We need more information.

How big are the plants and the pots? Are the plants rootbound?

IMO, it's not a good practice to plant warm season grasses this late in the year. Their dormancy period is right around the corner, and if the new plantings don't get their roots established before that happens, they may not survive the winter.

That said, you own them, and have to deal with them. The first thing I'd do is check them to see how rootbound they are. If they aren't overly cramped in the pots, I'd consider just burying the pots in the garden, completely, and in a protected location. Make sure they get enough water until dormancy sets in, and cross your fingers.

If they are rootbound, I'd pot them up to larger pots, after teasing the roots apart a good deal. Use black nursery pots, and position them where they'll get good sun and little wind for several weeks. Then bury them in the protected spot.

Late next spring, when soil temperatures have reached at least the 60's you can safely plant them in the ground.

BTW...how big is this bush you are replacing with 8 Zebra Grasses? They're going to want to be spaced at least 4' apart, and that covers a whole lot of area.

The bush is actually a big rounded type hedge that is 15 feet tall and 15 feet wide.

I have seen Zebra grass planted at our nearby mall CO-OP City,Bronx.NY and they are not planted that far apart and they look so nice. They look like one giant plant from a distance. Then when you look close at the bottom you notice that is several plants planted together. That's why I bought 8.

What I will do is set up them and look at how close they are noting what the width growth will be in a couple of years before I actually plant them. If it is too many, I will use the excess plants else where.

The plants are about 3 feet tall and all instructions said now in August and September is the best time to plant any ornamental grass.

Since they are from Home Depot, you know that they are probably a little root bound, so I will probably go out today and plant them in the dirt until I have the root removed, which should be in a couple of days. I will then transplant them to their final area.

I already had a zebra plant seem to die on me that I recently bought, I cut it back and replanted it and it is getting new shoots already.

Sounds like the grasses are fairly large and well developed if they have 3 ft of foliage now. I don't think you'll have a problem planting early September, if you plant properly and mulch them well. By now it's probably no secret that I'm a huge fan of fall planting :)

I've seen such great benefits from fall planting in so many zones that the risk is usually worth the reward. I say usually, because there is a risk involved. The risk, however, can easily be diminished with a little planning and some precautions. Yes, early frosts can always get the best of us, but a late winter snap can do the same in spring...and when soil has not warmed enough yet.

Check out these articles on fall planting...

http://www.santarosagardens.com/SearchResults.asp?Cat=379

http://www.santarosagardens.com/SearchResults.asp?Cat=635

http://www.highcountrygardens.com/library/view/article/103/

http://www.highcountrygardens.com/library/view/article/101/

As for the size and spacing of the Zebra grasses, I'd question the long-term wisdom of the Mall planting you saw. Zebra grass will be much happier with a bit of room. I'd hate to see you plant tightly for a massed sweep effect and in 3 years have to dig up large clumps. 4' or 5' on center is about minimum, but if you want to go tighter I urge you not to plant closer than 3' on center if you want them to be healthy clumps beyond the next 2 years. I tried planting Cabaret once in a tight sweep. It looked great for 2 years, then dead spots developed and it looks like a mis-shapen giant clump, not good form, and not healthy for the grass.

My 2 cents.