Northern Prairie Wildlife Research Center
Aquatic and Wetland Vascular Plants of the Northern Great Plains
22. Brassicaceae, the Mustard Family
3. Nasturtium R. Br. -- Watercress
1. Nasturtium officinale R. Br.
Glabrous, fibrous-rooted, perennial aquatic; stems rather lax and trailing
in water or on mud, freely rooting from lower nodes, erect or ascending toward
the tips, 1-5 dm long. Leaves 4-13 cm long including the short to long
petiole, 2-5 cm wide, pinnate or sometimes the earliest ones simple with only
the terminal leaflet present; terminal leaflet ovate-cordate to subrotund or
obovate, often much larger than the elliptic to obovate lateral leaflets, entire
or weakly crenate. Racemes 1-several per stem, flat-topped and elongating
in fruit. Sepals greenish-white, oblong, the outer pair saccate at the
base, 1.5-2.5 mm long; petals white, sometimes tinged with purple, obovate,
3.5-5 mm long. Siliques linear, often curved, 10-25 mm long, ca. 2 mm
thick, subterete, tipped with a short, truncate style beak 1 mm or less long;
seeds in 2 rows in each cell of the fruit, conspicuously areolate. Jun--Oct.
Springs and streams where water is fresh; e and sw SD and NE, especially common
in streams of the Black Hills; (Intro. from Eurasia and established throughout
most of the U.S. and s Can.). Rorippa nasturtium-aquaticum (L.) Hayek.
This plant is the watercress of commerce and is often used as a salad green.
Previous Species -- Cardamine pensylvanica Muhl.
ex Willd. -- Bitter Cress
Return to Family -- Brassicaceae -
The Mustard Family
Next Species -- Rorippa austriaca (Crantz) Bess.
-- Austrian field cress