I have bareroot bench gtafts that I am potting up. Some of the root systems are deep - they have long taproots, which is nice, until I try to get them into a pot. This is an issue primarily with a few Mahaleb and Manchurian rootstocks.
How much would it injure/harm the young tree if I pruned a few inches off of the taproot? What other options do I have?
This is a lanky Manchurian root system.
I would go for it, especially since it has those fine feeder roots. Those are the important part. Pruning the taproot back will encourage more fine roots to develop, just like pruning up top works. My Manchurian apricots looked similar. I used taller pots, but still nibbled a bit off the bottom and they are all growing vigorously.
Notice, the roots growing sharp angle are downwards, you can call them miniature taproots. I wouldn’t worry much.
My area, taproots are required for paw paw and persimmon, that’s the reason I prefer growing those from seedlings. A good rootball is just not enough. My soil here in Arkansas is drying out too fast.(Rocky).