Hibiscus trionum L.
Family: Malvaceae
flower of an hour,  more...
[Trionum trionum (L.) Woot. & Standl.]
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Plant: annual herb; 0.5 m tall, the stems sparsely stellate-pubescent to glabrate Leaves: deeply 3-parted, each lobe pinnately divided, very sparsely pubescent, 3-5 cm long Flowers: axillary, the pedicels 1-3 cm long; bracts of involucel 4-7 mm long; calyx 15-20 mm long, inflated and membranous with dark-pigmented veins; petals 2-2.5 cm long, yellow with a prominent purple spot at base Fruit: FRUITS ovoid capsules, included in calyx, hispid; SEEDS 2 mm long, warty Misc: Cultivated plant, doubtfully established; ca. 2150 m (7000 ft); Aug REFERENCES: Fryxell, Paul A. 1994. Malvaceae. J. Ariz. - Nev. Acad. Sci. Volume 27(2), 222-236.
Annual herb 30 - 50 cm tall Stem: ascending, slender, branching, and hairy. Leaves: alternate, long- stalked, hairy, deeply three parted (nearly to base) with segments fairly narrow, oblong or egg-shaped, and very coarsely toothed. Flowers: axillary, stalked, ephemeral, pale yellow with purple center, relatively small (3 - 8 cm diameter), with five spreading petals, and five sepals, which are immediately subtended by more than ten, slender, linear bristly bractlets. Sepals: five, but fused for over half their length, then separating into five widely-triangular lobes, which enlarge in fruit to enclose the capsule. The calyx as a whole has very conspicuous veins, which have swollen-based, spreading, stiff, straight hairs along their length. Petals: five, pale yellow with purple base, 1.5 - 4 cm long, widely spreading, narrowest at base and widening to shallowly toothed to slightly wavy tips. The petals are expanded for only a few hours. Stamens: numerous, but filaments fused into a long tube, with separate anthers all along the tube sides, and five teeth at top of the tube. Pistil: enclosed by the stamen tube, with one five-chambered superior ovary, five fused styles coming up through center of stamen tube and extending beyond it before branching above into five, obvious, rounded stigmas. Fruit: long-stalked, five-chambered, many-seeded, stiff bristly-hairy, somewhat rounded capsules enclosed by the persistent, greatly inflated, five-angled calyx. Each capsule chamber contains several, finely warty seeds, which are released as the top of the capsule opens outward and lengthwise downward.

Similar species: Hibiscus trionum is unlike our other species in this genus since it is an annual with ephemeral flowers that are only fully open for a few hours, the flowers are pale yellow and relatively small with spreading petals, and the leaves are very deeply three-lobed with the narrow lobes coarsely toothed.

Flowering: June to October

Habitat and ecology: A common weed of cultivated ground, found in gardens, cornfields, and similar habitats.

Occurence in the Chicago region: non-native

Notes: This plant is native to southern Europe and is a common weed in North America.

Author: The Field Museum

Branching, hairy annual 3-5 dm; lvs long-petioled, deeply 3-parted, the segments oblong to obovate, coarsely serrate or lobed; cal conspicuously veined, hispid on the nerves with spreading simple hairs from swollen bases; pet 1.5-4 cm, pale yellow with purple base, expanded only a few hours; mature cal inflated, 5-angled, enclosing the hirsute fr; seeds finely verrucose; 2n=28, 56. Native of s. Europe; fields, roadsides, and waste places from N.S. to Minn., s. to Fla. and Tex. July-Sept.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.
From Flora of Indiana (1940) by Charles C. Deam
An obnoxious weed in rather sandy soil in cultivated grounds in many parts of the state, especially in the glaciated area. I can recall the time when I rarely saw it but now in certain areas it forms a complete stand in cornfields. Although it is an annual, when once established, it is difficult to exterminate on account of its numerous seeds and their unusual viability.
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Richard J. Shaw  
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