a point of in their book, and I guess the reason that most Abies don't thrive in the SE. Dewpoint has always confused me...

When you get 50 miles North of "Cox Arboretum" and a few thousand feet higher, ones palate can acquire a different taste readily!

Johnny

It's easier to start with relative humidity. Relative humidity means: "relative to the temperature, how much humidity (water vapor) is present in the atmosphere?" Why relative to temperature? Because at warmer temps, the atmosphere can hold more moisture.

You can see at 100% relative humidity, there is twice as much water in the air at 32C as at 20C. 30 grams per kg instead of 15 grams per kg.

Dew point is, as the graph indicates, this temperature of maximum absolute humidity (the amount the atmosphere can hold in actual grams per unit area) - meaning the point where the relative humidity is 100% and no more water can be held without rain starting to form. One should think of the atmosphere as a system governed by natural rules, and that system must return to equilibrium. Rain or fog are the processes that shifts the equilibrium back to this chart. You can't have more water in the atmosphere than what is indicated here. (nope, sorry, cheesy motivational speakers - nobody can give 110%, ever!)

In maritime climates, relative humidity can of course be very high - near 100% when it's raining, but it's still not very uncomfortable because the dewpoint is down around 17C/62F. (and usually isn't that high in a place like Seattle.) OTOH, in the southeast, dewpoints from 70-75F or higher, are not uncommon. Even though in the afternoon on a very hot day, RH might drop to 50-60%, there's still more moisture in the air than a maritime climate where the RH is 100% but the air temp only 17C. (staying with degrees C because the chart is in C!) Notice on our chart 98F/37C at 50% humidity (green line) - very possible in parts of the south in summer - has much more absolute humidity, i.e., the actual amount of water vapor in the air - than the PNW during a May rainfall, which would at most be maybe 18C at 100% humidity. (red line)

source https://en.wikipedia.org/wiki/File:Relative_Humidity.png

It might seem strange that such a smallish increase in DEWPOINT from say 62F to 75F feels so awful to us, but one has to remember our personal biological aka physiological system is pretty fine tuned as well, to operate at 98.6F /37C. Clothing is good at preventing the release of body heat. The south would be more tolerable if one were allowed to wear bathing suits to work...you are, in a sense, in a bath of very warm water(!)...but it's probably a good thing that isn't the case. (that being said it's absurd to me that the eastern US from NY & Chicago downwards, didn't adopt the summer dress of Bermuda! i.e. men being able to wear short dress pants and shirts)

Whew this is complicated! Too late here for me to process. But thank you for the info and I will read in the morning when I can focus. This appears to be important and not well understood by the masses.

I have tried it here in Orlando, FL (zone 9b/10a) along with a couple Mexican Abies and they did not make it through one summer. Even Abies firma barely survives. It is too hot too long and too humid. The lack of cooling severely stresses the plant and the high humidity and daily rainfall expedites fungal problems.

Good to know what their limit is, eric.

So the common claims of sellers to be good to Z-9 could be looked at as pushing it, unless extra care is given as it has in an arboretum.

In it's native habitat, it is found most commonly on steep, north facing slopes, which could be a determining factor on how well it flourishes, taking into account root exposure to sun etc.

And once again, paying attention to the heat/summer part of the equation, not just the cold/winter (which is what USDA zones do). As someone in Zone 9b, I can tell you that I have more issues with summer than winter hardiness. I suspect many of the folks in the SE have similar issues, albeit for different reasons.

"So the common claims of sellers to be good to Z-9 could be looked at as pushing it,"

Nope, should be looked at as the realistic limitations of the USDA plant [cold] hardiness zone map. (i.e, they really should have added the word cold to the official title, since laymen could be confused as to the strict meaning of the term hardiness) Which is all it is. It isn't an overall plant adaptability map by any means...which is what Sunset zones are trying to be. Zn 9 in FL is very different from zn 9 in Norcal. (to restate what Sara said LOL...)

Dave, the USDA range of Picea chihuahuana is Z7-Z9, with some sources saying Z6-Z9. Regardless, the Z9 is the warmest end of it's range, not the coldest. So I guess it can work both ways with zone pushing.

I could be wrong but I think the OP's USDA zone is something like Z11 or maybe even higher (tropical anyways) and a plant with a high end of Z9 won't survive there or at least not flourish. But maybe we're talking about two different things here. :)

" As someone in Zone 9b, I can tell you that I have more issues with summer than winter hardiness."

Sara hate to make this veer off topic, but curious as to what you meant here exactly. In one of my epic 'battle threads' from long ago, I pointed out there are far more plants from warm summer temperate climates that can tolerate cool (or in your case, maybe just drier and thus cooler at night) summer climates, than vice versa. Which is of course true, and there are obvious paleo-geographical reasons for it. I know you have different soil but the cool nights at Sonoma Hort, for example, let him grow cinnabarinum subsection rhododendrons. By "summer hardiness" are you just referring to the need to water things from moister climates like Asia? In fact, if one can afford to water ad libitum, Sonoma county 9b - which I assume is where you are, roughly, strikes me as the best climate in the USA. "Winter mild" enough to grow desirable subtropicals like citrus and aloes, "summer mild" enough for things that want cool nights like the aforementioned Himalayan rhodies, but seasonal enough for pome fruits, classic temperate perennials, etc.