Lepidium oblongum Small
Family - Brassicaceae
Habit - Annual forb.
Stem - Ascending to erect, to 30 cm, often branched, pubescent with papillate hairs.
Stem and upper leaves.
Leaves - Basal and alternate. Basal and lowermost stem leaves 3.0-7.0 cm long, 2 or 3 times pinnately divided with oblong divisions. Upper stem leaves 1.0-2.0 cm long, pinnatifid or laciniate, oblanceolate to linear, sessile, the bases not auriculate, sparsely pubescent.
Lower leaf, adaxial.
Inflorescences - Elongate racemes, the rachis with papillate hairs, bracts absent.
Flowers - Sepals 4, 0.7-1.0 mm long, oblong. Petals absent or present and 0.1-0.7 mm long, white. Stamens 2. Styles to 0.1 mm long.
Fruits - Silicles 2.2-3.5 mm long, nearly circular, widest at the middle, the tip shallowly notched and relatively narrowly winged, flattened, glabrous, the stalks pubescent all around. Seeds 1.2-1.6 mm long, ovate, not winged, the surface with a minute, netlike pattern, brown.
Flowering - April - May.
Habitat - Open disturbed areas.
Origin - Native to the U.S.
Lookalikes - Other members of the genus.
Other info. - This weedy species was first collected in Missouri by James Sullivan, in 2002,
at a truck stop. It was initially determined as L. ruderale, an Old World species which has been found in scattered locations
in the U.S. The specimen was later redetermined as L. oblongum Small by Brassicaceae expert Ihsan Al-Shehbaz.
Lepidium oblongum differs from the morphologically similar L. ruderale in having
even the upper leaves moderately to deeply divided (vs. entire or toothed), the sepals more or less persistent at fruiting
(vs.shed early), and in its tendency toward broadly obovate to circular (vs. mostly elliptic) fruits. Although the plant is native in parts of
the U.S., populations in Missouri are considered introduced.
Since the intial report in 2002, the plant has been found in several other counties, always in highly disturbed spots. The plant is
easy to recognize, with inflorescences characteristic of the pepperweeds and leaves which are pinnately lobed. It is possible that L. ruderale
will also appear in Missouri at some point, and this should be considered when making determinations.
Since the intial report in 2002, the plant has been found in several other counties, always in highly disturbed spots. The plant is easy to recognize, with inflorescences characteristic of the pepperweeds and leaves which are pinnately lobed. It is possible that L. ruderale will also appear in Missouri at some point, and this should be considered when making determinations.
Photographs taken at the Dutzow Katy Trailhead, Warren County, MO, 5-7-2013, and in West Alton, St. Charles County, MO, 4-29-2016 (SRTurner).