Sisymbrium loeselii L.

Tall Hedge Mustard

© SRTurner

Family - Brassicaceae

Habit - Annual forb.

Stem - Strongly ascending to erect, to 1.5 m, usually hairy, sometimes nearly glabrous toward tip.

	Stem and upper leaves.
© SRTurner

Leaves - Basal and alternate, short-petiolate, not clasping, lanceolate to triangular in outline, 2-15 cm long, pinnately lobed or divided into 3-9 lobes, these entire to toothed or lobed. Lowermost leaves hairy, uppermost sparsely hairy to glabrous.

	Basal leaves.
© SRTurner

	Leaf abaxial surface.
© SRTurner

	Upper and lower leaves.
© DETenaglia

Inflorescences - Panicles or racemes at branch tips, the flowers not subtended by bracts.

	Inflorescence.
© SRTurner

Flowers - Sepals 3-4 mm long, linear-lanceolate to narrowly oblong, erect or ascending, green. Petals 6-8 mm long, not lobed, yellow. Stamens 6. Styles 0.5-0.7 mm long at fruiting.

	Flowers.
© SRTurner

	Calyx.
© SRTurner

	Corollas.
© SRTurner

Fruits - Siliques 2.0-3.5 cm long, spreading or ascending at maturity, not appressed to the inflorescence axis, the stalk slender, noticeably narrower than the fruit. Seeds 40-60 per fruit, 0.7-1.0 mm long.

Flowering - May - October.

Habitat - Levees, crop field margins, pastures, railroads, open disturbed areas.

Origin - Native to Eurasia.

Lookalikes - S. altissimum, S. officinale. More broadly, several other mustards such as Barbarea vulgaris and Brassica spp.

Other info. - This tall, gangly, introduced mustard is not particularly common in Missouri. It was first reported in the state in 1954 and has become more common since then, but is still largely restricted to railroads and agricultural fields. Most of its statewide distribution is from counties bordering the Missouri River, and the majority of those counties have reported the plant. Its broader distribution is widely scattered in the northern half of the continental U.S., ranging into Canada.

Many mustards look similar and can present challenges to confident identification. Sisymbrium loeselii is characterized by its tall, sparse habit, large-ish flowers, and petiolate, irregularly pinnatifid leaves. Relative to most mustards, this plant has an abnormally long flowering time, which begins in mid-spring and sometimes lasts until frost or beyond. Some of the flower pictures shown above were taken in November.

Photographs taken off Route 118, Holt County, MO., 5-3-00 (DETenaglia); also along the Katy Trail near Augusta, St. Charles County, MO, 5-4-2011, and along the Katy Trail near Dutzow, Warren County, MO, 7-4-2014, 11-5-2019, and 4-22-2020 (SRTurner).