The problem I have with the discount stores is some of the stuff they sell is not appropriate for growing in the are where the store is located. Mainly that means that they sell stuff that is not hardy. For example I have seen evergreen holly sold at a discount store in northern Minnesota. They also sell some plants that are really not approproate for the average house lot. At Home Depot once, the place was stuffed full of Silver Maple and Sycamore trees. I wouldn't put one of those on my 0.2 acre lot.

With that said, they do offer good prices on a lot of the tried and true basics that should do well where you live. Things like Burning bush, hostas, echinacea, arborvitae etc. So I would see what they have and if you are not sure about it, do a little research before you buy. Unfortunately at many of those stores, there won't be anyone with the knowledge to properly answer any questions you might have.

The plant quality varies from store to store, even within a chain. It depends on the managers and knowledge of staff, how much to water, appropriate methods and places for stocking, etc.

I would say that once you are sure the particular plant is appropriate for you, if you can see its condition, there's no reason not to buy it there. What I'm leery of is plants purchased in dormancy - it's hard to tell if they're alive. Like root perennials (hostas, dicentra, etc.) where you get a bag of peat moss and hope there's a living root ball inside. Or bagged, wax coated roses. IMHO, this is still preferable to ordering perennials from iffy mail-order catalogues. I have been burned far far more times by mail order than bargain shopping.

Have fun with your new garden!

I agree, make sure it's alive, or showing signs of life before you buy it. If I am buying those perennial roots in a plastic bag of peat moss, I try to see if I can see any sprouting going on in the bag (yeah, they love me as a customer as I am searching through the lot). My pet peeve is those discount stores clearing out those carton bare root roses, in July, sitting in the hot dry sun, and the roses don't have any signs of growth.

Most discount stores carry the more basic varieties at good prices. If you are knowledgable about various hardy plants it helps. Else, maybe make a trip, write down the plants they do have and research on the internet before buying.

As for discount stores buying inappropriate plants for an area, our nurseries sort of do this as well. The difference is that the nursery lets you know ahead of time that the item isn't fully hardy for your area, at least that's what our nurseries do here.

I like when discount stores carry some out of zone items, however, it allows one to buy an out of zone plant cheaply and experiment. But, I do feel for unsuspecting customers who just figure "because they sell it, it must be hardy". Also, if they offer any advice at a discount type place (that's just set up for the season), I take it with a grain of salt and do my own research, which is easy enough to do. Type a plant name and search on the internet. You'll get loads of information. Not all the information might be accurate, but if you view 15 or so websites you might get a general idea of a plant.

Glen

I find that if you buy early in the season, the plants at the discount stores are just fine.
Such stores are less likely to spend a lot of effort on maintaining them and so, as time passes, containers dry out or plants get rootbound. (unfortunately, that is also true for our local Home Depot store)
Discount store staff aren't hired for their green thumb and seem run off their feet helping customers during this season. I've seen shade plants piled up in full sun and sun plants stored under shelves. Look for any insect pests and fungus - overcrowding and overwatering can encourage that.

After the first few weeks of the gardening season I don't bother with the discount places any more to find quality plants - you can however, find some super bargains if you're willing to play nurse for a season.
A sad-looking 99-cent 'annual larkspur' turned out to be an absolutely stunning, reliably blooming delphinium for me.