PNW363 Wild Four O'Clock (Mirabilis nyctaginea (Michx.) MacM.)

Wild four o'clock, also Fremont) have reported wild shaped leaves resemble lilac known as heart-leaved four o'clock in Idaho. leaves. Pink-purple flowers umbrella wort, is a weed of Oregon has not reported occur in clusters of three to uncultivated land. It is finding this weed. five on forked branches near native to the Midwest and Wild four o'clock is a class A the top of the plant. The five northern Great Plains of the weed on the Washington petals of each flower fuse United States. In Washing­ State Noxious Weed List. It together to form an open ton, it grows in an alfalfa is not listed as a noxious tube, about 3/8 inch in field, pasture, rangeland, weed in Idaho or Oregon. diameter at the opening. pear and apple orchards, The bracts that surround the and along roads in IDENTIFICATION flowers become enlarged Okanogan County, near and reddish-colored with Loomis, Okanogan and Wild four o'clock is a age and form the "umbrella" Tonasket. Scientists member of the four o'clock that usually carries three collected wild four o'clock family, Nyctaginaceae. The seeds. The hairy grayish in Spokane County in 1981, name refers to the flowers brown seeds are cylindrical but have not found it there that open in late afternoon club-shaped nutlets with since. Three Idaho counties then wither the following five prominent lengthwise (Bonner, Nez Perce, and morning. Several stems, ribs. Each seed is 1/8 to 114 ranging in height from 1 to 3 inch long. feet, arise from a large, It is easy to confuse sticky tough, fleshy taproot. Both geranium, a native plant, leaves and stem branches are with wild four o'clock, opposite. Smooth, heart- because the flower color is

Wild four o'clock stems and Pink-purple flowers are borne Bracts surrounding the seeds leaves are opposite and smooth. in clusters at the top of the form an "umbrella" that assists Heart-shaped leaves resemble plants. in their transport. lilac leaves.

A Pacific Northwest Extension Publication • Washington • Idaho • Oregon similar and plants may be In its native region wild four the Extension Offices of about the same size and o'clock grows on roadsides, Oregon State University, shape. Sticky geranium along railroads, in prairie Washington State University leaves are palmately lobed, land, dry meadows, fence and the University of Idaho. rows, groves, gardens, and not heart-shaped, and the The author acknowledges occasionally in pastures and whole plant is covered with the support of the Washing­ sticky glandular hairs. In small grain fields. ton State Department of contrast, wild four o'clock Agriculture and the has smooth surfaces. CONTROL Washington State Noxious Three native four o'clock Wild four o'clock seeds are Weed Control Board in species grow in the Pacific carried by vehicles and preparation of this bulletin. Northwest, including equipment and appear in By Cindy Roche, M.S., Washing­ Mirabilis linearis, M. crop seed and livestock ton State University Extension bigelovii, and M. macfarlanei. feed. Preventing seed Coordinator, and Plant Scientist in Mirabilis linearis has narrow spread is especially Natural Resource Sciences. linear leaves and occurs important, because wild Pacific Northwest cooperative mostly east of the Rocky four o'clock has limited Extension bulletins are joint Mountains. Upper portions distribution. Control of publications of the three Pacific of M. bigelovii plants are established populations Northwest states-Washington, densely covered with fine depends on the type of site. Oregon, and Idaho. Similar crops, hairs. It grows from To reduce wild four o'clock climate, and topography create a Malheur County, Oregon, natural geographic unit that by pulling is nearly crosses state lines. Since 1949, the southward. Flowers of M. impossible, because the PNW program has published over macfarlanei are larger than sterns break off at the crown 350 titles. Joint writing, editing, those of wild four o'clock and the roots resprout. and production have prevented (about 1 inch in diameter). Although digging plants is duplication of effort, broadened Its seeds have 10 ribs. laborious and the availability of faculty Mirabilis macfarlanei grows specialists, and substantially time-consuming, it is reduced costs for the participating on rocky slopes in the Snake effective for scattered plants states. River Canyon and lower and initial infestations. Salmon River in Idaho and Issued by Washington State Repeated mowing can University Cooperative Extension, adjacent Oregon. prevent seed production F. L. Poston, Director; Oregon and eventually weaken State University Extension BIOLOGY AND plants. Clean cultivation in Service, 0. E. Smith, Director; ECOLOGY cropland will effectively University of Idaho Cooperative control this weed. Extension System, LeRoy D. Luft, Director; and the U. S. Wild four o'clock is a According to reports from perennial that reproduces Department of Agriculture in the Midwest, 1 or 2 years of furtherance of the Acts of May 8 and spreads by seed. clean cultivated crops will and June 30, 1914. Cooperative Flowering begins in May, practically eliminate the Extension programs and policies and the plant may produce heaviest infestations. For comply with federal and state ripe seeds by mid-June. The chemical control laws and regulations on nondiscrimination regarding race, little "umbrellas" formed by recommendations, refer to the bracts surrounding the color, national origin, religion, the Pacific Northwest Weed gender, age, disability, and seeds hitch rides on Control Handbook, an gender preference. Published vehicles, especially the front annually revised Extension June 1991. 50/0/50 bumper and radiator. publication available from PNW363

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