In early April I planted a few trees into giant pots, as an alternative to field growing as I don't have my own garden to dig up and experiment in. This is the result after the first year.
I have been putting wire around the trunks as a Dendrometer so that I could have a good idea of the growth. Next year when they are settled I will be more scientific in my observations and keep more regular measurements.
It seems that the strong growth of wood begins in early April and ends in early September - before and after that there is still a lot of vegetative growth. This is outdoors and will be different under glass - early budding maples in cold shelters will have their major expansion earlier in the year.
Next year I will be sure to regularly water and fertilise during this critical period of growth (March to May). On established bonsai this is the time to go easy on the feeding to avoid big leaves and fat shoots.
This is an early August picture of the base of the oak tree. There is some good expansion already.
This picture was taken in early December after the leaves had dropped. I used a match box for scale (which is 5.5cm wide). There seems to have been another bit of growth since the previous picture. This is no surprise as it had been very active above ground.
The beech expansion was less impressive but still good. Its already quite a lot bigger than the oak - I think its a year older.
Given the behaviour of the root systems it is my opinion the trees must be potted and settled by mid March.
On both of these trees (especially the oak) I have been constantly pruning to keep their apical dominance at bay. I am specifically encouraging the lower side branches on both.
So far it all seems to be working.