The moonflower (Ipomoea alba) is an annual vine closely related to the morning glory. The flowers open in the late afternoon and remain until early morning, sweetening the evening air with fragrance. They are pollinated by moths, but I've found the blossoms covered by dozens of bees on late summer evenings, buzzing from one flower to the next. The flowers are trumpet-shaped and the leaves like hearts.
Moonflowers like full sun and rich, moist, well-drained soil. Plant them in a spot where you can observe their silvery beauty by moonlight or near a window to enjoy the scent indoors. We grow ours in pots and along the fence surrounding the pond, where the vines twine in between the pickets and the blossoms unfurl just as the sun begins its descent.
Moonflowers are easily confused with Brugmansias and Daturas. Some of the seedlings we bought this spring were mislabeled as Angel's Trumpet's (Brugmansia), but once these started growing, it was clear they were Moonflowers and not Angel's Trumpets. The others haven't begun to bloom yet, but I'm wondering if they're not Daturas, again mislabeled. Moonflowers can be planted with other evening-blooming flowers to extend your enjoyment of the garden into the twilight hours.