It was not that long ago I learned about buying plugs rather than quart and gallon sized perennials. Plugs are great for when you need many perennials and the cost of larger quart or gallon sizes would be prohibitive. If you are not familiar, plugs are small, typically 2" plants, that come in trays.
My experience is that plugs are easier to get established after planting. If you are planting in tight spaces or under a tree, the small sizes can be planted without disturbing other plants or tree roots. They are also ideal for filling in a newly cleared area or converting an area from grass to garden.
Best of all, after two years, perennials planted as plugs are just as large and seem to be stronger than perennials planted as quart size. I am completely converted! While I have rarely seen plugs available in nurseries and garden centers, they are readily available by mail.
Izel Plants sells plants from several mid-atlantic nurseries so plants are acclimated to Chesapeake watershed conditions. Their excellent website provides size availability (ranging from plug trays to bare root to quarts) and shipment date for your zip code.
Prairie Nursery in Wisconsin sells only native plants and has a number of natives that are harder to find. Their helpful website includes loads of information about each plant, conditions and a map of the native range of the plant. It's particularly helpful for us in the Chesapeake watershed to be able to search by clay soil. They also allow you to mix and match plug trays, helpful if you don't want 32 of the same plant. Check out their pre-planned gardens for different situations.
Prairie Moon Nursery in Minnesota has an extensive on-line store of native perennials, ferns, grasses ground covers and some shrubs. Many are available in 2" size plants in trays of 38. You can search by condition. type of plant or soil type. They also provide mix and match trays.
Finally, a new mail order nursery has been added to Nuts for Native's "Where to Buy Native Plants." Direct Native Plants, a wholesale nursery in Middle River, Maryland, recently started to retail by mail. Direct Native Plants sells native perennials. shrubs and trees. Plants have excellent root systems and arrive quickly. It's always great to have another source of high quality natives.
I should probably add that Nuts for Natives has no affiliation with these nurseries. The Nuts for Natives purpose is to encourage people to try native plants — for fun, to enhance your garden and to nourish your soul.
For more info: Handy tips from Pairie Nursery for planting your plugs.