If the temperature is reasonable and the sun is out, I'd recommend spending a day at the National Arboretum. Really, you'd need more than a day to see everything in this expansive park, which covers nearly 450 acres. When you arrive, stop at the visitor's center (located at the R Street entrance) and pick up a map of the grounds so that you can figure out your "must-see" spots.
The Arboretum was established in 1927 by an Act of Congress to allow for educational programs, floral and plant displays for the public, and research.
Admission to the Arboretum is free; hours are 8am to 5pm daily. There are no close metro stops, unfortunately. Driving is the easiest option (see website for directions). If you're confined to public transportation you can take the metro to the Stadium Armory stop and an R2 bus from there to the gardens.
At the southern end of the Arboretum is the National Grove of State Trees, which, as the name suggests, includes state trees from all 50 states and DC. It's interesting to explore the area and happen upon trees from different states, as they're in no particular order. The Grove was founded in 1989; many of the trees, as a result, are still fairly small.
We found this area to be somewhat unkempt compared to other parts of the Arboretum. Apparently, there was a plan to connect all the trees with a pathway that was never built due to budget shortages. As a result, the trees stand in clumps in overgrown grass.
It seems that not many people bother to see this section of the Arboretum, so if you do go you'll probably have the place to yourselves. There's a parking lot out front and some picnic tables if you decide to bring lunch along. At the entrance from the parking lot you'll also see a semi-circular panel with ceramic tiiles naming the trees of each state.
In late April/early-mid May, the Azalea Walk is a must. This area of the Arboretum is filled with azaleas of every shade; it's hard not to go a little photo-crazy here. Most of the azaleas are along dirt trails that take you through wooded areas, although there's also a more formal garden (the Lee Garden). Be sure to leave at least 45 minutes to see the area, and wear good walking shoes. There are some steep areas, although the walk is generally appropriate for all ages.
Next to the visitor's center is the wortwhile bonsai (Japanese) and penjing (Chinese) plant collection. The collection dates to 1976, when Japan gave the US over 50 bonsai as a bicentennial gift. The most prized bonsai at the Arboretum dates to 1625 and survived the bombing of Hiroshima in World War II.
Surrounding the bonsai collection are Chinese, Japanese and North American pavilions, each of which is a peaceful and unique garden that makes for a pleasant stroll.
One of the more unexpected areas of the Arboretum is the grouping of 22 sandstone columns standing in an open field. Prior to their life in this field, the columns supported the dome of the National Capitol building, but were replaced in the mid 20th century. The columns were added to the Arboretum landscape around 10 years ago. A reflecting pool was built in front of the columns, making it even more picturesque.
The US National Arboretum is one of Washington's best--and least visited--attractions. It has some spectacular gardens, representing various temperate plants from all over the world. They include exquisitely beautiful Asian gardens, bonsai trees, herb and vegetable gardens, a grove of trees with one from each state, and the largest collection of conifers that I've ever seen. It also has a wide range of youth programs and other activities. A definite must-see for the "green thumb."
In the background of the third photo are the Capitol Columns. They were once part of the US Capitol Building, but were removed in the 1950s.
The National Arboretum is a wonderful exhibit of flora native to the United States and examples of plants from around the world.
One of the must see exhibits at this little visited park is the Bonsai Museum. On display are dozens of delicate and beautiful bonsai trees displayed in three pavilions. The core of the exhibit is a wonderful collection of trees, some nearly 300 years old, that were given to the United States as a gift from our good friends in Japan. There are also Chinese Style Bonsai and truly beatiful examples of American Bonsai Trees.