Trees in grow boxes slowing down.

[kale]

Hello! Last summer, it seemed like several of my trees in grow boxes didnt grow as much as they did in prior years. They have been in their boxes for 2 years now. Is that an indication its time to do some root pruning? When I planted them originally, it seemed like they really took off that summer. They are all pretty young. The trunks range from 1-2” thick and are in boxes about 14” square by 4” deep.

 

[bonsaichile]

If you are not doing root work yearly on those young trees, it will be hard to develop a good nebari/root spread later on

 

[kale]

If you are not doing root work yearly on those young trees, it will be hard to develop a good nebari/root spread later on

Good to know! Thanks Andres! I’ll be doing that this spring then. Glad to hear, sounds fun to get my hands dirty on some roots again. Been a while.

 

[Matte91]

If you prune the roots = the growth will slow down
If you put a tree in a bigger container = the tree will grow more
When the roots has filled the container = the growth slow down

 

[Shibui]

When the roots fill the container = growth will slow down
Pruning roots will not necessarily slow growth. It may temporarily slow growth but growth will take off again soon as roots recover - usually just a few weeks. Pruning 1 root usually induces 2-4 new roots that are all feeding the tree. New space for roots = increased growth. Rejuvenated soil = more growth. I certainly get increased growth from most trees in the season after root pruning then it gradually slows as roots fill the container again.

Different species react different to root pruning.
Most deciduous recover easily and show increased growth after root pruning.
Pines and junipers recover more slowly so growth may be slowed for a season (or 2 depending on extent of root reduction) then recover after that.

Lack of nutrients is another major cause of slow growth. Make sure you keep up, and even increase, fertilizer in subsequent years to maintain growth rates.

 

[Bonsai Nut]

Hello! Last summer, it seemed like several of my trees in grow boxes didnt grow as much as they did in prior years. They have been in their boxes for 2 years now. Is that an indication its time to do some root pruning? When I planted them originally, it seemed like they really took off that summer. They are all pretty young. The trunks range from 1-2” thick and are in boxes about 14” square by 4” deep.

A lot depends on your soil mix. If you are using a mix with a lot of organic material, the soil will compact quickly and will not be good in a year... or less. There is a reason why farmers plow their fields every spring before they plant - it is to loosen the soil.

If you are using an inorganic mix, your time between needed repots (all other things equal) will get longer.