Hi, so this summer in august i bought my first bonsai tree, a ficus bonsai. The first couple of months there were no issues and the tree seemed healthy, however, as the season started to shift I noticed the bonsai was starting to drop some leaves. This started about two months ago. At first I though this might be due to the change in season however it has steadily kept dropping leaves up untill now. So I'm wondering what I'm doing wrong cause I'm not sure anymore. I've noticed some of the branches that drop leaves are very dry and the ends start to shrivel and some of the tips are black. Some of the leaves have a black end or are a bit yellow but more often a fully green leaf can also drop. I try to water when the top of the soil has become dry. In the summer this would usually be every couple of days. However in the winter, now, I've noticed the soils remains wet for a much longer period, sometimes up to a week. So I'm not sure if this is an overwatering or underwatering issue or too little light in the winter. Should I water when the soil is still a little moist ? (I've included some pictures, one is taken a coupple of days after being watered)

Any advice is appreciated .
Thanks in advance !

Nice tree you have there.

In general, for this species, think: Humid tropics. So ideal growing conditions:

- Lots of (sun)light
- Moderately warm
- Good moisture available
- Humid air

The first three need to be balanced. If there is little light and it is cool, the tree should be kept a little drier, and the tree will slow down and enter a slumbering state.

Probably, this is kept in the living room. Moderately warm. Watering might be dificult so roots are switching between dry and wet a lot. It is DARK in living rooms, especially in winter. And the air is dry. So you have an unbalanced growing situation and the plant is struggling. It is dropping leaves in areas that are darkest (Room-side and lower branches) and pushing a bit of growth in the top, hoping to grow out into the sun.

Putting it in a sunny spot in a cool room can help to pull this through into spring. Or explore whether your living room has a window facing the sun at noon, put it there. Or you can get a modest growlight (for 10-20 usd on amazon already; Look for one with white light; The purple lights are horrible to look at!).

Make sure you do not let the pot dry out completely, yet do not have the soil saturated. Tricky situation. And if it is in the soil you bought it in, it probably is some black muck that goes brick-hard. That stuff is impossible to regulate water in.

Last resort if you think it might be the roots / substrate would be to look for good quality potting soil (Cactus mix oddly enough often is very good with light gravel n there) or get granular bonsai substrate (The last I would not recommend, if you intent to keep this as a living room plant). Then lift from the pot, roughen the outside of the rootball till you have small roots poking out and drop the whole thing into a pot a few cm larger than you have now. In spring/summer once it is healthy, you can consider cleaning the rootball from the stuff it is in now,

Thank you for the response !

It is indeed in a living room like situation (bedroom/home office) with moderate temperatures 19-21 degrees. It faces the window on right side. The place that first started dropping leaves was the left side (room facing side) that is now completely bare so my first though was not enough light. I tried putting it on a windowsill at a window that faces the sun direcctly in the morning, but not at noon. I might try again moving it there and waiting for a longer period or look for a growing light.

It is also still in the soil that I bought it in. So the substrate was also something that I was considering but I'm not sure how to properly identify this. However I was also waiting for the spring untill it was healthy again before repotting. In case it keeps dropping leaves I might try putting it in a bigger pot with new substrate around it as you said, didn't know about that option .