You can carefully move soil away from the sprout with no worry about significant or permanent harm. This should reveal whether or not the sprout is a basal sprout attached to a lower order root, or simply a volunteer that has somehow made its way into the pot. If, after you clear some of the soil away, you tug on the sprout, pay particular attention if that tug also causes a visibal root to move in concert with the sprout. This would lend some support to the idea it is attached to the roots.

Still, removing a basal sprout is relatively harmless to the organism as a whole. The only reasons you might want to allow it to continue growing are A) you can envision it contributing to to the composition .... or B) You would like to treat it as a propagule to start another plant.

Al

Hello!

Thank you very much for your reply.

I initially tried to remove it around 3 montsh ago but couldn´t fully take it all. It ended up growing again recently. I removed it again a couple of days ago. This time I dug more and I could remove the whole bulb that was a bit mingled with the roots of the bonsai. I don´t know how it ended up there but I have an additional bulb growing in a different pot. To be seen what it is. Hopefully, it didn´t damaged the bonsai much by digging.

Odds are extremely high you (the plant) will be fine. You can also kill unwanted volunteers if you remove any green growth as soon as it appears. This limits the plant's ability to make food via photosynthesis, which forces it to use its energy reserves to fuel new growth. Since the reserve energy source is finite, the plant will deplete it's reserves. No reserve energy + no ability to synthesize current photosynthate to maintain existing living mass = loss of viability.

Al

Thanks a lot Tapla, your comments guided me really well. I have one more question if I may take 5 minutes from your time.

I live in Brussels and I am planning on repotting this tree in the coming month.

I have been recommended the following soil:

https://ibuki-shop.com/shop/sieved-substrates/general-mixes/general-mixes-with-regular-akadama/mix-akadama-60-lava-40-ibuki-bonsai-sieved-substrate-for-leaf-trees-65-7mm/

But I don't understand if I should mix this with organic soil or just use this mix.

What do you think? Thanks!

Use as is.

This ^^^ is what I make myself and use as the basis for all my trees.

Al

Many thanks!

That is a nice bonsai soil and reasonable price too.

Hello!

I haven't received the new soil yet so it's still with the old one. It's not looking great lately.

Since the sprout came up the leaves started to look slightly scorched/dry. It's not looking any better since I removed the sprout.

I moved it recently under grow lights and try to keep the humidity up.

Any action you can recommend here?

Thanks!

Looks like it dried out a lot although the soil looks pretty moist to me. How do you water? It could as well be caused by over-watering. Is there a heating vent close by? Dry hot air from hot air vents can also cause the leaves to be stressed.

Thanks for your answer.

1. Temperature is stable in my living room, between 19°-20.5° C. It's not near a a window or a heating source.
2. Light is stable too now. It's has been under a grow light for the last 2 weeks on a 12 hours a day basis.
3. Humidity: I keep a humidity trail (don't know how useful this is) and mist it daily.

4. Watering: I'm watering every 3 days or so.

I am planning on moving it outside once the weather gets better but it's rather cold right now in Brussels.

Why such a large % of trees fare poorly indoors:

In nature, the respiration rate (the rate at which the plant uses food/ "burns" energy) must be lower than or at worst equal to the rate at which the plant makes its food/energy during photosynthesis if the plant is to remain viable. Outdoors, cool temperatures in autumn/winter/spring would slow respiration markedly, so the tree remains roughly in balance with the plant's reduced ability to create food/energy during shorter fall/winter days and lower light intensity.

When you bring trees or temperate plants indoors, the relatively high indoor temperatures and low humidity levels caused respiratory function to skyrocket, while simultaneously, low indoor light levels notably limited the plant's ability to create food/energy. So substantively, a large fraction of plants grown indoors are starved to death because the respiratory rate outstrips the plants ability to synthesize food.

Al

So increasing light with artificial grow light should help the plant fight the higher temperature and lower humidity levels putting her in a perennial summer. I guess this is not great either for it.