HOW TO SAVE AND RECOVER AN OVERWATERED PLANT
Depending upon how far gone your over-watered plant is will depend on the treatment given. As a rule of thumb - the worse the condition the more drastic the treatment.
The immediate course of action is simple, remove the plant from its pot (or carefully lift the plant from the ground so as not to cause any further root damage) and to place it onto a couple of thick newspapers. The papers will act as a superb 'water-wick' drawing water down through the root ball. In extreme cases you may need to replace the soaked newspaper with dry every couple of hours, but if you are luck enough to be doing this on a sunny day then the sodden paper you have just removed will probably be dry enough to be used again - should you require it - later. With small pot grown plants, try not to be tempted to squeeze the root ball like a sponge as this can further damage to the root ball.
Plants lose moisture through stomatal pores found on the underside of leaves and the more leaves the plant has then the greater the surface area - and stomatal pores - it has with which to loose precious water from. In nature, when a plant become distress due to intense heat and drought, one of the safely mechanisms it will use is to drop its leaves, and move into a period of enforced dormancy until more favourable conditions return. This is a good system for deciduous plants which are genetically capable of dropping leaves, but when evergreen plants employ the same system it is usually to late for them to recover as they have dried out to far within the core plant.
With our over-watered plants we can enforce the same procedure. On deciduous plants -where over-watering has been recognised early - no further action may be required although you can remove some of the older, lower leaves to be on the safe side. Should the plants condition be a little more extreme it can be pruned back by 1/3 of it original growth. Also, if the specimen has particularly large leaves you can consider cutting these leaves in half.
The last thing to do is move the plant to a cool, shaded room and spray the remaining foliage periodically with tepid water.
Once the plant is on the road to recovery - this will be recognised by the appearance of new fibrous roots - it can be potted on, or replanted, taking care not to reproduce the conditions that cause the initial problem. Be aware though that when taking such drastic measures as outlined above, it can take several years before the plant will make a full recovery and begins looking like the specimen it was before over-watering occurred. With inexpensive and readily available plants you may be better off throwing the poor thing away and trying to learn from the mistake so that it is not repeated.