There are several instances in which I use a plastic bag to protect a fig bonsai.

1. For rooting cuttings
2. Stressed trees that need time to recover
3. Recently re-potted trees that have been struggling
4. To develop aerial roots on figs that require constant humidity for aerial

In this case this Ficus rumphii has had all its roots cut off and is basically a large cutting. It is place into the baggie, watered well and the bag is opened every few days to make sure that the soil is moist. Never let the pot sit in water or the plant or cutting will rot. Also keep the bag in bright light but never in direct sunlight.

Remove the bag once the plant is growing properly.

Ficus rumphii sealed in the bag after removing all of its roots

Now recovered and wtih enough roots to live outside the bag. Also showing new aerials have formed on the trunk

Bag is removed as the plant has new roots and can survive outside the bag