The Roezl originals have proved hardy in Britain, but that's mostly zone 8. As it comes from a long way south (18-19ðN), I'd be dubious about its ability to take zone 6/7 even despite its high altitude origins.

Resin

Thanks Resin, I'm sure some provenances are hardier then others but finding that special source would be quite the challenge!

Johnny

On a side note; two other Mexican conifers seemed to come thru unscathed, Abies vejarii and Picea martinezii all look good after experiencing 0 F/-18 Celsius.

Johnny

Not suprising those last two, they're from a lot further north (24-26ðN) - the Sierra Madre Oriental records some very low temperatures during nortes. In Denmark, Picea engelmannii subsp. mexicana from the SMOri was undamaged by -27ðC in the record-breaking 1981-82 winter. Picea chihuahuana was damaged, but not killed, by the same.

Resin

Johnny, a few questions about the Abies vejarii. Are the needles fragrant? Does it seem to be tolerating summer heat well on its own, or was it a plant grafted onto A. firma? And where did you get it? (might answer question 2, as I believe only porterhowse ever offered rare species grafted onto A. firma)
BTW if you are really borderline 6b in the mountains of GA, though, I assume you are at least 2000' and your nights could be relatively cool. What is your elevation?

Here are the Rushford groupings again via Resin:
:

Group 1 bracteata.
Group 2 alba, cephalonica, nordmanniana, borisii-regis, bornmuelleriana, nebrodensis, equi-trojani.
Group 3 pinsapo, numidica, cilicica, tazaotana, marocana
Group 4 firma, homolepis, recurvata, pindrow, gamblei, chensiensis, holophylla, beshanzuensis [kawakamii].
Group 5 amabilis, mariesii.
Group 6 spectabilis, densa, delavayi, forrestii, fabri, fargesii, squamata, chengii.
Group 7 sibirica, semenovii, nephrolepis, sachalinensis, veitchii, koreana, sikokiana, [kawakamii - moved to group 4], lasiocarpa, balsamea, fraseri.
Group 8 grandis, concolor, durangensis, coahuilensis, mexicana, guatemalensis.
Group 9 procera, magnifica.
Group 10 religiosa, vejari, hickelii, oaxacana.

Hi David, I pulled off a few needles of A vejarii and A. balsamea this morning and gave them the "crush test", as expected the Balsam is more fragrant but at 32 F/0 C the odor was greatly subdued, suggesting a more representative test be carried out during hotter temps.
It's still to early in the game to evaluate heat tolerance in this on going experiment. I have 3-3 year grafts(Porterhowse clone) that are grafted on Abies firma and 2-1 year grafts("Mountain Blue" clone) on Abies bornmuelleriana.
I noticed Don Howse has/had "Mountain Blue" on his availability list but haven't contacted to check on the understock used. BTW.. I live at 1800' msl but have various conifer plantings ranging from 1200' to 5600' in elev. PS Send me a email

Johnny