"5-needled Pines. Again, Jorg Kohout suggests: Pinus armandii, Pinus wallichiana. Americans use exclusively strobus" - I'd carry on with P. strobus. The other two may well have cold-hardiness problems, anywhere colder than zone 7-8. "3-needled and combinations of 2-3-needled pines: A friend in the US has found Pinus ponderosa to be a very useful understock. Pinus strobus also seems to be a US choice" - yes to Pinus ponderosa; but not Pinus strobus, except for Pinus bungeana and pinyon pines (these are more closely related to white pines than to P. ponderosa, etc.). "Nootka grafted to Microbiota" - that's just weird, grafting a common plant (Nootka Cypress) on a rare rootstock (Microbiota) . . . I could understand the other way round! Resin

They look like they're perfectly rooted. I'd simply pot those to an 'Anderson tree band pot' that's taller than the root-system. Everyone who uses Anderson band pots uses the larger of the 5" size, however, your plug looks to already be 5" tall so, use the 9" tall band pot. I'll provide you a link. After your plants are fully-rooted & after grafting, just be sure to tease all the roots prior to planting. You'll want to inspect all roots that are container-grown, always. Dax Here is a link that might be useful: Grower's Nursery Supply, Inc.

in my experience Abies lasiocarpa is more sensitive to heat and humidity (born out by the paucity of arboretum and public garden specimens in the mid-Atlantic, versus A. concolor) so I'm not sure your improvement plan is actually going to help. If CK says Abies firma has been OK as a rootstock in zn 5, I'd be inclined to "trust but verify". Ask them if they know their customers didn't lose such plants in the recent polar vortex winters. But it sounds like you already discussed it with them.

That is true, UK overall a bit milder than PNW US, but I think there is something else going on. I think there's just more of a culture there (in UK) of identifying and trying out these candidate rare plants, than anywhere else. Maybe if someone botanized a bit more in northern India, they'd find a hardier Aesculus indica. But there are not as many people to do it with the PWN in mind. Our catching up process is always two steps forward, three steps back. Also the UK (and Europe to a broader extent) had and have, those networks formed around the Imperial and Commonwealth worlds as people moved back and forth. Even Ireland: a friend of our family was the daughter of a doctor attached to the Catholic mission in Nairobi. When they moved back to Dublin in the 1950s, she said they took as many seeds as they could find to see what would grow in their garden. She said an acacia tree lasted for years. (I'm going to guess though that it wasn't a native Kenyan species, but an A. dealbata planted by the Brits) Or take a kind elderly lady in New Zealand, who spent 30 minutes showing me her garden, told me her daughter had moved to the UK. So that sort of movement is still going on. Being, physically, in a place where a rare (to your home station) plant can be observed, is I'm sure an important part of the process. I tend to me more moved by things I see "IRL" than in pictures or videos. Though perhaps with me, watching Peter Seabrook's segments on Victory Garden got the fire started, and actually going to Europe and the UK in 1993 made it engulf my soul hahahaha. But in the final analysis, the cultures are just different, period. For example thank goodness we had a Mike Lee running Colvos for a while, but in a culture where the consumption of interesting plants is maybe appealing to only 2% of the PNW populace, instead of perhaps 8% of the overall UK populace, one get the impression the nursery never really took off financially...and he had to 'retire' back to doing landscaping. Because he was running it, I spotted a little known (to me and most people) Larix masterisiana in his last catalog, and got one. I don't think anyone else has quite filled the niche he occupied yet. Maybe the closest is Far Reaches; also I'm told via a third party that the guy who runs Keeping It Green (where I got my Meliosma tree) was just in India collecting. So, again, tiny steps...an optimist would say we are getting closer!