|new growth is infested with tiny black bugs ,(mites) HOW TO GET RID OF THEM
|Based on your description I am not certain if you are actually seeing spider mites (small, cause stippling on the foliage and also form fine webbing along stems and the undersides of foliage) or possibly aphids (smallbut easily visible soft bodied sucking insects which tend to congregate on the tender growth tips.) In either case, you can try to knock them off with a weekly spray of tepid water. They can both be treated with commercially formulated insecticidal soap as well, read and carefully follow the label directions. Spider mites thrive in warm dry air, so make sure the plant is being kept at a cool room temperature and if possible, raise the humidity level -- this would be better for the plant overall in any case. Aphids tend to attack plants that have been overfertilized, so keep that in mind. You would not be fertilizing a gardenia in the winter months, only in spring through fall. I hope this helps.