Autumn repotting of very northern trees?

[EdwardH]

I remember reading Debora Koreshoff's book where she did experiments on root growth and stated that roots started growing at 18C though I don't remember which trees she was experimenting with. Like all living things, most tree species thrive under a variety of conditions and it would be hard to give a definitive answer of X degrees required for root growth.
I'm inclined to think that in a very cold climates, where the soil gets very cold or even freezes over winter, trees put out spring growth using nutrients stored over the winter/dormant period. Once the ground warms up, the roots start to grow. My guess it that this happens in late spring/early summer and that root growth would continue into mid Autumn or later - until the soil starts to freeze.
Using the above as my starting point, I guess that Autumn would be a good time to repot pines from colder climates.

[dansai]

I was told along time ago that trees either are growing leaves or roots. So if trees don't look actively growing then they are probably growing roots. I don't know how true this is.

Something we were taught at TAFE was that there was new (I did TAFE 5 years ago and it probably wasn't new) ideas on planting large advanced nursery trees. It had been common practice to remove up to 50% of the foliage to reduce the stress on the tree. It was found through scientific research (sorry I don't have a reference) that what this does is push the tree into foliage growth to replace what has been cut off. This may look better to the client, but puts added stress on the root system. Where as the tree that has no foliage removed may sit still for 6 months or more but in that time will establish its roots and grow much better when it does start to put on foliage.

So it makes sense that pines would concentrate on foliage in spring and roots in Autumn. It would also make sense as to why it's often said that you should root prune or top prune a pine but not both at the same time. I know some people do and report success, but it could confuse the tree into knowing wether to grow roots or foliage.

An often suggested best time for Natives is in the warmer months when they are resting between growth spurts. This would tie in to roots growing when foliage isn't.

[Grant Bowie]

Good point about not trimming foliage. You must leave the foliage full whether it is a conifer, native or even deciduous if you repot in early autumn.

And certainly trimming of roots in spring can retard the growth of the tree a little which is of benefit in warmer climes but less advantageous in cooler but not true cold climate. True cold climate you have little choice other than spring but you get a strong but late swing from winter to spring, and you would repot later in the calendar year.

Grant.