It is not really the zone that is of issue - that only relates to winter cold tolerance - but rather the conditions that exist in summer that may be a limiting factor. White spruce prefer cold winter climates with cool summers and do not tolerate summer heat and humidity well. Chances are if not readily available in area nurseries, it's not a great choice for your location.

Thanks gardengal48! That’s what I was afraid to hear. Oh well, I guess I’ll have to find something else.

Thank you alley_cat_gw! That’s encouraging! I LOVE the shape of your tree! I want one!

I have one in my 7b/8a garden in South Carolina. It lives but hasn’t grown much in all the years that I have had it.

Thank you scpalmnut! I believe it! We used to live in South Charlotte, right on the SC line, and it was HOT! While our summers are hot here too, we have a FEW more mild days than we did there. Is yours in full sun or part shade?

my z5 MI.. is as hot.. if not hotter than some z7 or 8 ... i dont think that alone is the issue ...

it was suggested to me.. it might be more a a night humidity thing ... and it might have to do with diseases that thrive in high night humidity ...

and of course.. in my ground freeze z5 ... you all dont know what winter cold is.. lol ... so it isnt that ...

but it might be something about actually being cold enough.. long enough for some conifers.. certain chill hours like some other plants.. but i dont figure that is an issue with a tree rated to z8 ...

ken

What some seem to have trouble grasping is that the USDA hardiness zones ONLY rate a plant's tolerance to winter cold. There is no point in presenting plants with a hardiness range......if the tree is hardy to zone 2 (only measuring winter cold) then of course it will be hardy to a higher zone!! There is nothing in the hardiness zone designation system that evaluates the plant's suitability in that zone outside of winter cold tolerance......nothing!! It is only just confusing and misleading to offer plants with a hardiness range as it gives the impression that if it can survive winter in that climate, it can survive all the other climate issues associated with that zone outside of winter temperatures. Which is patently not the case.

Good explanation; I think I get it. Still, heat & humidity limitations are real barriers to some woody plants long-term success. I believe a former poster, who went by Pineresin, made this argument using the native Balsam fir as an example of a conifer that suffers from heat and humidity, combined with a lack of evening soil cooling. Is there nothing comparable (and reliable) to the USDA’s hardiness zones to guide gardeners who long for balsam fir and paperbark birch in their southern garden?

" Is there nothing comparable (and reliable) to the USDA’s hardiness zones to guide gardeners who long for balsam fir and paperbark birch in their southern garden?"

macckia - isn't that basically what the "sunset" zones are? Do they do sunset zones for the whole country or just the western US?

"macckia - isn't that basically what the "sunset" zones are? Do they do sunset zones for the whole country or just the western US?"

Lane, I know nothing about "Sunset zones," other than what I've heard mentioned on GW. I generally don't have to concern myself with a plants tolerance of heat & humidity. ;)

I just looked through several nursery tags from 2017-2019 purchases, and most list a lower (cold) and upper (heat) zone where they're recommended. Some (Proven Winners and Monrovia) list USDA with the zone range, implying both upper and lower limits are USDA-based. Others (Bizon and Carlton) simply list the zone range without reference to USDA. Iseli's tag lists only the lower (i.e. cold hardiness) zone.

Unless the tags have the AHS heat zone designation as well as the USDA hardiness zones (and will be clearly labeled as USDA and AHS zones) then there is no valid upper or heat zone. USDA zones do not (and cannot) measure summer heat!! There is no such thing as a hardiness "range" - it is either winter cold tolerant for your area or not so should only reflect the lowest zone the plant can be expected to survive.

And yes, there are Sunset zones for all of the US. But most gardeners outside of the west coast are not aware of them and I am not aware of any wholesale growers that tag with them.

I'm in zone 7b and have no issues growing my Weeping White Spruce. I've had it for 6 years. I see other Weeping White Spruces in front of houses in the neighborhood and they look fine.

I'm also in 7b, and Picea glauca will do okay for a few years here before decline seems to set in. All of the local nurseries stock 'Conica' because of the Christmas-tree shape, but you just don't see very many large(r) ones in people's yards. Picea abies does better, but it is far from bullet-proof. If you want the best option for a weeping spruce in zone 7, try Picea orientalis 'Nutans' or Picea omorika 'Bruns pendula' or 'Pendula.'