Oh no. I just read this:

"Nematodes: Various nematodes (microscopic roundworms) feed on the roots of gardenias. Above-ground symptoms of root damage resulting from nematode feeding include wilting during hot, dry weather, oftentimes with recovery at night. Leaves may show yellow mottling and other indications of a nutritional deficiency. Over time the plant may become stunted and exhibit dieback of branches."

--that's exactly what happened to my plant slowly over the summer.

Further, "Below-ground symptoms depend on which nematode species are feeding as well as how many are feeding. Root damage can include stunting, discoloration, excessive branching and/or the presence of galls (small swellings of plant tissue). "

http://www.clemson.edu/extension/hgic/pests/plant_pests/shrubs/hgic2058.html

There's a picture there of the knobby, fleshy roots that looks a little like my plant.

Here is a link that might be useful: http://www.clemson.edu/extension/hgic/pests/plant_pests/shrubs/hgic2058.html

This post was edited by peterk312 on Fri, Aug 30, 13 at 12:08

I should have added that there's been no sign of new leaves or branch buds. I just assumed the plant basically went dormant trying to survive without having adequate roots. So, I made sure it was in the shade and have been waiting for a month now.

Peterk,
Put the plant back in the pot and go buy a moisture meter at your local store. They are cheap and easily available.
I am going to assume this is a new plant for you.
I am going to assume you live in a colder zone, below 7, and you wan tto keep it in pot for winter time.
Gardenias like morning sun. Afternoon shade.
They are like Rhododendrums, they are big shrubs, and they don't like being moved or depotted at all.
My best advise to you would be to leave it alone and water it with the hose once a week.
Put it in a basement that is cool in the winter, it hate being in a house over the winter, it hates it inside, and it hates dry heat.
Good luck. Don't fertilize it, leave it alone.
It's really going to get yellow leaves now, because you took out of the pot.
Yellow leaves falling off is OK. It's not dying, just complaining.
Brown leaves from the bottom up is bad.

Thanks for that bit of advice, but...

I only need the answer to my question. There's lots of info about growing gardenias on the Internet, along with lots of myths and superstitions (e.g., don't take it out of its pot! Now it will loose all its leaves!). My plant barely has any leaves and has had wilted branches and leaves in many places, which according to some people is grounds to toss it. It has green on the main trunk and some stems, but it's a tough call if you don't know what the roots should look like. Plus, I just found out that gardenias are real susceptible to root nematodes (see above link), and if that's the case, and it's difficult to know what to look for at the roots, then for all anyone knows nematodes might be why this plant does so poorly with so many people. I do not know, however, if plants in pots are as susceptible as plants in the ground.

I can't find much information on the Internet about what the roots of this plant should look like when they are healthy.

This post was edited by peterk312 on Fri, Aug 30, 13 at 12:55

Peterk,
Your roots are healthy.
Nemotodes live in the soil, in poor sandy soil in SC and south.
They are really bad in Florida, so I don't know where you live, but if you h ad it in the ground in Florida, there is a slight chance you might get nematode damage.
You don't have it now.
If you keep it in the pot, you won't get it.
Good Luck.
I was just trying to help, I have Many gardenias over ten years and was just trying to help from my experience.

Thank you again for the advice, butterfly4u. And the plant is back in its pot.

Because I bought this from Lowes when it was 50% off, I have no clue what they did with it or if it had been in the ground at the nursery and then potted up before it was shipped. Who knows what kind of contamination was possible. The plant was so sad looking with yellow leaves when I bought it. It's sort of been declining since then. I'm looking for signs that it is improving, and the condition of the roots has always been a concern to me. But since I don't know what might indicate a problem with the roots, that's why I'm looking for help.