Description

Mirabilis jalapa (The four o'clock flower or marvel of Peru) is the most commonly grown ornamental species of Mirabilis. It is from tropical South America, with flowers in a range of colours. The plant has become naturalised throughout tropical and warm temperate regions. In cooler temperate regions, it will die back with the first frosts, regrowing in the following spring from the tuberous roots. The plant does best in full sun, and the roots should be soaked before planting. In North America, the Four O'clock perennializes in warm, coastal environments, particularly in US Zones 9-10. The flowers usually open from late afternoon onwards, hence the first of its common names. In China, it is called the "shower flower" or "rice boiling flower" because it is in bloom at the time of these activities. A curious aspect of this plant is that flowers of different colours can be found simultaneously on the same plant. Carl Correns used the four o'clock as a model organism for his studies on cytoplasmic inheritance. He used the plant's variegated leaves to prove that certain factors outside the nucleus affected phenotype in a way not explained by Mendel's theories. When red-flowered four o'clock plants are crossed with white-flowered four o'clocks, pink-flowered offspring, not red, are produced. This is an exception to Mendel's Law of Dominance. The seeds of the 4 o'clock are spherical, wrinkled and black upon maturity. They start out greenish-yellow and darken over time. The plant will self-seed, often spreading rapidly if left unchecked in a garden. The flowers produce a strong, sweet-smelling fragrance. Despite their appearance, the flowers are not formed from petals - rather they are a pigmented modification of the calyx. The flowers attract hummingbirds and moths, which pollinate the plants.