Southwest Desert Flora

Nyctaginaceae, Four O'clock Family

Members of the Nyctaginaceae family or Four O'clock Family are widely distributed primarily in tropical and sub-tropical areas, although some species are found in temperate regions including the southwest and elsewhere throughout the United States. They may be herbs, shrubs or trees.

The leaves in this family are simple, entire, exstipulate, and usually opposite.

The family contains several unique family characteristics. Individual flowers are apetalous with small tubular petal-like structures called the perianth. The true “petals” are replaced by colorful, fused leaf-like bracts. The fruit in the Nyctaginaceae are called "anthocarps".

The fruits may be dry, fleshy or covered with sticky hairs and in some members the persistent calyx bears sticky glandular projections that stick to the bodies of animals and thus aid in seed dispersal. Other unique survival strategies include the ability to self-pollinate without opening (cleistogamous). Some species have the ability to grow in soils with high concentrations of gypsum (gypsophily).

Important species include the root crop of Mauka (Mirabilis extensa) which is of local use in the Andes. The four-o’clocks (Mirabilis jalapa), sand verbena (Abronia umbellata), and South American Bougainvillea (Bougainvillea glabra, Bougainvillea spectabilis) are widely cultivated as ornamentals.

Four O'clock are so named because the flowers open late in the afternoon and are closed by morning.

The Plant List includes 1,420 scientific plant names of species rank for the family Nyctaginaceae. Of these 450 are accepted species names.