Wild Four-O'Clock (Mirabilis nyctaginea)
Four-o'clock Family (Nyctaginaceae)
Allionia nyctaginea, Oxybaphus nyctaginea, Oxybaphus nyctagineus, heart-leaf four-o'clock, heart-leaf umbrella-wort, snotweed, umbrella-wort.
Origin and Distribution:
Wild four-o'clock is a native species of the Midwest and northern Great Plains, and has become locally naturalized in the northeastern states. Though its distribution as an agronomic weed is rare, reports indicate that it is becoming more common throughout the Midwest. This species is commonly found in pastures, prairies, roadsides, gardens and wasteplaces, but has recently been observed to invade no-till corn and soybean fields. Wild four-oâ€™clock can grow in a variety of soil types, ranging from gravelly to rich.
Wild four-o'clock is an erect bushy perennial, characterized by its large fleshy taproot, swollen joints and smooth heart-shaped leaves that resemble lilac leaves. It reproduces by seeds.
The large, tough, fleshy taproot is branched, and can extend down more than 20 inches in the soil.
Seedlings and Shoots:
Cotyledons are irregularly round, often flat-ended, somewhat concave and of unequal size. The underside of cotyledons and true leaves is often tinged with purple. The first true leaves are egg-shaped, but subsequent leaves are increasingly heart-shaped. True leaves have short hairs on the margin.
Several stems can emerge from a single taproot, and grow 1 to 4 feet tall (sometimes up to 6 feet). The smooth stems are highly branched, often 4-sided (though they are not as distinct as species in the mint family), and sometimes ridged. The swollen nodes along the stem are very distinctive, resembling a ball and socket joint. Stems typically separate at the nodes at the end of the season.
The leaves are opposite, egg- to heart-shaped, pointed, and smooth on both sides and on the margins, resembling leaves of lilac. Leaves are 2 to 4 inches long and 1 to 3 inches wide. Leaf stalks are present on lower leaves, but may be absent on upper leaves.
Flowers of wild four-o'clock are borne in clusters of 3 to 5 at the ends of branches. The small, tubular or bell-shaped flowers are composed of sepals (outer floral leaves), which are fused below and open above, and can be pink, purple, white or yellowish. Flowers lack true petals, and the petal-like structures are actually the upper ends of the sepals. Five large, veiny green bracts (specialized leaves) are fused to form a cup around the flower cluster. As seeds form, bracts enlarge and split open to almost 1 inch wide, becoming tan and papery.
Fruits and Seeds:
The seeds (1/8 to 3/8 inch long) are egg-shaped, hairy and grayish brown, with 5 lengthwise ribs.
The small flowers of wild four-o'clock bloom from May to September, and are very short-lived. They open late in the afternoon, last through the night, and wither the next morning. Viable wild four-o'clock seeds are produced as early as mid-June. The papery bracts surrounding the seeds may aid in dispersal, especially by man-made vehicles. The swollen stem joints of wild four-o'clock resemble a ball and socket joint. The lower stem forms the socket, or cup-like structure, that the upper stem, or ball, sits in. This joint structure is particularly noticeable at the end of the season when stems separate at the nodes.
Wild four-o'clock spreads to new places by its seeds, which can hitch rides on vehicles and infest crop seeds and livestock feed. This species is highly tolerant of 2,4-D. However, good control can be obtained using mechanical methods. For very small infestations, digging up plants is effective. Wild four-o'clock is nearly impossible to pull up, because the stems readily break off at the root crown, only to sprout again. One local Amish farmer reported that pigs fed on the taproots and could keep the weed controlled. When pigs were removed, the weed began to spread to corn and soybean fields. For larger infestations, repeated mowing reduces seed production and weakens plants over time. Effective control can be obtained by several years of clean cultivation.
The roots and seeds contain a toxic alkaloid, and can cause stomach pain, vomiting and diarrhea in children. However, a local Amish farmer reported that pigs are very fond of the fleshy taproot.
Facts and Folklore:
The scientific name roughly translates to 'wonderful night-bloomer'. The common name, 'wild four-o'clock', refers to the time of day that this species will flower (around 4 pm).
Another common name, 'umbrella-wort', refers to the large papery bracts which form an 'umbrella' around the flower clusters and seeds.
Several Native American tribes used the root to reduce fever, cleanse wounds and relieve abdominal swelling.