Coffee grounds and gardenia trees
Can you use fresh or used, not composted, coffee grounds on or with gardenia trees that have been moved inside for the winter or at all?
Certified GKH Gardening Expert
Coffee grounds can be used as a fertilizer in the soil of plants.
Winter however, is not the time to fertilize most plants. Your Gardenia is in it's dormancy and slower growing period and fertilizing should be done in the early spring and summer months.
Here are some articles with more information.