I bought a Serissa foetida a couple days ago from a nursery. Despite its being moved home in a cold climate, it seems to have coped well with the initial shock, so far. A few leaves have turned yellow (with dark green tips) and then fallen both today and yesterday. It looks quite healthy, however - by my amateur opinion. What concerns me is the base of the trunk. When I bought it, I noticed the trunk was greenish and a bit soft/flaky. Concerned, I asked the shop owner what this was - she said it was just moss, and that it would come right off and I shouldn't worry. On further inspection, it would seem this moss has grown under the bark of the tree at the base. Root structures have grown through the moss (removed in the picture), and these roots seem to belong to the tree itself. I would very much appreciate your advice. Is this a threat to the health of the tree? What should I do to help the tree? I don't want to shock the exposed roots coming off the trunk. Is this tree more prone to infection, having part of the bark gone?
Oh, more information relevant to the yellowing leaves. I already mentioned it is a cold climate here. I am using a humidity tray to regulate the humidity to 50-60%. I keep it by a west-facing windowsill at day with a 60W grow bulb, and close the very well insulated blinds at night. The temperature shouldn't drop below... say 60 F. Daily temperature ranges from 60-70 F. My watering schedule is 2x a week, tops - however, only if the soil is near dry. I feed every other week. It gets a full day of winter sunlight, supplemented with a grow bulb, from noon till bedtime (often quite late for me). I have not pruned at all or repotted - it is still in its plastic dish and the store's bonsai soil. Oh, and those serissa flowers are starting to develop. Looking forward to that, unless my tree decides to throw a climatic fit. Anyway, I greatly appreciate your time and help, thanks.