I think I overwatered my gardenia. The soil tested okay, but half the leaves are now yellow. Should I cut off those leaves or transplant it to another pot? Due to cool weather, the soil is not drying out it seems, and I don't want to lose it. There are also a lot of flower buds, and I don't want to lose them either at this point. I have had the plant two years and it is finally going to bloom. What should I do?
The following article should be of some help to you:
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/helping-a-gardenia-bush-with-yellow-leaves.htm
Your article explains aphids and their residue that results in sooty mold very well, but didn't tell how to be rid of the pesty things. My gardenias are almost black with the stuff.
Neem oil has been known to be quite effective for treating both sooty mold and the aphids that can cause this fungus. Here is more info: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
When is the best time of the year to prune our outdoor gardenia shrubs?
The best time to prune is after the flowers have faded. Here is more information:
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/when-to-prune-a-gardenia.htm
I have a Gardenia bush and would like to know if you can cut back the limbs in the spring?
Wait until after it blooms to prune it. For now, it will just enjoy a bit of fertilizer. Here is some information that will help you:
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/when-to-prune-a-gardenia.htm
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/gardenia-plant.htm
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/fertilizing-gardenias-in-your-garden.htm
My bushes have a dark color to them, like maybe a fungus or something. I live in Conway, SC near Myrtle Beach.
It is sooty mold. It is an indicator of a pest problem. We recommend treating the plant with neem oil. These articles will help:
https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
Is it better to plant a gardenia bush in a pot or in the ground? I am a Florida snowbird so I will not be here year round. I am located on the Gulf side in Pinellas County.
It should be fine planted in the ground where you are. Planting it in the ground will help it survive while you are not there as well as it will not be dependent on your for water as it would if you had it in a container.
My Gardenias suffered some frost/cold weather damage this winter and are looking brown. Should I prune them back at this time, or will they come back on their own?
Wait until spring is fully here to cut back the plant. It will help protect the new growth, just in case another freeze occurs. Be aware that the buds will have been damaged and it is unlikely you will get flowers this year. These articles will help you as well:
https://www.gardeningknowhow.com/plant-problems/environmental/how-to-tell-if-a-plant-is-dead-and-how-to-recover-an-almost-dead-plant.htm
https://www.gardeningknowhow.com/plant-problems/environmental/tips-for-saving-cold-damaged-plants.htm
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/when-to-prune-a-gardenia.htm