GREAT YELLOW-CRESS

Rorippa amphibia

Cabbage Family [Brassicaceae]

month8may month8jun month8june month8jul month8july month8aug month8sep month8sept

status
statusZnative
flower
flower8yellow
morph
morph8actino
petals
petalsZ4
type
typeZspiked
stem
stem8round
stem
stem8ribbed

17th Aug 2007, Whatstandwell, Cromford Canal. Photo: © RWD
An aquatic plant of shallow fresh-water.


17th Aug 2007, Whatstandwell, Cromford Canal. Photo: © RWD
Lower stem leaves crinkly, coarsely-toothed and often with shallow lobes (pinnatisect) nearer the base.


17th Aug 2007, Whatstandwell, Cromford Canal. Photo: © RWD
These early lobed leaves do not persist and are replaced by simple leaves as the plant grows taller. (Austrian Yellow-cress lacks the lobes on early leaves).


17th Aug 2007, Whatstandwell, Cromford Canal. Photo: © RWD
Typically a submerged rhizhome (which is white) curves upwards out of the water.


17th Aug 2007, Whatstandwell, Cromford Canal. Photo: © RWD
Can reach as high as 1.2m, but typically anywhere between 40cm and 120cm high. This one flowering near top.


24th June 2006, Narrow Boat Trip. Photo: © RWD
Older specimens were found on another canal. Here the pinnatisect leaves have been replaced by simpler leaves. Stem often wavy.


24th June 2006, Narrow Boat Trip. Photo: © RWD
Leaves are highly variable anyway. Upper stem leaves (toothed or not) are oblong-lanceolate and often acute at the end. Flowers seem to droop somewhat like little yellow bells.


24th June 2006, Narrow Boat Trip. Photo: © RWD
Flowers are small, bell-shaped, with 4 very short petals sticking out perpendicular to the stalk. Stalks long in relation to the flower length.


17th Aug 2007, Whatstandwell, Cromford Canal. Photo: © RWD
A profusion of flowering stems.


24th June 2006, Narrow Boat Trip. Photo: © RWD
The leaves are winged on their stalks and join the stem in a flat butt-joint (un-like those of Austrian Yellow-cress which have very short auricles each side of the main stem).


24th June 2006, Narrow Boat Trip. Photo: © RWD
Winged leaf petioles. Prominent mid-rib.


24th June 2006, Narrow Boat Trip. Photo: © RWD
The non-auricled butt-joint of the winged leaves to the main stem. Stems round with ridges.


Easily mistaken for : Austrian Yellow-cress (Rorippa austriaca) is very similar but the early leaves lack any lobes and has smaller seed pods with a long beak, it has white rhizomes as does Great Yellow-cress. 0

Hybridizes with :

  • Creeping Yellow-Cress (Rorippa sylvestris) to produce Hybrid Yellow-cress (Rorippa × anceps) The most body of the hybrids, being found in just about 20 hectads. Unlike Great Yellow-cress it has deeply-lobed upper stem leaves (simple in Great Yellow-cress). This hybrid is fertile and variable to it back-crossing with either of its parents.
  • Marsh Yellow-cress (Rorippa paluatris) to produce Yellow-cress (Rorippa × erythrocaulis) which has only ever been seen in a dozen hectads at most. Unlike Great Yellow-cress it has pinnatifid (deeply lobed) leaves.
  • Austrian Yellow-cress (Rorippa austriaca) to produce Rorippa × hungarica which has only ever been spotted in two hectads, none anywhere near where the photos were taken. Unlike Great Yellow-cress it has acutely-toothed leaves with conspicuous auricles clasping the stem.
There are other small differences too between these hybrids.

The photos from the Cromford canal are definitely of R. amphibia, but it is not known if those from the Narrow Boat Trip are since your Author cannot remember exactly where he was on his 60th when the second set of these photos were taken.

Great Yellow-cress is now found only in (roughly) the Southern part of the UK. It is an aquatic plant which frequently hybridizes with Creeping Yellow-Cress (Rorippa sylvestris) and can be present with one or the other parent absent.

The seed pods of Great Yellow-cress have a long petiole before reaching the ovoidal pod which has the short style still attached (which is shorter than that of Austrian Yellow-cress)

Uniquely identifiable characteristics

Distinguishing Feature :


  Rorippa amphibia  ⇐ Global Aspect ⇒ Brassicaceae  

Distribution
 family8Cabbage family8Brassicaceae

 BSBI maps
genus8Rorippa
Rorippa
(Yellow-Cresses)

GREAT YELLOW-CRESS

Rorippa amphibia

Cabbage Family [Brassicaceae]