It is important to allow the tree to dry out between waterings. They do not like to be wet around the roots. One of my colleagues has had a tree on a window sill through the winter and has only watered once every 2-3 weeks. The reason for immersion would be to enable the compost to re- wet as peat reduced growing media can be difficult to re-hydrate once it gets past a certain moisture point. If you do need to immerse the pot make sure that the any excess water has completley drained and refrain from putting the pot into a saucer. I may be teaching my preverbial grandmother to suck eggs but the best way of checking moisture content in the pot is by weight, once the pot feels light that is the time to water. It is a good idea to put the plant outside when the weather is a bit milder. If we have a mild spell during March and April give the tree a holiday outside for a couple of hours during the day. We do see some bronzing in trees but the drooping in the main is due to either under or over-watering.