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.
Hybridizes with :
- Creeping Yellow-Cress (Rorippa sylvestris) to produce
Hybrid Yellow-cress (Rorippa × anceps ) The most number of the hybrids being found in just ~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 the extent that it back-crosses 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 birthday when the second set of these photos was 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 :
|