The miracle flower of Peru, the four o’clock (or, as the French call it, “Belle de Nuit”), has been in gardens since the 16th century, when seeds were brought to Europe from the Peruvian Andes. Mirabilis jalapa caused such a stir in flower-and-garden circles that the original name for the genus was Admirabilis (from the Latin for wonderful), until Linnaeus changed it to Mirabilis.
The fact that single plants could bear flowers of different colors fired the imagination, especially since the miracle occurred without grafting other strains on the mother root (like the tomato/potato plant of today’s supermarket tabloids). And the flowers opened punctually around 4 o’clock in the afternoon (except in areas on daylight-saving time, where 5 p.m. became the rule). Finally, there was the perfume — a marvelous scent of sugar and lemony spice that varied from plant to plant.
The French were so excited by Mirabilis that the famous House of Worth actually designed ball gowns for women of fashion to wear at 4 o’clock parties, where everyone would stand around sipping champagne and waiting for the miracle flowers to open, upon which they would all cry out, “Mon Dieu!”
The species name, jalapa, is frankly a mistake. Pharmacists believed that the purgative jalap (named for the Mexican town Jalapa) could be obtained from the tuberous roots of four o’clocks. But that particular cathartic proved too violent, and the tuber’s only use today is in a dye that makes Chinese seaweed noodles look more appetizing.
The pioneering Austrian geneticist Gregor Mendel used the plants in experiments to prove that a single grain of pollen is sufficient to produce a viable seed. In the early 1900s, four o’clocks were seen to have variegated leaves. In one strain, the leaves were mottled dark green and yellowish white due to variations in the chlorophyll in individual plant cells; where two zones of color met, there would be a band of cells that contained both colors. Experiments showed that seed produced by flowers on green branches yielded green plants, regardless of which pollen was used for fertilization. Flowers from variegated branches yielded seedlings that were green, variegated or white. Thus plastids, or cell bodies, could be unaffected by chromosomal genes.
But history aside, four o’clocks are wonderful plants for the evening garden. They form little bushes, covered with flowers and often reaching a height of 3 feet. A number of colors are available — including red, yellow, white and rose — and many flowers will be striped or dashed with other colors.
In tropical America, four o’clocks are perennials. If left alone, they’ll soon form tuberous roots weighing up to 40 pounds. Here in our temperate gardens, these black tubers can reach the size of a baked potato. If dug in the fall and kept in a warm, dry place over the winter, they can be planted out the next spring as soon as the ground warms, just like a favorite bulb. On the other hand, self-seedings from four o’clocks grow quickly, and by the end of the second season, the tubers lose some of their resiliency and produce smaller plants.