Grey bonsai

[jc93]

Hello everyone!
I’ve recently starting seeing this developing grey at the root of my bonsai and it’s become very worrying! As you can see, all the branches are healthy! However I don’t know why there is this grey spot at the bottom of the tree??

For context, I water my bonsai once a week and have recently started to mist it with water. Additionally, my bonsai gets plenty of sun light as it sits next to the window.

I would appreciate any feedback!

 

[PA_Penjing]

Did it appear when you started misting it? It's most likely just fungus from being wet all the time. If your soil only needs to be watered once a week it sounds like it's extremely heavy. I see the discoloration in the photo but it's to far away so see any detail. I'd definitely get that tree outside in a shady location once the outdoor temperatures are near the indoor temps. Sunlight and moving air will do wonders. Chinese elm appreciate full sun but if you put it outside in a sunny spot right away it will be shocked and get sun burn, then lose all the leaves. It would need to be gradually pushed toward a sunny spot every few days or week.

 

[Deep Sea Diver]

My first impression is salts from dried liquid fertilizer.
cheers
DSD sends

 

[Tums]

My first impression is salts from dried liquid fertilizer.
cheers
DSD sends

Or even just salts from hard tap water?

 

[penumbra]

Yes, as above. Salt or calcium buildup.

 

[19Mateo83]

+1, looks like mineral buildup

 

[Shibui]

I'd say mineral deposits also. Most water has some dissolved minerals. Some water sources have more than others. Adding fertilizer adds even more minerals to the equation.
As the water evaporates the minerals are left behind as they cannot evaporate - usually on the roots, soil surface and the pot. If leaves are misted regularly deposits can appear on the leaves. It gets worse as the weather warms up and evaporation increases. Also worse when watering is just enough to dampen soil. Watering enough to flush the soil helps to wash minerals through the soil and out the bottom and reduces mineral build up on the surface. Try taking the pot to the sink when it requires watering and flush the soil whenever you water it.

Good news is the deposits may be unsightly but not usually harmful for the tree.

The tree appears to be reasonably healthy but the new growth is showing elongated growth typical of low light indoors. Even though the window site appears to have good light it's probably not really enough for optimum Chinese elm growth.

 

[Crazy Diamond]

Wellcome to crazy!!

Copyright by @sorce

 

[jc93]

Perfect! Thank you everyone for the feedback, I really appreciate it! I recently just started using liquid mineral fertiliser and it must of shocked the tree.
I’ll flush out the minerals next time my bonsai needs watering.

Thank you!