Rorippa

Scientific name

Rorippa Scop. (including Nasturtium W.T.Aiton)

Common names

yellow cress, water cress

Family

Brassicaceae

Similar genera

Cardamine, Lysimachia

Native distribution

cosmopolitan, mostly through introductions

Species cultivated

Rorippa nasturtium-aquaticum (L.) Hayek [synonym of Nasturtium officinale R. Br.]

Rorippa aquatica (Eaton) E.J. Palmer & Steyerm. [also offered under the synonym Aromracia aquatica (Eaton) Wiegand; both synonyms of Neobeckia aquatica (Eaton) Greene]

Adventive distribution

Numerous Rorippa species have been introduced on most continents, particularly in temperatetemperate:
(adj) of the climatic zone between boreal and tropical
regions; Rorippa nasturtium-aquaticum is widely distributed and has become almost cosmopolitancosmopolitan:
(adj) essentially worldwide in distribution
.

Weed status

Rorippa are noxious weeds around the world. Most of these are not exclusively aquatic, but tolerate periodic inundation. Rorippa nasturtium-aquaticum is a common weed of irrigation canals and natural waterways but is rarely problematic.

Habit

emergent emergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
herb with erect inflorescence

Brief description

Annual or perennialperennial:
(adj) (of a plant) having a life cycle of more than two years
. Stems compact to erect and ascending, sometimes floating or creeping. Leaves in a basalbasal:
(adj) at or pertaining to the base, or point of attachment
rosette or caulinecauline:
(adj) pertaining to or belonging to the stem
, alternatealternate:
(adj) (of leaves) bearing one leaf per node; placed singly on the stem at different heights
, simple or pinnatepinnate:
(adj) in the form of a feather; of, e.g., leaflets, lobes, or veins: arranged in two rows along an axis
, often conspicuously emarginateemarginate:
(adj) with a shallow notch at apex
and undulateundulate:
(adj) (of, e.g., a margin) with a wavy surface; wavy in the vertical (up and down) plane
. Inflorescenceinflorescence:
(n) the arrangement of flowers on the floral axis
a simple or branched racemeraceme:
(n) an indeterminate, unbranched inflorescence having pedicelled flowers on a usually elongated axis (may be cymose)
. Flowers zygomorphiczygomorphic:
(adj) bilaterally symmetrical; symmetrical along only one plane
; sepals 4; petals 4, white, yellow or blue. Dispersal by seeds or vegetativevegetative:
(adj) (1) pertaining to or to the growth of plant organs or plant parts that have nonreproductive functions, such as leaves, roots, stems, etc.; (2) concering non sexual propagules such as tubers, turions, stem fragments, root crowns, rhizomes
fragments.

Natural habitat

riparian, shallow streams, littorallittoral:
(adj) of or along the shore
zone, mostly in flooded areas; rarely tolerates extended submersion

Additional comments

Some taxonomists consider the genus Rorippa to exclude Nasturtium. Here Rorippa includes Nasturtium, Neobeckia (a monotypicmonotypic:
(adj) represented by a single example (species)
genus), and Armoracia aquatica (Eat.) Wieg. (=Rorippa aquatica). R. nasturtium-aquaticum (water cress) is commonly used as a vegetable in many countries. This has led to its wide-ranging introduction in many countries through deliberate plantings in natural waterways. Some authorities prefer the name Nasturtium officinale; both names are in equal usage in the literature.