I have recently bought and acer palmatum and a juniper squamata. They both have poor drainage because are potted in normal soil. I have my bonsai soil mix(pumice, lava and zeolit) and i want to repot them. Should i do that? Another question: If i repot the juniper, i know that i must keep a part of the old soil, but i want to remove all the soil and plant it in pure anorganic mix.
I will post pictures with the acer. I want to minimize it by air layering the long branches. If i don't repot it, can i air layer the branches? I don't want to cut them and throw away.
Please give me some advices.

I guess it's not the best time to repot them.
The Acer is beautiful, plenty of options and yes, I would air layer some branches if possible.

So i will leave them to grow in their actual pots until next february.
The problem is that they are outside and it rains a lot these days. The drainage is very poor and they remain very wet all the time.
I will do some air layerings, hope to obtain a few more trees. Acer palmatum is hard to find here and i don't want to throw the branches.
Thank you Clicio.

Considering you bought healthy plants that were grown in your climate in that substrate, it cannot be all that bad...

If you are worried, make a temp shelter for the trees in fall when rains hit. Or put them in a garage for a bit.

There are multiple opinions on barerootong junipers. The older they are the more problems you get bare rootong them.

A little trick: Put a couple of rocks under the plastic pot to get if off the ground. That will improve the drainage a little.

Most everywhere the repotting season is over. Exactly when it begins and ends depends on your location. Around here (Birmingham, Alabama) it starts in January usually and ends in March, although I have been brave in April. I was just in Rochester, NY, and they said they were still repotting in May.