The Herring Run Nursery up in Baltimore will host two more plant sales this fall on October 9 & 24.
I love this organization because they are doing great things with native plants in a very urban area of Baltimore, my hometown. Although it is a bit of a drive from DC, it is worth it when you consider that your plant purchases help a great local non-profit.
Their nursery has a sizable selection of native trees, shrubs, and vines and a limited selection of native perennials. Sale times are 12:00-4:00 PM for both dates. (For an up-to-date plant list you can visit their website or call 410-254-1577 ext 104.)