Discolouration and drying of my Chinese elm bonsai leaves

[Mirang19]

I got a Chinese elm bonsai as a surprise present around two weeks ago, but I'm having some difficulties with it. As soon as I got it I read into several care guides. I stuck a toothpick in the soil and only water it when the toothpick is dry and mist it once every 3/4 days. However, the bonsai seems to have powdery mildew on the surface of the soil. A week ago I watered it with 1 part milk and 5 parts water and the mildew took 6 days to reappear but definitely less worse than before so I guess it's working. But now some of the leaves turn this weird brown color around the edges. They feel dry to the touch, curl up after a few days and fall off.

The sun is not very bright, but I still only mist the tree in the very early mornings.

Should I water it more or less (with or without milk)? Is it the mildew causing this? Or should I stop misting the leaves even though they appear to be quite dry and discoloured?

Also I noticed quite some dead leaves and twigs in the soil. Is this helping the mildew thrive, should I repot the bonsai?

Lots of questions and lots of obliviousness, I know, but could someone please take the time to help me through this :'(

Kind regards,

Mirang

[Gnome]

Mirang,

Hello and welcome. I never mist Chinese Elms (outdoors) as they are subject to a fungal disease called black spot fungus. The damage to your leaves, however, does not look like this malady. Could you please post a picture of the soil? Is there any moss or pebbles present?

Instead of the toothpick try something a little more substantial such as a kitchen skewer. When I use this technique I prefer to leave the skewer in place removing it only to check the dampness. Try this, and I suspect you will water a little less often.

Give the tree the best light you can manage, a southern exposure in the northern hemisphere. Supplemental lighting will also make a difference. Fluorescent is preferable to conventional incandescent.

Norm

[Mirang19]

Hi Norm,

Thank you for welcoming me and for taking the time to respond.
There are no pebbles or moss present in the soil, here are two pictures:

With flash

Without flash

Like I said before there seem to be quite some dead leaves and twigs in the soil.

I was cautious with watering when I discovered the mildew, but I followed up on your advice and stuck a kitchen skewer into the soil and left it there overnight. In the morning I discovered it was quite dry and the younger leaves were hanging so I watered the bonsai (again with 1 to 5 mix of milk and water).

The bonsai is already standing in front of a window with southeastern exposure. I will follow up with your advice of fupplemental fluorescent lighting.

Again thank you,
Mirang

[Gnome]

Mirang,

I don't like the nature of the soil at all, it is very dense, perhaps even field soil. This type of soil is difficult to wet properly and, conversely, slow to dry. Both properties make your job harder.

If your soil is dry at the core you are not watering thoroughly. Every time you water your goal should be to saturate the entire root-ball. Proper watering is not about the quantity of water but the frequency at which it is applied.

As an emergency measure submerge the pot to its rim in a basin of water for 10-15 min to ensure that the soil is saturated. This is not recommended as a normal practice as there are advantages to top watering and disadvantages to bottom watering but on occasion it can be helpful.

Norm