Question
When should I trim the plant?  The shoots are now very long, but it is indoors for the winter and may be setting buds.

Answer
Lisa,

Pruning gardenias keeps plants shapely and in scale. Pruning should be done just after the plant finishes blooming. Pruning after October 1st decreases next year's blooms.

The following website has excellent information on growing gardenias.  http://edis.ifas.ufl.edu/BODY_MG336
Moving it to a sunnier location indoors might help reduce the growth of long shoots. If you have more questions after reading the above site feel free to write again. Good luck.

Darlene