I have updated my list of public gardens and demonstration gardens in the Washington DC metro area, see tab with same name on my website, pegplant.com. Many of these places are perfect to take the kids and visiting friends and family to this summer.
Public gardens are living examples of which plant performs well in the area. Many public gardens have a reference library, gift shop, web site, and gardening hotline. Usually, public gardens host seminars, workshops, classes, events, and plant sales. They may publish their own books on plants for the area or distribute free handouts. Some have staff horticulturists who can identify plants or answer questions.
Demonstration gardens are a great way to learn what works in our area and how to manage our local issues, such as deer. The gardens are open to the public, every day, from dawn to dusk, free. Each county that has a Master Gardener program usually has at least one demonstration garden, managed by the volunteer Master Gardeners.
If you have suggestions for additions, feel free to send them to me by commenting on this post.