Tasmanii, I had the impression that the Phyllocladus genus liked cool temperate climate. I tried one from New Zealand in Georgia (USA) (I forget the species name), and it melted in the hot and humid summer. When I saw Phyllocladus hypophyllus (from Brunei, Indonesia, Malaysia, Philippines, and Papua New Guinea), I thought, Well, maybe, hypophyllus could handle the summers. Another consideration, as you indicate, is cold-hardiness. I was thinking about trying hypophyllus in coastal Georgia (not zone 7b), where the winters are milder. At the coast, there are different zones warming up as one goes closer to the ocean. At landÂs end, the temperature in winter may stay above 32F for many winters and dip below only in the odd winter. How far does it dip in that odd winter? Maybe, to 30F. Maybe, to 29F for a short couple of hours. On islands farther inland from the open ocean, the dip may go to 28, to 27, and so forth, every 4 to 5 winters. So if a plant is cold-hardy to the above degree, IÂm back to the consideration whether the plant can handle the hot and humid summers (and whether it can handle, as salicaceae mentions, the pathogens that rage at the summer peak of heat and humidity). I always imagine that Tasmania is like coastal California  not too hot, not too cold, cool temperate with dry summers(?). The moderate temperatures allow all manner of plants to survive and even thrive. The dry summers seem to allow plants to stay on top of pathogens. In other words, plant heaven.

Personally (and maybe this is just me being a homer), I think you are in somewhat of a sweet spot for conifers, especially if your zone 7a has a bit of elevation. I think you will find there are many more conifers that you can grow than not. In addition to some of the species listed above, many spruce will thrive in zone 7, including Picea abies, Picea orientalis, and Picea omorika, each of which has many really exciting (i.e. not boring) cultivars. Some even have success with Picea pungens (although many of mine struggle). And if you look for firs grafted onto Abies firma, you'll probably find you can grow many fir species, too. The South gets a bad rap for being inhospitable to many conifers, but there is a big difference between the Piedmont areas of the south and the coastal plain.

Thank you for the input everyone, Peter thats great news to see the three large seeded species have the same number of chromosomes! makes sense really as you said; they are morphologically very similar trees and not too distantly related. Interesting that you bring up the graft compatibility too as I know that both Wollemia and Various Araucaria have been successfully grafted to Agathis, makes you wonder what possibilities there could be in hybrid breeding projects with these archaic conifers. Completely agree on the Hybrid picture you've posted, Angustifolia foliage with a bunya silhouette. We really are lucky that the southern hemisphere has stayed stable enough for relict population like these to survive virtually unchanged, considering the massive climate swings over the course of the last 100 million years not to mention the Asteroid (or comet) that wiped out a majority of life on Earth touching down not too far from the ranges of Araucana and Angustifolia. Clearly extremely tough, resilient trees worthy of a damn site more attention, especially seeing as with some carful selection they can produce prodigal amounts of food with nothing more than sunlight, rain and average un-fertillized soil.

I guess it was missed the first time? Grafting won't improve hardiness. It seems obvious, given available evidence, that Wollemia in 8a would eventually perish; the long-term hardiness standards for a tree, particularly a tree like that (cannot return from roots like Eucalyptus) have to be (or at least ought to be) different from other plants like shrubs or perennials. Most 8a places in the US, at least, have record lows near 0F, which would probably kill even a mature Wollemia. The ones we know of getting long-term established so far* are all in maritime zone 8b climates at the coldest. The one the Smithsonian tried in DC died after a couple winters of upper single digits. Not what is indicative of '8a' performance. * what will happen to the ones in the UK when they have another winter like 63 or 85? Probably the ones in coastal or SW zone 9 areas will survive, and many of the rest won't.