Vandermeer Nursery has supplied the vast majority of the plants I've put into my garden project... done over a period of the past 12 months. They sell good quality plants and have a wide selection for all your needs - their system will tell you which are shade/sun/butterfly garden friendly/native. Their prices are average but the quality is better than average. I've tested their return policy with a couple of items after this past brutal winter and they cheerfully provided a credit (keep your receipt and return the dead plant) ... and 18 months is significant for a return policy!
You will have better results because they source locally - what that means is that the plant you buy is grown in Ontario and won't easily go into shock or die when winter comes. I've recently learned that big box stores import plants from the US so the first cold winter they have is in your garden... much higher failure rate! When you're buying perennials, shrubs, and trees, that matters more than you imagine.