More trees (and free)
If you think I’m crazy to suggest a visit to the cherry blossoms around the Tidal Basin with everyone else in the world, but like the idea of walking around with plants and trees in bloom, then consider the National Arboretum. While not directly metro accessible, you can take the X6 Metrobus from Union Station or you can drive (there are two entrances). It’s free and there’s plenty of free parking.
Here’s what’s typically in bloom in April:
lst week: Daffodils, crocuses, early magnolias, Korean azalea, Japanese-andromeda, forsythias, cornelian-cherries, woodland wildflowers, epimediums
2nd week: Daffodils, crocuses, early magnolias, Korean azalea, Japanese-andromeda, forsythias, early azaleas, Oconee-bells, epimediums
3rd week: Daffodils, magnolias, Japanese-andromeda, forsythias, Japanese-quince, early crabapples, flowering cherries, azaleas, woodland wildflowers, spring-blooming camellias
4th week: Magnolias, crabapples, azaleas, early rhododendrons, daffodils, Japanese-quince, woodland wildflowers, spring-blooming camellias
There are two particularly cool sights at the arboretum: the National Capitol Columns and the National Grove of State Trees. There are also picnic tables in the grove, but no cooking is allowed.