Oenothera linifolia Nutt.
Threadleaf Evening Primrose
Family - Onograceae
Stems - To +/-30cm tall, erect, herbaceous, simple to branching near apex, from a branched taproot, multiple from base, hirsutulous below, glabrous near apex.
Leaves - Alternate. Basal rosette typically drying by anthesis. Leaves of rosette petiolate, spatulate, to 3cm long, 6mm broad, entire to shallow serrate, glabrous. Cauline leaves linear, 2-3cm long, 1-2mm broad, glabrous, entire.
Inflorescence - Terminal raceme, compact in flower, elongating in fruit. Each flower subtended by a single bract. Bracts acute to acuminate, lance-ovate, mostly glabrous, entire but with strigose margins. Flowers sessile.
Flowers - Petals 4, yellow, distinct, obcordate, 5mm long, 4-5mm broad, glabrous. Stamens 8, erect, adnate at apex of floral tube. Filaments yellow, glabrous, +/-2mm long. Anthers reddish-yellow, .7mm long. Style yellowish, glabrous, 4.5mm long. Stigma 4(5)-lobed. Ovary inferior, 4-locular, 4-angled, slightly winged on angles, obovoid in outline, 5-6mm long n flower, longer in fruit, with antrorse strigose pubescence. Placentation axile. Ovules many. Floral tube yellow, 3mm long, mostly glabrous or with a few strigose hairs as ovary. Sepals 2, reflexed, ovate, glabrous internally, with small strigose hairs externally, yellow-green, -3mm long, 2.3mm broad.
Flowering - April - July.
Habitat - Glades, rocky fields.
Origin - Native to U.S.
Other info. - This small species can be found in the southern half of Missouri. The small flowers of this species wilt quickly and barely last a day. More commonly, the plant is found in fruit, if at all. Because of its thin stems and leaves, and its small flowers, this species is often overlooked.
Photographs taken at Dave Rock Conservation Area, St. Clair County, MO., 6-16-05, and on Taum Sauk Mountain, MO., 6-1-03.