For a blizzard of beautiful white flowers in the afternoon, plant this one. When frost threatens, you can dig the bulbous roots that will have formed, and save them (like dahlias or glads) for next spring.
About the Four O'Clocks or the "Marvel of Peru." This wonderful tropical wildflower has been gracing gardens for centuries. Your grandmother probably grew it, and knew the big secret of the older seeds. They are famous for rapid growth and producing glossy-leaved plants having flowers in several colors--on the same plant!
The names tell the story. The blooms open in the afternoon, thus the common name "Four O'Clock." And the botanical name, Mirabilis jalapa should tell you the plant comes from a Spanish-speaking area. "Mirabilis" means "wonderful" in Latin, and the Spanish-appearing "Jalapa" (the j is pronounced as an "h" in Spanish) is a town in Mexico.
Then there's that other common name: "Marvel of Peru." This exotic descriptive name tells you the plants grow wild in the Andes, and the "Marvel" part refers to the fact that they do produce flowers in several colors on the same plant. Seeds were sent to Europe by Spanish explorers in the 1500's.
In your garden, you have a choice of which color(s) you want to grow. Yes, the wild plants do have flowers in several colors, but they're rangy, somewhat weedy plants, too. The hybrids we plant today are organized by color and make neat, bushy growth, rarely over about 24."
The bulbous roots. Four O'clocks grow rapidly from seed, and another curious thing about this annual is that they quickly form a bulbous root, much like the common potato. In frost-free places (like Miami), they can be left in the ground year-round, and these big roots simply grow larger and larger over the years. Where there are freezes, the "bulbs" can be lifted in fall, and replanted in spring, giving you large, rapidly developing plants and lots of quick color.