Lots of places. For me, the local resources are generally more expensive than mail order, so a lot of what I buy is online. Two good resources for perennials are Bluestone Perennials (small plants, but always does well, have money back guarantee and excellent customer service) and Green Mountain Transplants (excellent small plants, more interesting selection than Bluestone, but forget about customer service or guarantees). Just about all of my roses have been bought online, since no one around here (except for Heritage Rosarium in MD) sells antique roses. I'm also restoring my woodlands, so the native plants I'm buying are also mostly coming from online resources (Prairie Moon, Pine Ridge and Arbor Village). Fairweather Gardens and ForestFarm are expensive but excellent resources, and there are tons of good vendors online.

If you are going to order online, please check out the vendor first at Garden Watchdog at Dave's Garden. Basically, people report on their buying experience from various vendors, and it is an *excellent* resource.

I also receive a lot of wonderful plants at the local swaps (Mid-Atlantic Swap in Burtonsville, MD was on May 5th). And those are of course, free. Just comes attached with memories sometimes.

Here is a link that might be useful: Garden Watchdog