2. Mirabilis L. (umbrellawort, four-o’clock)

Plants perennial herbs, sometimes slightly woody at the base, the roots woody (somewhat tuberous in M. nyctaginea). Stems erect or ascending, glabrous or hairy, sometimes glaucous. Leaf blades variously shaped, the margins entire or nearly so, glabrous or hairy. Flowers sessile or minutely stalked in small clusters at the ends of inflorescence branches, the overall inflorescences terminal and appearing as dense clusters, umbels, or less commonly small panicles, and/or sometimes as solitary, long-stalked flower clusters in the leaf axils. Each flower cluster with (1)2–6 flowers, subtended by a calyxlike involucre of fused bracts, this broadly bell-shaped at maturity, with 5 broad shallow lobes, persistent and becoming enlarged, somewhat flattened, and somewhat papery at fruiting. Perianth 5–10 mm long, white, pink, or reddish purple, the expanded portion bell-shaped to saucer-shaped at flowering, the lobes notched at the tip. Fruits (including the hardened perianth tube) narrowly obovoid to narrowly ellipsoid, bluntly 5-angled or ribbed, variously ornamented and hairy. Forty-five to 60 species, North America to South America, Asia.

Mirabilis jalapa L. (common four-o’clock) is a perennial neotropical species that is commonly cultivated in the United States as an annual bedding plant. It has 1-flowered, deeply 5-lobed involucres and flowers with the perianth 3–6 cm long. Because this species has tuberous roots and can seed itself, it may eventually be recorded as an escape from cultivation in Missouri.

The Missouri species are part of a confusing complex of about 25 species that is treated as Oxybaphus L’Hér. ex Willd. in some of the older literature, one of several genera sometimes segregated from Mirabilis. These species have broadly bell-shaped shallowly lobed involucres that tend to become enlarged at fruiting and subtend (1)2–6 flowers, flowers with the calyx tube not elongated, and fruits with the outer surface tending to turn gelatinous when wet. The common name “four o’clock” refers to the flowers opening in late afternoon, and our species tend to begin flowering from late afternoon to early evening, with flowers withering early the following morning. Taxonomy of the group is based mostly on characters of the fruits.