Lepidium oblongum Small

Stinking Pepperweed


CC = *
CW = 5
MOC = 6

© SRTurner

Family - Brassicaceae

Habit - Annual forb.

Stem - Ascending to erect, to 30 cm, often branched, pubescent with papillate hairs.

Lepidium_oblongum_basals.jpg Basal rosettes.

© SRTurner

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.

Lepidium_oblongum_leaf1.jpg Lower leaf, adaxial.

© SRTurner

Lepidium_oblongum_stem.jpg Stem and upper leaves.

© SRTurner

Inflorescences - Elongate racemes, the rachis with papillate hairs, bracts absent.

Lepidium_oblongum_inflorescence.jpg Inflorescences.

© SRTurner

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.

Lepidium_oblongum_flowers.jpg Flowers.

© SRTurner

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.

Lepidium_oblongum_fruits.jpg Fruits.

© SRTurner

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. Since the initial report, the plant has been found in several other counties, always in highly disturbed spots. Beyond Missouri, the plant occurs mostly in states to the south and west. Although it is native in most parts of the U.S., populations in Missouri are considered introduced.

The plant is easy to recognize, with inflorescences characteristic of the pepperweeds and leaves which are pinnately lobed. 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. 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, in West Alton, St. Charles County, MO, 4-29-2016, and along the Katy Trail near Treloar, Warren County, MO, 5-2-2020 (SRTurner).