I have had a Ficus tree for 28 years and it was doing beautifully until we had some furnace repair and decided to get a heat pump in the room where the Ficus lived and removed the floor heating. We only turn the heat pump on when we are in that room. I didn’t think anything of it until the leaves fell off in droves. I moved the tree to a warmer room, pruned the dead branches. Now it is not soaking up any water. It just lays in the tray below. I am sad about this since I have had it so long. Any chance of recovery????
The degree of damage caused by cold depends on just how low the temperature got and how long it was exposed to the cold. So I cannot say whether or not it will recover.
I can tell you that the leaves are the most exposed and they fall off first. The roots, however, are more important long term and they are insulated from the cold somewhat by the pot and soil. Thus, it is possible for all the leaves to die, but if the roots survive, then new leaf growth will be produced when temps are kept warm.
I don’t recommend watering from the bottom. Top watering is much more effective and gives you better control.
Either your Ficus is already dead or its growth rate has slowed down substantially so either way it will not use much water. Therefore, you have to be careful not to inadvertently rot the roots. Allow the top inch of soil to dry before adding any water. Add just enough so that it reaches that level of dryness again in abut a week.
Try to keep your Ficus as warm as possible and provide maximum sunlight to help it recover. Do NOT fertilize it until it has fully recovered and is growing vigorously. Fertilizer is not medicine. Finally, any stems or branches that are dry and brittle are dead and can be pruned off.