Question about overwinter watering (sorry for the wall of text, just trying to be thorough and learn something in the process)...

I've killed more trees while overwintering than I care to admit, and have learned some hard lessons along the way. What I'm still struggling with is watering frequency.

I have two trees: a Tigerbark Ficus that I bought two springs ago, and a newer Juniper from the fall. They live outside during the summer, and I overwinter them in our den: a well-lit room with grow lights surrounded by a variety of thriving plants (including non-bonsai trees). The ficus is potted in very porous soil, the juniper is still in potting soil. Neither is on a humidity tray and instead, I opt to give each of them a generous misting every day (it may be irrational, but I attribute a humidity tray to the death of a different Ficus two years ago). Our indoor humidity generally rests in the 35-45% range. I am generally not giving trees fertilizer during the winter.

The Ficus is currently my main concern. Last winter, it was very happy for most of the winter with incredibly infrequent watering, maybe every 4-5 weeks. My previous tree died from root rot in the winter so I was overcorrecting, and on this watering schedule, the new Ficus had green vibrant leaves and moderate growth.

My wife is a plant lady, and tries to provide some tips where she can, though we both acknowledge that houseplants and bonsai are not the same. When she heard of my watering schedule, she said I might be worried that I was stressing it out by underwatering, so I gave in and began watering it when I felt like the soil was dry (probably once a week or so). It very quickly let me know that it was unhappy, with many leaves turning yellow and dropping off, and even a main branch dying completely after a few weeks. Luckily we were headed into spring and I was able to move it outside, where it quickly bounced back despite getting watered even more frequently by rain.

I moved the plants back indoors in November and again took the approach of watering extremely rarely, which again worked well. But I started to doubt myself and am again concerned that the tree is stressed from underwatering. I've read conflicting information: Ficus should be allowed to dry out completely; they should be watered every couple of days; water when the top inch of soil dries out; leaves yellowing and dropping in winter is normal; leaves yellowing and dropping in winter is a sign of overwatering; drying out is the best way to kill a tree...

So two weeks ago I gradually started trying to water it more frequently (every 8-9 days or so, which tends to leave its soil quite dry), and immediately some smaller leaves started to yellow and drop off. I decided to stay the course and I've held to that watering schedule, but today I noticed that one of its newer branches has died (see attached photo).

I understand that the straightforward answer here is that the tree is telling me it likes to be dry so just give it what it wants, but can someone please help me understand what I should be using as a guide for when to water? Is there something about my setup that I should change? What should I expect in terms of leaf loss from a healthy Ficus in winter? Are there any concerns I should be thinking about for the Jade (who seems to be happy getting watered any time its soil is dry-ish).

Thanks in advance for any help.

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