English Oak

Hi,
my oaks have very long tap roots and at their repotting earlier this year I didn’t trim them just left them and thinned the fine root growth.
should I trim the tap root in a similar manner as the others, removing a third for example. 
I grew them from acorns and would hate to damage them or worst case kill them.

Appreciate your advice on this.
Thanks 

I always remove the whole taproot at the very first time I see them. Removing fine feeder roots and leave the taproot seems like the total oppisite to normal bonsai practice.

Ah, I wondered as all the bonsai tips focus on thinning out the fine roots but never mention the taproot.
Thanks for the feedback and they’re going in the spring.

Maybe the reason for that is that you are searching information about bonsai care? At the point the tree is considered to be a bonsai it is 10 or more years since the taproot was removed.