Reviving a dying bonsai tree can take days or even weeks, depending on the condition of the tree. To revive a bonsai tree, you need pruning shears, a light insecticide, a clean container, and access to soil and water.
Trim the dead portions
Examine your bonsai tree. Look at the branches to find any areas that are browning or wilted. Use your pruning shears to cut these sections off. Remove the bonsai tree from its container and look at the roots. If you see any dead or rotting roots, clip them off as well. Try not to cut any healthy roots.
Apply the insecticide
Check the area around your tree to see if it has been impacted by bugs or fungi. If this is the case, use your light insecticide spray to give the foliage a light coating.
Clean the container and let the tree soak
Remove your bonsai tree from its container. Clean out the container and add in a fresh mix of soil. Place the tree back inside of the container, and place it in your sink. Fill the sink with water. Wait several hours so the soil becomes saturated with water and no longer contains any air. Let the container drain and remove the tree from the sink.