Where to Buy Plants: Big Box vs. Nursery vs. Catalog/Internet

Figuring out the best place to buy plants can be difficult. Some gardeners refuse to buy from the big box garden centers (ie Home Depot, Lowe's). They're convinced that they'll get better quality at a retail nursery. Having worked at a couple of private retail nurseries, I can say that even there plants occasionally had bugs or got dried out (sometimes I was the one who forgot to water them . . . oops). My experience has been that you can get healthy or unhealthy plants almost anywhere. The key is to choose plants - from whatever source - that look healthy. Avoid plants that look dried out or that have bugs or mildew or another pest visible. Many garden center stores offer a 1 year guarantee, so keep your receipts in case of disaster.
Here are a few pros and cons for each source:
Big Box Garden Centers (Lowe's, Home Depot, Ace, WalMart) - These stores usually carry the most popular, common plants for your area. If you're looking for a rare plant, you probably won't find it here. Or if you need good plant advice, you usually won't get it here. For example, in my area these stores sell loads of azaeleas without warning their customers that these shrubs need acidic soil and will look sickly if planted in our alkaline soil. Don't buy plants that are wilted or look sickly - unless the store has a 1 year guarantee and you want to take the chance of having to return the plant if it gives up the ghost.
Prices are usually one half to one third of the price of private retail nurseries. For example, when I lived in California I found the exact same "Confederate Star" jasmine vine, 1-gallon size, at Home Depot for about $5 and at a private retail nursery for $15. The difference in price adds up even faster when buying trees (ie $70 at Home Depot vs. $125 at a private nursery for a similar sized tree). If you have a limited budget - as I do - then garden centers are a great choice for buying common plants.
Retail nurseries -
Local retail nurseries often carry a wider variety of plants than big box stores. New and improved cultivars often show up here before they're available at the big box stores (if they ever become available via big box stores). The prices are higher, but the employees or owner can usually give you good advice about plant selection and care. There may or may not be a guarantee for their plants. Sometimes there is a volume discount available. If you are budget conscious, and have a list of plants to buy, I'd recommend stopping at a big box garden center first. Then go to a private retail nursery to get the plants that you can't find at the garden center . . or else order from the next catagory: a catalog/website.
Mail-order Catalog/Website Orders -
Catalogs and websites offer the greatest variety of plants. Some exciting new cultivars may be available only from the specialty nursery that has developed them - and if that nursery isn't in your town, then you'll have to order from their website or catalog. It's easy to sit at home and order, then have them delivered to your door. Obviously shipping costs are the limiting factor here - so most plants will be very small when they arrive. That's fine for bulbs or quick-growing perennials, but isn't as good for shrubs, trees and vines. Before ordering from a new company, I like to check their ratings at www.davesgarden.com in the Garden Watchdog section. Companies should fix the problem quickly and politely if plants arrive in poor condition.
I've ordered from the following companies and been pleased. The kind of plants I've ordered are in parentheses. Type the company name into google to find the website.
David Austin Roses (bare root roses)
Bloomin' Designs Nursery (daylilies)
Dutch Gardens (bulbs, perennials)
Springhill Nursery (bulbs, perennials)
White Flower Farm (bulbs, perennials)
Jackson and Perkins (bulbs, perennials)
Joe Pye Weed Gardens (siberian iris)
Dowdeswell's Delphiniums (delphinium seeds)
Park Seed Company (seeds, perennials)
Burpee (seeds)

Happy buying!