Hmmm... I'm a little confused why you used any orchid soil.

A good soil for a Gardenia is a composty, good quality acid mix. It is important for any plant to be given a good, thorough watering after potting, as this settles the soil around the roots and removes air pockets. So, regardless of how wet the roots are, or how much rain is expected, or how much it is currently pelting down, it is important to water in a freshly-potted or planted plant.

I don't know why the l;eaves fell off or why things are going black. I am no plant doctor, but things don't sound good.

Gardenia's love humidity. And good light. My guess is that it is pining for its spot in the garden. It sounds like it was doing very nicely there.

Are you sure it would be too cold for it there? How protected a place is it? Spots in the garden can be diffcult for us to know just how they feel, and it is the plants that can tell us this. Perhaps you could put the Gardenia back and see it it starts to pick up. It isn't at all happy where it currently lives.

When it got down the the 20s the first time several weeks ago, it ended up with black, frost-bit tips on the leaves. 40 degrees or colder and it just kinda flops over. My patio isn't the best spot for it, because it faces west (this is an apartment, so I don't have much choice), and if we have another very cold winter like last year it won't last. I was concerned that if I left it outside most of the time but brought it in when temperatures dropped below the zone 7 minimum, the shock of going from freezing to room temperature and then back out to freezing would do it more harm than just leaving it inside all winter. Should I not be worried about that? My other concern is that when it's outside, the squirrels dig around in the pot. I've put hot pepper flakes in there, which works for about a day before they're back to digging.

I used orchid soil because it seemed like it would do a better job draining in the absence of any gritty mix, which I can't find. I figured a mix of that and potting soil would be better than potting soil alone. It's only been a day, but there is no change. One half is still slowly dying back, the other half is just sitting there. At least now that it's in a smaller pot it's much easier to carry around, so I can move it back and forth between the kitchen table and the front window.

I don't wanna kill it with kindness, but I don't want to kill it with neglect either. I had an ixora bush last year that I planted by my sidewalk and buried with mulch for winter, but it died after the first hard freeze. I was trying to not have a repeat of that.

Here, I got a picture of it. I dunno if a picture will help though...

I see why you brought it inside. It would not have liked the cold patio.

My imagination can run rampant and I was imagining an acre of lushious garden with many warm pockets, and since it is nearly summer here, I have sort of almost forgotten the cold. Plus we have had the most beautiful rain so I feel positive about the garden.

You've done the right thing by not leaving your Gardenia outside.

Stick with the soil mix that you have and see how it goes. But I do think that it should be watered well, allowed to drain, then not watered again until the pot starts to feel a little light. It can be hard to gauge how much moisture a potted plant holds unless you lift it.

A little mist spray over the leaves will help to keep your plant happy.

The ingredients for a gritty mix are not written in stone. If you are having difficulty finding the recommended materials you can experiment.

Things like chicken grit can be found at most feed stores.

Aquarium gravel can be used (though the colors of most are quite garish) and you might be able to score some for free or cheap on Freecycle, Craigslist, Goodwill (or other thrift stores), or from a friend/relative.

You can use the puffed clay aggrevates like Hydroton/Primagra which is commonly sold at hydroponic stores.

Nurseries MIGHT carry medium grade perlite (though get the stuff without fertilizer added).

If you don't mind ordering stuff online, you can check out places like the one linked below for supplies that could work. (Btw, the site below does not have a shopping cart. Instead you call or email your order in. The older couple who own the business are good folks.)

Here is a link that might be useful: Roberts Flower Supply