Wild Four O'Clock

Mirabilis nyctaginea

Wild Four O'Clock

Family: Nyctaginaceae

Other Common Names: heart leaf four o'clock
Weed class: A
Year Listed: 1989
Native to: Native east of the Rocky Mountains, from Montana to Mexico, and east to Wisconsin and Alabama
Is this Weed Toxic?:

not known to be


Legal listings:

WA Quarantine list, WAC 16-750

Why Is It a Noxious Weed?

It is a weedy plant that is capable of establishing in a wide range of habitats. In Washington it has shown the ability to spread from a small 10 acre site to several hundred acres. It is capable of impacting agricultural and range lands.

How would I identify it?

General Description

It is a perennial herb, sometimes woody at the base, reaching 3 to 4 feet tall. It has a thick, black taproot that can extend downward for two feet. The name refers to the flowers, which open late in the day and whither early the next morning.

Flower Description

Flowers are about 3/8 in diameter and are in clusters of 3 to 5 growing from a short, hairy flowerstalk at the tips of the plant. A whorl of bracts is found at the base of each flower. The flowers have 5 reddish to lavender sepals and no petals.

Leaf description

Leaves are oppositely arranged, heart-shaped to egg-shaped and 2-4 inches long and 1-3 inches wide. The lower to middle leaves are attached by a petiole (leaf stem). Upper leaves may be sessile (no leaf stem). Leaves are waxy and usually hairless.

Stem description

The plant’s overall shape is bushy and the stems are oppositely branched (pairs of branches along the stem). The upper stems and leaves are sometimes glaucous (covered with a whitish or bluish waxy covering).

Fruit Seed Description

Seeds are prominently five-ribbed, warty, somewhat hairy, grayish brown in color and ranges from 1/8 to 1/4 inch in length.

Where does it grow?

Wild four o'clock is found in a range of habitats in eastern Washington, including orchards, alfalfa fields, rangeland, right-of-ways and disturbed areas. It can also grow along riverbeds, and in sandy, rocky, and heavily cultivated soils. Please click here to see a county level distribution map of wild four o'clock in Washington.

How Does it Reproduce?

It reproduces by seed and by fragmented root pieces. Seed is set from July to September. The involucre aids in the dispersal of the seeds, acting as a small umbrella which catches on vehicles.

How Do I Control It?

General Control Strategy

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Mechanical Control

Hand pulling is not recommended because the stems break at the crown. The roots are strongly branched, and broken root pieces will produce sprouting. Small infestations can be spaded or dug up. Repeated mowing or cultivation will prevent seed production and lower the seed bank. Eventually the plant will die from loss of nutrient reserves stored in the root. Plow infested meadows and plant a cultivated crop for 2 years. Hoe out remaining plants.

Cultural Control

Field corn does compete well with wild four o'clock.

Herbicide Control

Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.

For More Information

See our Written Findings for more information about wild four oclock (Mirabilis nyctaginea).

See our postcard for early detection information about wild four o'clock.

Invasive.org webpage on wild four-o'clock

Additional Photos