I would be conservative about cold hardiness. There is a good chance that we will enter global cooling around 2015 depending on the sun activity. We might move back to 1990s chart in 10-15 years. The sun has been very quiet for quite a while.

Information is not all the same, because not all the trees are exact replicas, then you add the mix that all climates are not exactly the same if even same hardiness zone. I have even had clone trees within feet of each other, and one died and one lived fine. So a lot comes into play.

This specific tree from what I have read is quite variable, so just depends what seedling you get. Would be easier to just grow them out from seedlings, then the strongest survives. I remember when seneca hills nursery was still around, they had a cold hardier one selected of this species.

Your hardiness zone...
The differences in different hardiness zone maps is mostly due to the time periods which were evaluated to make the maps. Older maps (like the former USDA map which was produced from data that is now around three decades old) are basically out of date. Things have changed and the trend, in most areas, is warmer weather. Some maps, like the Arborday map, are a little more current but still not always totally representative of current conditions. Even the new USDA map uses data that is too old to accurately reflect current conditions in many area. Use the Arborday map or the new USDA map to get starting point, but do realize that they have their limits. They can't tell you much about microclimates, they don't account for unusually cold or warm years, and they aren't completely up to date (even the newer ones).

Differences in ratings among different nurseries...
Lkz5ia pretty much covered this, but I will reemphasize that climate is very different in different parts of the country, and so what is true in a certain zone in one part of the country can be very very different in that same zone in another part of the country. Hardiness zone ratings are just part of a much larger formula, and the other factors can greatly influence those ratings.

global cooling around 2015...
This appears to be an idea that was never taken very seriously (even as it was being thrown out as a possibility), was later shown to be highly unlikely and not based on solid science, and then picked up by a few politically motivated people to push their agenda no matter how debunked the idea became. Kinda reminds me of the people that think the moon landing was faked, but maybe not quite as nutty.

On the other hand, it never hurts to be conservative in what plants you choose to grow. It may not be as fun (some people get a huge kick out of pushing zone limits), but it is obviously safer. I usually keep a one zone buffer on both sides (colder and hotter) for plantings that I want to be around for a long time. Here in my zone 7, most of my trees are considered hardy in zone 6 to zone 8, at least. This is not to say that you shouldn't be daring, just as long as you realize the ramifications of your choices. Things can always change and weather can always be quirky/anomalous.

Musser forests in Indiana Pa has me in zone 5 and Arbor day has me as zone 6-7. I am zone 6. I am close to the mountains, about 7 miles away. I guess if you look at a map you may think I live up in the mountains, where it is always around 10 F colder. if you are close to alot of concret buildings and bodies of water, maybe you are warmer than somewhere close to you, or colder at higher elevations.

Brandon,

We will see in 2015 or so.

In the meanwhile, go read Don't sell your coat by Harold Ambler, Delinquent Teenager by Donna Laframboise to get you started...

By the way, CO2 causing warming theory is just as bad as saturated fat/cholesterol consumption causing heart disease. All from junk science...

I use to be zone 5 and numerous years ago they changed me to zone 6. I plant almost all zone 5 plants. I have put in a few zone 6 but they are shrubs that wouldn't cost me a lot to take out if they fail. Now a tree, I'd hate to grow it on for 10 or 15 years and have it fail, but sounds like Forest Farm is conservative and it might be why they use a higher zone to cover the possibility of zones changing back at some time. Actually quite a good business policy I think. So they are saying 6 but you are a 6 now also, so bet you'll be just fine.
Cher

i work under the presumption ... of the decade or century storm.. or season ...

even if you go straight z5 .. being in z5 ... sooner or later.. a real z4 winter will slip in.. and you will lose reliably hardy stock ...

so its all irrelevant regardless ... that is why they are called decade/century phenoms ...

which means.. here.. that you are zone pushing.. you know it.. it doesnt matter if we ask the sources to vote on it ... and as with all zone pushing .. micro climate will rule ...

on my former horse pasture.. i could not push a 6 .. no matter what the USDA says.. because of the winter winds ... as i dont think min winter temp is the sole variable to a plant ability to overwinter..

yet up on the side of the house.. opposite the prevailing winter winds.. i can push a 6 with variable success ...

good luck with your experiments ...

BTW.. the further south the grower/producer is.. the more they tend to not understand colder zones.. and frankly tend to be very generous on zone claims on their tags ....

ken

Thank you for all of your responses. I really appreciate everyone's pov on this. I had absolutely no idea we should buffer our tree/shrub choices by one growing zone.

I truly believe (fwiw) that I am a zone 6. Im 10 minutes from Lake Erie, and I live on a somewhat large lake myself. I'll plant this tree in the front yard, which faces North, to protect it from the prevailing S/SW winds. Our front yard gets a ton of sun.

I can only roll the dice and pray that because I'm on the cusp of zone 6, and this Golden Raintree is good to 5, that if we have a cold snap it doesn't go all the way down to zone 4. I guess we shall see......

that wasnt my point .... the point was that stuff happens.. even with stock that is thought to be reliable in any given zone ... mother nature really lacks a sense of humor when she has a bee in her bonnet ... to mix a bunch of metaphors ....

most wont care about a z4 in my example.. it just wont matter... but something though secure.. might not make it ... and its usually the one i prize most ... lol

anyway .... i recall once.. discussing this with a very large wholesaler.. complaining about another supplier.. and wondering why the bad labels .. like you ...

and his best guess was that supplier A ... had a quarter million tags printed up so many years ago .. and they will be damned.. if they arent going to use them up.. before they print another batch .... and i bet some of this is behind bigboxstore labeling problems ...

all speculation.. who knows ...

ken

I'm not sure how the number of years ago a supplier had their tags printed up would make any difference, but maybe that wasn't the point.

I use a "buffer" only as a way of having a degree of safety against that very unusual weather event (as Ken described). Not all my plants are "buffered", but I make that decision when choosing the tree. Some specimens are "toys" (no buffer) and other are relatively permanent landscaping components (buffered).

There is one big box store hint: blue and white, that you can't trust their zones for their plants. Most are correct but not all. Just my experience.

See, I thought the zones themselves were already quite full proof and buffered in their own right. I though the temperatures within each of the zones were broad enough to handle any usual weather events for that zone.

I personally don't want to "push" a zone for the fun of it and take my chances. Every one of these trees I want to see grow and thrive, and live to their full potential. None of them are "toys".

But in context, lightening or some unknown disease could take them out long before the "weather event of the century", so like anything, there's no guarantees for our trees even in the best of circumstances, and in the securest of zones.

Climate always changes.

Here is a link that might be useful: Climate always changes.

In my opinion, Forestfarm is consistently very conservative in their zone ratings. If they propagate Goldenchain tree from their own stock, they may also be allowing for the possibility that what they're selling may actually be less hardy than trees from somewhere else. There are plenty of other nurseries which tend to be wildly optimistic. Forestfarm's approach is understandable in that it provides a margin of error and, ultimately, better customer relations.

Hardiness zones are a general guideline, nothing more. Within a half-acre back yard there can be 3 or more growing zones/micro climates.

The CO2 talk probably deserves its own thread. All I know is the climate zone maps are pushing zones further north. Blame it on man made urban heat islands, CO2 or the activity of the sun god.

Go conservative in your plant hardiness calculations. Someone selling something has money to make from claiming a zone 3 hardy southern magnolia or whatever. I even read a car magazine which claimed the Tercel was superior to the Prism. So use common sens.

Actually, for much of the east the climate zone maps are *not* pushing zones further north. And the places they are, the locals are having significant issues with that.

A more accurate assessment is that the immediately previous zone map was skewed cold. The latest map is an attempt to correct that. While all the maps list me as 5b, in reality I am another Pinatubo away from -30. Don't even think about another T*B@.

The new USDA map is way too conservative for my part of the country. For instance, Knoxville is located in zone 7a, but our last couple of decades have averaged closer to high 7b or low 8a. Temperatures are definitely on the increase here. Deep snow-cover used to be the norm in this area. We haven't seen a decent snow in many years now. The kids these days look at us strange when we talk about how it used to be years ago; the younger generation hasn't seen weather like was common decades ago.