Oenothera triloba
Oenothera organensis
stemless evening-primrose
Organ Mountain evening primrose
(when present) ascending, 1–several, densely leafy, 0–20 cm.
weakly erect to ascending, many from base, forming clumps 1–1.5 m diam., often branched distally, 30–60 cm.
in a basal rosette, sometimes also cauline, (2.5–)6–25(–32) × (0.6–)1.5–4(–5) cm, thin;
petiole (0.5–)1–8 cm;
blade oblanceolate to elliptic, margins irregularly pinnatifid, sometimes subentire, apex acute to obtuse or rounded.
in a weakly developed basal rosette and cauline, basal 9–23 × 1–2.5 cm, cauline 5–11 × 1.5–3.5 cm;
petiole 0.5–1.5 cm;
blade very narrowly oblanceolate to narrowly elliptic, margins undulate, remotely and bluntly dentate.
1–4 opening per day near sunset, without noticeable scent;
buds with subequal free tips 2–7 mm;
floral tube (20–)28–95(–138) mm;
sepals (6–)10–30(–35) mm;
petals pale yellow, fading pale orange, drying lavender, (10–)12–30(–38) mm;
filaments (5–)8–15(–18) mm, anthers (3.5–)4–11 mm;
style (3.4–)4.2–11.5(–16.3) mm, stigma usually surrounded by anthers, sometimes (especially in some Texas populations) exserted beyond anthers.
opening near sunset, not strongly scented;
buds with free tips terminal, erect, 3–10 mm;
floral tube straight, 100–165(–190) mm;
sepals 25–50 mm;
petals yellow, fading deep reddish orange, broadly obovate with truncate apex, or obcordate, 30–55 mm;
filaments 18–35 mm, anthers 10–19 mm;
style 140–235 mm, stigma exserted beyond anthers at anthesis.
woody in age, rhombic-obovoid, winged, wings broadly triangular, 5–10 mm wide, often terminating in a hooked tooth, (10–)15–25(–28) × 4–8 mm (excluding wings), valve surface reticulate, dehiscent 1/8–1/3 their length.
erect to slightly spreading at acute angle from stem, cylindrical, 25–35 ×4–5.5 mm, dehiscent at least 3/4 their length.
asymmetrically cuneiform, (2.1–)2.5–3(–3.3) mm.
numerous, in 2 distinct rows per locule, dark reddish brown, sometimes with darker flecks, obovoid, asymmetrical, irregularly angled, 1.5–2.1 × 1–1.2 mm, surface irregularly pitted and with collapsed papillae.
= 14.
= 14.
Oenothera triloba
Oenothera organensis
Oenotheratriloba is primarily a species of the high plains from eastern Socorro County, New Mexico, east through all but eastern Texas, Oklahoma, to southern Kansas, east of Meade and Pawnee counties and south of Douglas and Saline counties. It becomes more sporadic eastward into Missouri south of the Missouri River, northwestern and north-central Arkansas, central and eastern Tennessee, northern Alabama, and Logan and Warren counties, Kentucky; also known from disjunct sites in northern Mexico from Nuevo León, Chihuahua, and Baja California, Mexico; and, introduced in Illinois, Indiana, Ohio, Kentucky (Campbell and Fayette counties), Pennsylvania, Virginia, Maryland, and the District of Columbia. Areas where it was introduced are represented by old collections; no current information indicates their continued presence in any of these areas. It was recently collected in Baca County, Colorado.
Capsules of dead plants sometimes form pineconelike clusters of ten to 100 or more capsules.
The illegitimate names Lavauxia nuttalliana Spach and L. triloba (Nuttall) Spach var. watsonii Britton pertain here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Oenothera organensis is known only from the Organ Mountains, Doña Ana County, especially on the east side. Various studies have been done to assess the status of this narrow endemic and estimate 2000 to 5000 individuals with wide fluctuations likely due to variation in rainfall (W. Dietrich et al. 1985). Oenothera organensis could decline if degradation of habitat increases in the Organ Mountains. The genetics and population biology of this taxon have been heavily studied in the past (summarized in Dietrich et al.). It is self-incompatible.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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