Sooner or later you'll need to repot your Bonsai, usually because its grown too many roots for the pot its in and the tree's health is suffering.
It's an easy thing to put off and I'm just as guilty as the next person and maybe more so since I truly know better. I lost a maple because it should have been repotted last year. I'm still not sure if my Japanese Black Pine (which I grew from seed) is going to forgive me for doing this year what I should have done two years ago. I'll know in the spring.
If you have bought a bonsai from me, with a few exceptions your tree should be fine for about two years, but since the trees I sell are young by bonsai standards, you'll probably need to repot the in second spring after you have them.
How can you tell?
The most obvious way to tell if your tree needs a new pot is to watch what happens when you water it. If the water immediately sinks into the soil a repot might not be in your immediate future, but if its been a few years it's still a good idea.
Most often, when your tree needs a repot you can tell because the water sinks into the soil very slowly. At the same time its a good bet that you've also noticed the tree doesn't look all that great and if its root bound, that will start to explain it.
If you see roots poking out of the drainage holes in the bottom of the pot, that's another pretty good indicator that they are over crowded.
You have a choice here as to whether to put the tree back in the same pot or move it to a larger one and that depends on what you want the tree to do!
If you want your tree to get bigger than move it to a pot that's one size larger.
If you remove your tree from the pot, visualize removing up to 1/3 of the root mass and it still looks like it won't fit in the current pot then go up a size.
If you want your tree to stay the same size, you can remove it from the pot, trim the roots and replace it in the same pot with new soil.
If you bought your bonsai as a small it's likely in a 6" pot, mediums are in 7" pots, large in 8" (*) and XL in 10". (*8" pots with saucers attached are deeper than 8" pots where the saucer is not attached.
I prefer to repot tropicals in the spring or early summer so that they are better able to grow and re-establish themselves in a new pot.
I don't really promote them on the site, but we do sell bonsai pots.
Here are main stages of a bonsai repot
- Evaluate - Does it need a pot?
- Decide if you want a bigger pot or will reuse the one it's already in.
- Remove the tree - First, If you see criss crossed wires on the underside cut them close to the holes. Carefully remove the top layer(s) of soil to uncover the rest of the wire and remove it carefully. Next, tease the soil away from the top and side of the pot so you're not ripping or breaking roots when you remove the tree. Keep working the soil and the wires until the tree comes easily out of the pot.
- Tease out the roots. I prefer to work on roots the day after a really good watering.The goal is to separate the roots from the soil and each other. Unwind the roots that might be wound around the top of the bottom of the pot. Be careful! Some trees have tough roots and others have roots that are so fine they are almost like thread while others can be very brittle and easy to break. A great tool to use is a wooden chopstick which does a wonderful job and unlike a metal root comb is gentle. For the record - Don't bareroot your tree. Don't hose down the roots to remove all the old soil ( but doe work with a mister on hand because you don't want the roots to dry out.
- Trim the Roots. Make sure you can recognize the feeder roots. Take a thick root with just a few feeders before you remove a smaller root with lots of feeders. Do not take more than 1/3 of the roots. Compare the new root ball with the new pot. Do they fit well?
- Replace the tree. Ideally put a layer of gravel along the bottom to allow for Oxygen in the pot. Add soil to accommodate the bottom of the root ball. Be sure to have replacement wire in the pot to help hold the tree steady. Place the tree as needed. Wire it down.
- Add the replacement soil a little at a time using the chopstick to help the soil find it's way into the space between the roots. You want each root to contact soil- not just other roots.
- Add a layer of gravel to the pot and then water until it runs out the bottom of the pot ( BUT, NOT IF YOU'RE REPOTTING A JADE.They get at least two weeks to allow the broken roots to scar over.)
These instructions are very general, don't hesitate to ask if you have questions specific to your own tree.