Avi - Root congestion and problem roots hiding in the center of the root mass are greedy robbers of your plant's genetic potential. The point in time when the root/soil mass can be lifted from the pot intact is about when root congestion starts to take a toll, and it gets progressively worse with time. Unfortunately, trimming an inch or so off the outside of the root mass and filling the void surrounding the roots with fresh soil does little to alleviate the long term limitations imposed by congestion. In fact, it ensures that root congestion remains as a significant limiting factor for as long as it takes to get an actual pair of hands into the middle of the root mass to correct the congestion and other root problems. Sure, you'll see what most would consider to be a growth spurt after you pot up. In reality, it's not a growth spurt at all; rather it's a temporary return to growth a little closer to normal. IOW, absent root congestion, the plant would have been growing much better even than it did/does after potting up.
If I say root congestion can and does eventually rob your plant of more than 100% of it's growth potential, all but the most open minded would condemn me as nutts. Let me explain. From the 'liner' stage, nursery and greenhouse ops try to bump plants up a pot size before root congestion makes the root mass cohesive, which is essentially the stage where the root/soil mass can be lifted from the pot intact. Root congestion limits growth, often to the degree any growth that's occurring cannot be seen over the course of a year. Plants are shedding organisms. When it has parts/organs the root system is unable to service with water/nutrients, it sheds them. Growth, is not a measure of the increase in the dry weight of the plant. So, when a plant is extending a trunk or branch, in reality it isn't necessarily growing. In fact, if it's robbing mobile nutrients from its other organs, then shedding those organs in order that branch extension can occur, the plant could easily be losing o/a mass. We know with certainty that tight roots cause an easily identified syndrome referred to as the pompon or poodle look, where all the inner leaves have been shed and the few leaves remaining on the plant are clustered at only branch apices (ends) in small tufts. All of these trees are almost certainly sacrificing more than 100% of their growth potential to root congestion.
Here's what a repot looks like, and I've done thousands of them
Plant tissues retain their ontogenetic age, so the most vigorous tissues will be located in the transitional root to shoot zone. Whenever you cut back closer to this tissue, it has a remarkable rejuvenating effect, probably because the plant is being cut back to
JUVENILE tissues, thus the name re
juvenational pruning.
Plants regularly repotted will grow and develop 5-10x faster than those left to languish under potbound conditions or those only potted up, and they will maintain a much higher state of vitality while doing so.
Al
