So, where do I find unusual plants and rare perennials? More than likely the best answer to that question is mail order nurseries. Mail order nurseries fill a niche brick and mortar stores cannot. They are capable of staying afloat while offering large selections of rare and unusual perennials. Instead of relying solely on the business of locals like a physical retailer, a mail order nursery gets business from the whole country.
Think about it this way...if 1% of gardeners buy a certain rare plant from local retailers they might sell 100, but a mail order nursery might sell 1,000 or more of the same plant because they are selling to a larger base population. Not only can mail order nurseries take advantage of larger populations they can also take advantage of a larger range of tastes and climates. If you want unusual boutique ice cream you probably won’t find it locally in the winter in northern Alaska, but there are mail order companies who will gladly ship it to you so you can enjoy bacon jalapeno ice cream wherever you might be. If you're a palm lover who lives in New England it’s not a problem. You can get it shipped to you.
Some mail order nurseries, like Plant Delights Nursery, even work to find and breed plants that will tolerate the climate wherever you might be and whatever your tastes. That New England palm lover can order some palms that will tolerate the cold as far north as parts of Massachusetts, and they make good potted plants. So, if you are looking for rare plants for sale , your best bet is to shop at mail order nurseries, especially those who specialize in rare and unusual plants, like Plant Delights Nursery.