I live by the ocean in So. California. I have a Gardenia "tree" in a large pot on my patio. This winter I thought it may have been poisoned. The leaves turn dark brown and wilt, though there is plenty of moisture in the soil. When I water or it rains, I move the pot and there is a little oil slick on the water that drained out of the pot. I do not add anything but distilled water or rain water and some fertilizer for new growth. It's dying. Help.
Gardenia Tree in Outdoor Pot
Certified GKH Gardening Expert
Wilting can be caused by overwatering as well as underwatering, so make sure the plant is not staying too soggy all the time but is drying out a bit between waterings. However, it is strange that there is oil coming out of the pot, and this could definitely be the root of its problems. Could it be something leaching out of the pot itself? Also, make sure you're not adding more than the recommended amount of fertilizer.
In any case, the best thing to do is to try to wash whatever it is out of the soil. To do this, don't increase watering frequency (since this could drown the plant's roots), but each time you water, water very well and let the water run freely out the drainage holes to rinse the soil. Or, you could repot the plant in new soil.