Rare Plant Profile – Blunt-leaved Watercress (Rorippa curvipes Greene)
Blunt-leaved watercress (Rorippa curvipes Greene) is an annual or occasionally biennial herb in the Mustard Family (Brassicaceae [Cruciferae]). Its short, slender stems, which grow from a taproot, are usually branched, ascending, decumbent, prostrate, or rarely erect, and range in length between 10-50 cm. Leaves of this plant are found clustered at the stem base, as well as alternately arranged along the stem. Leaves have simple hairs on the surface and are hairless beneath, and are pinnatifid, with stem leaves that are sessile or on short petioles with auriculate bases. Leaves are 4-13 cm long and 0.5-3 cm wide and are oblong in profile with leaf edges that range from sinuous to pinnately divided. This plant produces small yellow flowers from May to September that have 4 oblong to spatula-shaped petals, which are shorter than the 4 sepals. Pods are egg-shaped to short-cylindrical and are constricted in the middle.
Two varieties of blunt-leaved watercress occur in Alberta: var. curvipes, which have egg-shaped to pear-shaped pods that taper to a point; and var. truncata, which have short, cylindrical pods with a square tip and are more than twice as wide than long when mature. Another similar, rare annual species, slender yellow cress (Rorippa tenerrima), can be distinguished from blunt-leaved watercress by the presence of tiny, nipple-shaped bumps (papillae) known as siliques.
Blunt-leaved watercress is an obligate to facultative wetland plant, which can be found growing in moist ground such as wetlands, mud flats, shores, roadsides, stream beds and banks, and wet meadows, in southern and central Alberta. It is common for this plant to be found in the seasonal zone of a prairie pothole wetland that experiences annual cultivation, or the bank of a seasonal drainage where hoof shear from cattle or seasonal flooding maintains bare soil.
Blunt-leaved watercress has a global conservation status rank of G5 (Secure), and nationally it is not ranked (NNR). In Alberta and Saskatchewan, blunt-leaved watercress has a conservation status rank of S3 (Vulnerable), and in BC it is not ranked (SNR) and in Ontario its ranking is not applicable (SNA).
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All photos by L. Hamilton
 Kershaw, L.; Gould, J.; Johnson, D.; Lancaster, J. 2001. Rare vascular plants of Alberta. Univ. Alberta Press, Edmonton, Alberta and Nat. Resour. Can., Can. For. Serv., North. For. Cent., Edmonton, Alberta
 Kershaw, L.; Gould, J.; Johnson, D.; Lancaster, J. 2001. Rare vascular plants of Alberta. Univ. Alberta Press, Edmonton, Alberta and Nat. Resour. Can., Can. For. Serv., North. For. Cent., Edmonton, Alberta.