Cedars still tend to be problematic for me, but I will share what I have learned. Jim Gremel has also had problems, especially lifting them from his field. We have come to different conclusions, but I really haven't tried his method.
After lots of experimentation, Jim has decided that the best time for HIM is in late spring after the new growth has extended. He says that sometimes they will even wilt, but then recover. We had this discussion about four years ago, so it may have changed. You also have to consider that Jim lives just a few miles from the ocean in Redwood country, so his climate is vastly different from mine at that time of the year. He has very mild conditions with fog, while my place is baking by then.
Most of the transplanting I have done after the new bud break has failed. I prefer to rootprune and transplant while they are still deeply dormant. For my zone 8, this after Christmas and the month of January and perhaps early February. Later than that, defoliation will occur. I have had completely defoliated trees recover, but it really sets them back. You must keep the root pruning to a minimum, always making sure that a good portion of the root ball is untouched, such as slicing off the bottom mass and loosening the outer roots, but not working your way into the rootball. Doing a total rootpruning and soil change should happen over several years. I have a monster C. atlantica that needs this badly and I have already missed the window for this year, so I will probably just slip pot it for this year and try again next year.
Some other points and observations: Most of the blue Atlas cedars that you come across are grafted to Deodar cedar (C. deodara). This makes things a bit easier because Deodar is nearly bullet proof, but still requires the above care when root pruning and repotting. You may get away with a bit more, but I wouldn't press my luck. When working with the other Cedrus species on their own roots, be extra careful. Planting cedars in the ground has led me to believe that part of the problem is soil temperature. Whe I put cedars in the field, it is usually late because that is when I get around to it. Last year, I planted 50 C. atlantica from small pots into my field of fairly heavy clay in April or May. These were very root bound and I just sliced off the outside and bottom roots with shears. I didn't have time to mess with them. Nearly all of them survived and are getting ready to bud out for this year. I have had the same success with grafted 'Glauca' blue atlas cedars in the landscape. All of them have suvived. In each case however, I have left a good portion of the rootball intact. Had I planted the little cedars in cans rather than in the field, I could have expected to lose a quarter to half of them. I think the moderating temperature of the field soil keeps them from being 'cooked' while they are rooting out. Warm soil is fine, but our temps are often in the high 90's F in late spring, so the soi in cans gets to this temp even in the shade. In the sun, it gets higher than the ambient temp, often over 100F.
I agree with all that's said about loose porous soil. Cedars will get root rot in the blink of an eye in pots with bad soil, and water must drain right through your mix. In the proper soil, cedars will completely root colonize the pots as if the root ball is a solid chunk of wood. In the wrong mix, the soil will collapse into muck and your tree will be in great danger.
I agree about Jim's cedars, they are to die for. I could kick myself now for not buying one after he first dug some about six or seven years ago. I didn't have the money and now they are three times as much, but still worth every penny. By the way, I believe Jim's blue Atlas cascade won the 'best of show' or whatever it's called at last year's US bonsai convention in NY.
Brent
EvergreenGardenworks.com
