Sisymbrium

1. Fruit (0.7–) 1–1.4 (–1.8) cm long, on pedicels less than 4 mm long, even when young closely appressed to axis of inflorescence; seeds 10–20 per fruit.

S. officinale

1. Fruit (2–) 3–8 (–10) cm long, on pedicels at least 6 mm long, spreading; seeds 40–120 per fruit.

2. Fruiting pedicel as thick as fruit; uppermost leaves pinnatisect into narrowly linear to filiform lobes to 2 mm wide.

S. altissimum

2. Fruiting pedicel narrower than fruit; uppermost leaves entire or pinnately lobed but with wider segments.

3. Petals 2–3.5 (–5) mm long; flowers and buds overtopped by ends of uppermost young fruit.

S. irio

3. Petals 6–8 mm long; flowers and buds barely if at all surpassed by tips of fruit.

S. loeselii

All species found in Sisymbrium

Sisymbrium altissimumTUMBLE MUSTARD 
Sisymbrium irioLONDON ROCKET 
Sisymbrium loeseliiTALL HEDGE MUSTARD 
Sisymbrium officinaleHEDGE MUSTARD 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. June 28, 2017. http://michiganflora.net/genus.aspx?id=Sisymbrium.