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