Gardenias are probably one of my favorite of flowers . I keep mine outside for a large part of the year (March-Nov), then it goes into a sunny garge that is chilly but frost free in the WInter. Gardenias enjoy good ventilation so a plastic bag would not be ideal. I don't know what zone you're in but there is even a gardenia variety said to be cold hardy to zone 7 . Indoors they are much more challenging but would suggest that you can increase the local humidity by sitting them on a pebble tray with water in it. Don't worry about the bottom of the pot sitting in a bit of water, gardenias are one of the few plants that can actually benefit from this constant supply of water. Good lluck!

I do take mine outside in the summer bring it in for the winter. But it is inside more than outside because of my zone. I cannot put mine outside until late May-early June. It comes inside in Sept.

I keep it in a large aquarium because mine is large plant now but like you it was a impulse grocery store purchase. I also have one that was sent to me as a trade that was a small cutting that has grown into a very large plant. Both kept in the aquarium in the winter.

I found after several tries that the humidity was key to keeping them alive indoors.

njoasis suggestion is probably the best thing I can think of to keep that humidity high. It is the same concept I am using only mine is a little more confined because it is sitting in the aquarium. If you do not have a old aquarium sitting in a corner. I happened to have one that was not in use so it was a good alternative for me.

Also, I should have added, it really helps to keep the Winter temps on the lower side during the indoor/winter season.

Summer, my Gardenia was purchased 1994/5. It has its ups and downs, but continues growing.

I agree with Nj keeping your Gardenia in a plastic bag would be more harmful than helpful, however, it wouldn't hurt setting inside a plastic bag a few day w/the top opened. Especially if your 'dena has been kept in a green house environment.

Afterwards, place pot on a saucer w/stones/pebbles, and water, but water mustn't touch drainage holes.

During winter, my Gardenias are misted 2-3 times a day..

If possible, keep in a sunny, cool room, away from a heat source. Shower foliage once a week, sink/shower.

How tall is your Gardenia?

Over the years, I've purchased Gardenias in 4" pots..They died. However, standard types, at the minimum 1' in height are doing well. Not the best-looking, but thriving.

I believe everyone who live in cold climates should own a humidifer..lol..
Not only does humidity help our plants, but healthy for people, too. Who likes dry skin? I can't breathe when air is too dry.

When it's time to fertilize, use a fert for acidic plants. My Gardenias are fertilized with timed-release, Rhododendron/Azalea fertilizer.

They're not the easiest plants indoors, but with some work, your Gardenia should do fine. Toni

YES! :) I have a Frostproof gardenia that I keep indoor all year. In fact, all my plants are indoors all year round since I live in an apartment and I don't have a balcony. They live by my south-facing windows and on a good sunny day they would get ~3-5 hrs of sunlight. :) I find Frostproof to be an easy cultivar to grow.

Not just gardenia, I also have other fragrant plants: brunfelsia, aglaia odorata (my favorite!) and jasmines. I highly recommend an aglaia odorata for your home; it has one of the most pure flora scents that i've ever smelled.

Thanks for the reassurance. After reading about so many people having problems, it's nice to hear that it's not totally impossible.
My gardenia is one of the small ones because I would not have the confidence to spend the money on a large one. :) It has buds right now and so far they haven't fallen off (though I almost worry I'm jinxing it by saying that). It's in a room that tends to be cool in the winter and is a bit more humid than the rest of the house because I have aquariums in there (stocked with fish, not empty ones). It's not in the ideal amount of sunlight right now because my best sunny spots are already filled with plants and I quarantine all new arrivals. I am nervous about if the gardenia can tolerate the quarantine period, which is one reason that I was asking how fast they decline. I'm hoping that it can hang in there.