Repotting & Root Pruning Trees
Re-potting a Bonsai tree is not hard and a lot of people worry about this stage of bonsai care. So long as you follow a few basic principles and understand what type of tree you have then things should be easy. When the roots of a tree fill up the bonsai pot after a few years you will need to re-pot the tree. With a normal plant you would simply find a bigger plant pot to put the tree in and fill in the gaps with soil. A bonsai tree is different because we often want to keep the same sized pot to keep the proportions and scale of the tree in balance. So to do this we prune the roots of the tree and are then able to put it back into the same pot giving the roots space to grow.
When we are root pruning we are taking all of the unwanted roots away and allowing the fine feeder roots space to grow. It is these fine feeder roots that will allow your tree to flourish. More often than not you will want to repot your trees in spring but certain species can be re-potted throughout the summer months.
When we re-pot our tree it is a good time to decide on the viewing angle and whether or not you wish to change the position the tree is placed in the pot. You would not want the front viewing angle of a tree visible from the short side of a rectangular pot. Sounds simple enough but we have seen plenty of trees that have been re-potted with little thought to the viewing angle.
Another nice thing about re-potting is that you can start to expose some of the top roots through the soil by lowering the soil level by a centimeter or 2, and gently scraping away the top layer of soil.
-Use your root hook to gently come out the roots and the soil. Do not damage the mature top roots. As you start to tease the roots out the long hanging roots will need to be cut until you end up with a tidy nice compact root ball.
-If you are re-potting the tree back into its original pot make sure you give the pot a good clean beforehand.
-Remember to place plastic mesh over the holes in the pot so that your new soil does not fall out when watering the tree.
-Water thoroughly after re-potting
You may wish to use a new pot for the tree or place the tree in a bigger pot if you feel the tree has outgrown its original container.
When we re-pot our tree it is a good time to decide on the viewing angle and whether or not you wish to change the position the tree is placed in the pot. You would not want the front viewing angle of a tree visible from the short side of a rectangular pot. Sounds simple enough but we have seen plenty of trees that have been re-potted with little thought to the viewing angle.
Another nice thing about re-potting is that you can start to expose some of the top roots through the soil by lowering the soil level by a centimeter or 2, and gently scraping away the top layer of soil.
-Use your root hook to gently come out the roots and the soil. Do not damage the mature top roots. As you start to tease the roots out the long hanging roots will need to be cut until you end up with a tidy nice compact root ball.
-If you are re-potting the tree back into its original pot make sure you give the pot a good clean beforehand.
-Remember to place plastic mesh over the holes in the pot so that your new soil does not fall out when watering the tree.
-Water thoroughly after re-potting
You may wish to use a new pot for the tree or place the tree in a bigger pot if you feel the tree has outgrown its original container.
Learn Your Tree Type
Most trees can be re-potted using a rake or root hook and teasing the roots out but certain species have very exacting standards like the Japanese White Pine. A White Pine will not tolerate having too much of it's roots cut and will die of shock if too much is removed
An Acer bonsai will happily have a lot of the root ball cut away after you have teased the soil and roots out with your root hook, but an Azalea will not. An Azalea bonsai tree does not like to have it's roots ripped which is what can happen when teasing roots out with a root hook. The advise generally given for Azalea is to cut a bottom section of the root ball with very sharp scissors. to avoid tearing of the roots. If you have an Azalea or a white pine then make sure you research how to re-pot it. There are tons of youtube videos out there that will show you how.