Welcome in advance! Early May would be a wonderful time to visit MD/DC. I can't recommend any botanical gardens, but if you are interested, we have a wonderful, thriving community garden that you are welcome to visit/tour, and many knowledgeable gardeners who are happy to share their experience. For information about it, our website link is listed below.
Hope this helps..

Here is a link that might be useful: Our Community Garden Website

THe wibsite www.marylandgardens.org lists 13 of the public gardens in Maryland. A couple are college campuses...I might not make a special trip to them but would stop if I was nearby. I have been to most of those gardens and several in the DC area if after you check out the websites you have more questions.

Happy visiting.

If the weather cooperates, that could be azalea time in DC. If so, the national Arboretum will have a beautiful display of Glenn Dale azaleas in bloom. And the bonsai museum is always worth a look in.

The azaleas at the National Arboretum are impressive. In Montgomery County,MD, Brookside Gardens and the smaller McCrillis Gardens are also beautiful. The link below for Brookside Gardens has a link to McCrillis Gardens.

Juliet

Here is a link that might be useful: Brookside Gardens

Thank you all for responding. I'm looking up the sites mentioned and I am printing out their locations. Thanks again. - Mike

Mike, Realtime recommendations are always good, but you should also take a look at the FAQ on this subject.

Here is a link that might be useful: Places to Visit

There's a nice place near me. Meadowlark Park in Vienna VA. It didn't seem to be mentioned in the FAQ. They charge to get in which is annoying and unusual for this area but it is quite nice.

The Mary Livingston Ripley Gardens in DC is tops on my list. The garden is next to the Museum of Industry, which is next to the Smithsonian Castle. Everything from hardy bananas to witch hazel, in interesting combinations. Most plants are labeled, often with hand-written signs by the gardener pointing out scents, colors, plant combinations, etc. So not only are there interesting new genera, species, and cultivars, but you see how they would look in a garden.

Downtown DC,and this garden in particular (it has lots of brick for heat retention) is zone 8, so by May it will be full of good stuff.

The whole area around the Museum of Industry and the Castle has many wonderful planted containers every year, as well as gorgeous container specimens of tender plants, and lots of these may be out by then, too.

May is the BEST time to visit Washington.

The area around the front of the Smithsonian Castle is the Enid Haupt Garden - it is a formal Victorian to match the architecture. I'll add another vote for the Mary Livingston Ripley Gardens - it's a nice place to sit with a picnic lunch when you're down on the Mall checking out the Smithsonian. The plant selections a fabulous. There is a similar garden along the north side (Capitol side) of the Natural History Museum that is intended to be a butterfly garden. Also the Botanic Gardens - close enough for you to sign in for a Capitol tour and then check out while you are waiting for your tour to begin. There is a decent garden around the new Native American museum too and their cafeteria is excellent, though as pricey as a restaurant.

I recommend the public Green Spring Gardens in Virginia, as they have a sale area behind the Visitor Center that is usually chock full of weird and interesting stuff that the staff has propagated. Green Spring essentially runs a garden fair every Saturday in May so check their website.

If you are here on the right weekend, Mount Vernon does a garden weekend and sells plants. Well worth the $11 admission to see the house, special re-enactors, garden tour, slave tour, and other programs. Their cafeteria is so-so and quite pricey, so it would be better to bring a picnic lunch and then splurge on dinner in Alexandria.

The Bishop's Garden at the National Cathedral is a bit off the beaten path for tourists since it is not on the Metro, but it is worth a trip if you are interested in the Cathedral. The boys and girls choirs sing almost every afternoon and that is free. The first weekend in May is the Garden Mart and it is fabulous. Lots of plant vendors, free entertainment, garden crafts etc. The Cathedral has its own Garden Center too, specializing in rare herb varieties. They have a website for you to check out.

If you get as far South as Richmond, VA we have several nice places to visit. The Lewis Ginter Botanical Gardens and Maymont Park are both wonderful. Lewis Ginter being newer and maybe more glitzy, but Maymont has some classic landscaping, and a mansion with a swan-shaped bed.

If you have a day I would suggest Longwood Gardens Kennett Square, Pa. It's 2-2.5 hrs by car from DC. It is one of the old DuPont estates, wonderful day.
The Philadelphia flower show will also be running March 5 >> 12. www.theflowershow.com
Hope this helps. Frank

Here is a link that might be useful: Longwood Gardens

mdgardengurl - Wow I didnt know the ranch club had a community garden. I will definitly have to check that one out.......

Carey

One of the fun/different things to do is to go on one of the GUIDED NIGHT TOURS at the Nat'l Arboretum (I know someone mentioned the loation already, but not this particular activity.) They take groups on a guided tour of the gardens at night--pointing out night time flowers, animals, etc. it's really quite magical (or romantic, if it's just you and the lovely lady!) You MUST sign up in advance--you can go to the Nat'l Arboretum website to do so. There is a fee, but it's worth it. This is also fun for tourists, since it takes place a night--when all the other traditional tourist venues (such as museums) are closed. So, you can fit MORE gardens into your visit here!!! I also see that they have an Azalea Collection Twilight Tour in early May--probably cool as well. (One word of caution--the Arboretum is in somewhat close proximity to some uglier parts of town, so be sure you know your map, and have good directions, so you don't find yourself lost.)

Here is a link that might be useful: Nat'l Arboretum Calendar of Events & Registration

The drive down to Mount Vernon along the GW Parkway has a good number of well formed tree specimens. You can stop off at the American Horticultural Society on the way, their HQ are here in Alexandria. If you are interested in dining in a colonial atmosphere, the Mount Vernon Inn at MV is actually a decent place to eat and not expensive (I live a few blocks away, disagree it being overpriced or bad). The Smithsonian's gardens previously mentioned are on the eastern side of the Mall area up to and including the Capitol building--this area is the hotstpot in the capital for gardens, no doubt. National Arboretum is also very nice, has extensive rhododendrum plantings which should be in bloom.

Here is a link that might be useful: AHS

I'll second the meadowlark gardens, we have a yearly pass and I go at least once or twice a month, very pretty setup, tons of plants with markers to identify them, and a nice walk around the park. The kids love it too.