I noticed a comment on one of my species care guide posts and it said something along the lines of, ‘how do you actually repot a bonsai tree?’. I remember the first time I ever repotted my bonsai being stressful and really having no idea what I was doing, so I’ve put together a simple step by step guide to repotting a bonsai tree!
Whilst confined to a small pot it’s very important that the roots of a bonsai tree stay strong and active in order to keep the tree alive. We ensure this happens by repotting a bonsai tree every few years and pruning about a third of the roots, leading to regeneration of the roots and the bonsai tree getting stronger. Keep reading to following along this step by step guide to repotting your bonsai…
When To Repot A Bonsai Tree?
Different bonsai trees need to be repotted at different times depending on a lot of different factors including age and species. Young untrained trees should be repotted about every 2 years and this will decrease as the tree ages year on year. There are two main arguments for when to actually repot as it can be dangerous for the tree.
Repotting in autumn is the approach most bonsai owners and gardeners like to take. This can be effective but also poses a risk to the tree if you are not as experienced. After repotting, the roots need to regenerate and if you have repotted in autumn, these damaged roots won’t be able to repair for a long time as they need to survive the winter first. If you do repot in autumn, keeping the tree out of any frost snaps and barely watering is the best port of call.
Some bonsai owners repot during early spring as the roots are going to be very active in regeneration and repairing themselves, being much safer for the tree. The best thing to do is closely observe the tree and you should know when the time is going to be right for that specific tree, although this takes experience to be able to do.
1. The first step is to slowly and carefully get the tree out of the bonsai pot. Hold the trunk firmly near the base and start slowly working it out – you may need to use a stick to push up from the drainage holes if you’re having trouble. Remember not to be too forceful, you can cut round the edge of the pot if you’re really having trouble getting the tree out.
2. Once the tree is out of its pot, use a hook or chop sticks to start combing the roots, untangling them from the edges first. Whilst doing this a lot of soil is going to fall away, don’t worry as this is something we want anyway. Be sure not to rip the roots, just untangling them and spreading them out for now.
3. Keep untangling and spreading out the roots until you can see the base of the tree trunk. At this stage you’ll need to give the tree a gentle shake whilst holding the trunk to remove some of the soil still hanging on.
4. Now you’ll need to spray the roots with some water, don’t use too powerful of a hose but just enough force to give the roots moisture and continue to remove more soil. The purpose of removing the old soil is to get the new, healthier soil right next to the trees trunk whilst also removing anything that could possibly lead to infection.
5. Using a pair of clean pruning scissors, start pruning the larger roots that would have been touching the edge of the previous bonsai pot. Trim these roots back about 1/3 of their size, don’t worry about the small roots that will get cut away during the process, they will be growing back stronger.
6. Holding the base of the trunk, let the untangled roots dangle freely from the tree. You want to trim these roots to fit easily in the new pot with 1 cm around the edges to spare. To avoid this being stressful for the tree, aim to only trim about 1/3 of the total fine root mass.
7. Either prepare your new bonsai pot with mesh over the drainage holes, or clean out the original pot with soap before added new mesh. Prepare the wire going through the drainage holes as this is going to be needed to hold the tree firmly in the pot once planted.
8. Put some of your bonsai soil mix into the pot, with a small bump where the trunk will be positioned. You want to ensure that this soil comes to a level where the base of the trunk isn’t sitting above the actual lip of the bonsai pot.
9. Place your bonsai tree into the pot. Slowly push it into the soil and twist gently to get it stable. Once in and you’re happy with the position in the pot, using the wires you placed earlier, wrap them lightly around the roots to stabilize the tree for the first few months.
10. Add more bonsai soil into the pot, using your chop sticks to work it in to filling up the gaps in and around the roots. You’ll need to fill the soil up to about the rim of the bonsai pot, just below is perfect.
11. Once the soil has been sufficiently worked in with the chop sticks, give the tree a thorough watering before placing it in partial shade. Avoid full sun and feeding for the next month.