Why/when to cut roots in field growing trees?

[Walldepartment]

First off, what is the point of cutting the roots around field grown trees? Especially if they are growing on a tile. You are trying to thicken and develop the trunk as fast as possible, so this would slow its grow.

Second, assuming there is a good answer to the first question, how often should this be done or how do you know when it is a good time to do so?

 

[leatherback]

A few reasons come to mind.

You want to have evenly distributed roots, and not one run-away root. So cutting the roots every once in a while helps to avoid excessive run-away roots (For this purpose it is good to lift the tree and work the roots).

Secondly, you want to keep feeder roots near the trunk, so you can pot it up.


Finally, you are not looking for a few big roots, you want taper, side-roots, etcetc. Cutting roots helps.

It DOES slow down development. In general.. Cut roots: Year one, the tree sulks, rebuilding the roots. Second year, the tree benefits from being n the ground and starts to grow again. Year three is when you see real growth again. As such, 3-4 year interval would make sense.

 

[Walldepartment]

I’m wondering if it would be good to pull back the soil on the tile and selectively cut roots instead of doing all of it at once.

 

[leatherback]

I’m wondering if it would be good to pull back the soil on the tile and selectively cut roots instead of doing all of it at once.

I can see the reason why you want to. But.. Like trimming one branch on a tree often leads to poor backbudding responses compared to trimming all terminal branches, I think it would not result in what you hope for.

 

[Shibui]

Not all trees react the same. I now root prune trident maples every year and get amazing regrowth straight away. Slower growing species are don every 2-3 years.
Regular root pruning definitely improves nebari. Nebari is far more than just a few thick roots just as the canopy is far more than a few thick branches. Taper and ramification is just as important to the look of nebari as it is to the branches and trunk. Taper and ramification of roots is developed the same way as branches - pruning and selectively pruning and arranging the resulting mass of new smaller roots.

I’m wondering if it would be good to pull back the soil on the tile and selectively cut roots instead of doing all of it at once.

The problem with this is the underlying premise that root pruning is detrimental. If you can get your head around root pruning actually being no problem there's no reasons for doing things the hard way.
Selective root pruning depends on the species as well as the state of the roots. Selectively pruning strong roots should give the weaker ones some advantage and probably won't set back the strong ones enough to cause problems. Cutting weaker roots and leaving stronger ones untouched is likely to have a negative affect on the root structure
back to the original question.

First off, what is the point of cutting the roots around field grown trees? Especially if they are growing on a tile. You are trying to thicken and develop the trunk as fast as possible, so this would slow its grow.

I still contend that many species are not set back by root pruning. Take that or not but even if we assume growth will be reduced a bit, is it better to have a huge, fat ugly trunk quickly or would you rather have a better trunk with better nebari even if it did take a couple of years longer. I know that bigger is not always better. Quality over quantity any day for me.
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[Walldepartment]

Thanks guys. I understand now.