The Floral Library is a flower garden patch planted by the National Park Service next to the Tidal Basin. It consists mainly of several varieties of tulips, but there are also daffodils and other flowers.
The tulips typically bloom a bit after the cherry blossoms, so it's a good option if you arrive a bit late for the cherry blossoms.
How to Find It
It's located right next to the Tidal Basin, next to the northern end of the Maine Ave parking lot (the opposite end of the parking lot from the paddle boats). If you're trying to get your bearings, it's on the corner of the Tidal Basin closest to the Washington Monument.