Oenothera macrocarpa
Oenothera biennis
bigfruit evening primrose, Missouri evening primrose, Ozark sundrop
common evening-primrose, eastern evening primrose, evening star, King's-cureall, small flower evening primrose
moderately leafy, (1–)4–40(–60) cm.
erect, green or flushed with red on proximal parts, sometimes inflorescence axis red, unbranched or with side branches obliquely arising from rosette or stem, 30–200 cm.
cauline, (2.8–)3.7–12.5(–17) × (0.1–)0.4–3(–4.5) cm;
petiole (0.4–)1–4(–6) cm;
blade linear, lanceolate-elliptic, elliptic to oblanceolate or suborbiculate, margins entire or conspicuously or inconspicuously denticulate or serrulate, sometimes undulate, apex usually acute, sometimes obtuse or retuse (subsp. incana).
in a basal rosette and cauline, basal 10–30 × 2–5 cm, cauline 5–22 ×(1–)1.5–5(–6) cm;
blade usually green to pale green, narrowly oblanceolate to oblanceolate, sometimes narrowly elliptic to elliptic distally, margins usually flat, rarely undulate, bluntly dentate, teeth widely spaced, sometimes sinuate-dentate proximally or lobed;
bracts persistent.
erect, unbranched or with secondary branches just proximal to main one, internodes in fruit usually shorter than capsule.
usually 1 or 2, rarely more, opening per day near sunset, fading next morning, sometimes (subspp.
opening near sunset;
buds erect, 3.5–6 mm diam., with free tips terminal, erect or spreading, 1.5–3 mm;
floral tube (20–)25–40 mm;
sepals yellowish green, rarely flushed with red or red-striped, 12–22(–28) mm;
petals yellow to pale yellow, fading yellowish white and somewhat translucent, very broadly obcordate, 12–25(–30) mm;
filaments 8–15(–20) mm, anthers 3–6(–9) mm, pollen 50% fertile;
style 30–55 mm, stigma surrounded by anthers at anthesis.
papery in age, narrowly ellipsoid to lanceoloid, sometimes twisted (subsp. fremontii), winged, wings (2–)10–28(–34) mm wide, body (13–)25–70(–115) × 2–9 mm, dehiscent 1/4–1/3 their length;
pedicel 1–12(–25) mm.
erect or slightly spreading, dull green when dry, lanceoloid, 20–40 × 4–6 mm, free tips of valves 0.8–1.5 mm.
numerous, rarely as few as 8, in 1 row per locule, obovoid, (2–)3–5 × 1–2.3 mm.
1–1.2 × 0.6–1.1 mm.
and oklahomensis) lasting for 2 days, weakly scented;
buds with unequal free tips 1–11(–15) mm;
floral tube (21–)35–140(–160) mm;
sepals (20–)25–65(–75) mm;
petals bright yellow, fading orange, reddish orange or mostly unchanged, obovate to very broadly obovate, (17–)25–65(–68) mm, usually with terminal notch and/or tooth, margin sometimes erose;
filaments 13–40(–44) mm, anthers 10–24(–25) mm;
style (45–)55–192 mm, stigma usually exserted beyond anthers at anthesis.
= 14.
Oenothera macrocarpa
Oenothera biennis
Subspecies 5 (4 in the flora).
Oenotheramacrocarpa is variable and has differentiated extensively in the Great Plains region. Each of the five distinctive subspecies occupies a different geographical and ecological situation. Only subsp. mexicana W. L. Wagner from Coahuila, Mexico, occurs outside of the flora area. In general, the subspecies are sharply distinct and each is characterized by a number of features, including pubescence, leaf features, flower and floral tube size, and size and morphology of the capsules and seeds. The five entities are treated as subspecies primarily because of their complete interfertility and extensive intergradation in any area of marginal contact. Intermediates are known between subsp. macrocarpa and subspp. fremontii and oklahomensis and between subspp. incana and oklahomensis. There is also some evidence that suggests past hybridization between subspp. fremontii and incana although there is no present contact between them. All subspecies are self-incompatible.
Oenothera alata Nuttall (1818) is an illegitimate name based on O. macrocarpa and pertains here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Oenothera biennis is a PTH species and usually forms a ring of 14 chromosomes or a ring of 12 and 1 bivalent in meiosis, and is self-compatible and autogamous (W. Dietrich et al. 1997). It has plastome II and a BA or AB genome composition across different populations.
W. Dietrich et al. (1997) found that in the western half of the United States, where Oenothera biennis is most likely introduced, there are distinctive series of forms that seemed similar to a phenotype of O. biennis that originated in Europe. The most distinctive morphological characters of this western form are the densely villous stems with pustulate hairs and the intense, often dark red color of the stems and sepals, characters which are not typical for the eastern North America forms of O. biennis. The pustulate pubescence of this form is also a characteristic feature of many O. elata and O. villosa subsp. strigosa forms, suggesting possible past hybridization with them. Crossing studies confirm that one of these taxa was most likely involved, and these studies showed that, like O. biennis, they are all AB and BA genomic combinations. One of the seemingly odd features of this form is its scattered distribution across a wide expanse of western states. A possible explanation is that perhaps O. biennis spread westward during glacial periods, hybridized with AA taxa (O. elata and O. villosa subsp. strigosa), followed by compression during warming periods since. A hypothesis of repeated recent hybridization does not seem likely since more typical eastern forms of O. biennis are not present throughout much of the western states. Oenothera biennis hybridizes with the other species of subsect. Oenothera with which it comes in contact, includingO. grandiflora, O. nutans, O. oakesiana, O. parviflora, O. villosa subsp. strigosa, and O. villosa subsp. villosa.
Oenothera biennis subsp. rubricaulis (Klebahn) Stomps is a later homonym that pertains here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Herbs glabrous. | → 2 |
2. Leaf blades usually very broadly elliptic to suborbiculate, rarely oblanceolate or elliptic, 2–4.3 cm wide, margins usually entire, sometimes inconspicuously denticulate, usually flat, sometimes undulate. | subsp. incana |
2. Leaf blades usually elliptic to lanceolate-elliptic, sometimes linear, (0.3–)0.8–2(–3) cm wide, margins usually conspicuously denticulate to serrulate, rarely subentire, usually undulate. | subsp. oklahomensis |
1. Herbs strigillose. | → 3 |
3. Bud free tips 1–2(–5) mm; petals (17–)25–33(–37) mm; floral tubes (21–)35–65(–80) mm; capsules often twisted, 13–30(–65) mm, wings 2–5(–9) mm wide. | subsp. fremontii |
3. Bud free tips (4–)5–11(–12) mm; petals (25–)31–65(–68) mm; floral tubes (50–)70–140(–160) mm; capsules not twisted, (28–)30–70(–115) mm, wings 10–28(–34) mm wide. | → 4 |
4. Leaves green or younger ones grayish green, moderately strigillose, rarely more densely strigillose, blades often lanceolate-elliptic to broadly elliptic, sometimes linear or lanceolate, 0.4–2.3(–3) cm wide; capsule wings (14–)18–28(–34) mm wide. | subsp. macrocarpa |
4. Leaves gray, densely strigillose, blades very broadly elliptic to suborbiculate, rarely oblanceolate or elliptic, 2–4.3 cm wide; capsule wings 10–15(–24) mm wide. | subsp. incana |
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