Oenothera filiformis (Small) W.L. Wagner & Hoch

Large-Flowered Gaura

Oenothera filiformis plant

© SRTurner

Family - Onagraceae

Habit - Annual or rarely biennial forb, with fleshy taproot.

Stem - Arched or ascending to erect, 1 to several from base, to 2 m, usually many-branched well above the base, moderately to densely pubescent with a mixture of appressed to upward-curved, somewhat woolly nonglandular hairs and short glandular hairs, sometimes also with scattered longer, spreading to loosely upward-curved hairs.

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Stem.
© DETenaglia

Leaves - Basal and alternate, simple. Rosette leaves usually withered at flowering, often highly irregular in outline, the margins entire to wavy or with irregular teeth or shallow lobes, the surfaces glabrous or with short, appressed hairs, the undersurface often also with slightly longer hairs along the midvein. Stem leaves often with axillary leaf fascicles, 1.5-13 cm long, 2-28 mm wide, narrowly lanceolate to elliptic, the margins entire to wavy or with broadly spaced, irregular teeth or shallow lobes, the surfaces glabrous or with short, appressed to curved hairs, the undersurface often also with slightly longer hairs along the midvein, the secondary veins of at least the larger blades usually relatively conspicuous.

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Stem and leaves.
© SRTurner

Inflorescences - Well-branched panicles of open to moderately dense, often wandlike spikes, often half or more of the total length of the plant, the axes usually densely and minutely glandular- and/or glandular-hairy. Bracts relatively inconspicuous, 1-6 mm long, 0.5-2.0 mm wide, narrowly lanceolate to ovate.

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Inflorescence.
© SRTurner

Flowers - Strongly zygomorphic, with all of the petals positioned in the upper half of the flower, opening at dusk, the floral tube 4-13 mm long, short-hairy. Sepals 7-18 mm long, short-hairy, lacking free tips in bud. Petals 6.5-15.0 mm long, 2-7 mm wide, elliptic-oblanceolate, tapered abruptly to a pronounced stalklike base, white, fading to pink or red. Stamens with the filaments 5-13 mm long, spreading to pendant, glabrous at the base, the anthers 1.5-5.0 mm long, brownish red. Style 12-34 mm long, the stigma positioned well beyond the anthers, deeply 4-lobed, the lobes 0.5-1.5 mm long.

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Calyx and ovary.
© SRTurner

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Flowers.
© SRTurner

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© SRTurner

Fruits - Indehiscent capsules, appearing mostly 1-locular, 4.5-7.0 mm long, 1.5-2.5 mm in diameter, the body ellipsoid, 4-angled throughout, not constricted to a stalklike base but sometimes tapered to a short, thick, cylindric base. Seeds 2-4 per fruit, not in definite rows, 1.2-3.0 mm long, 1.5-2.5 mm wide, ovoid, sometimes irregularly flattened (by crowding in fruit), the surface yellowish brown to reddish brown, smooth.

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Fruits.
© SRTurner

Flowering - June - October.

Habitat - Glades, prairies, forest openings, streambanks, fields, open disturbed areas.

Origin - Native to the U.S.

Lookalikes - Certain other members of the Gaura division; e.g. O. gaura, O. curtiflora, and O. suffrutescens.

Other info. - This shrublike species is common across most or all of Missouri. Its main North American range comprises a band stretching from Iowa down to the Gulf Coast. It is somewhat weedy and indiscriminate in its habitat requirements.

This species was long known as Gaura longiflora. Differentiation from other members of the Gaura section rests on sepal length, pubescence characters, and details of the fruits. Oenothera tends to be a challenging genus, with detailed examination of both flowers and fruits necessary for rigorous keying.

Photographs taken along the shores of the Current River, Shannon County, MO., 9-20-03 (DETenaglia); also at Shaw Nature Reserve, Franklin County, MO, 09-02-2006, Busch Wildlife Area, St. Charles County, MO, 08-30-2008, St. Joe State Park, St. Francois County, MO, 09-10-2012, Johnson's Shut-Ins State Park, Reynolds County, MO, 08-20-2013, and Onondaga Cave State Park, Crawford County, MO, 09-11-2017, (SRTurner).



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