Species: Rorippa tenerrima Greene

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Rorippa tenerrima Greene

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TAXONOMY

Family:

Brassicaceae

Genus:

Rorippa

Species Synonyms:

none

Common Names:

watercress
Modoc yellowcress

DISTRIBUTION

Canada:

southern British Columbia - southern Alberta - southern Saskatchewan

Saskatchewan:

southern Saskatchewan; Cypress Hills to Rockglen

Ecoregion:

Cypress Upland; Mixed Grassland, Moist Mixed Grassland

HABITAT

Saskatchewan:

shores of small ponds, riverbanks

RARITY STATUS

Provincial Status According
to Harms (2003):

Threatened

Nature Conservancy Status:

G5 N2 S1

Saskatchewan Species at
Risk Status:

None

COSEWIC Status:

None

Rorippa tenerrima is threatened because it is rare or uncommon in Saskatchewan. This species is regionally restricted to one area of the province. The plants are usually locally numerous in localized areas.

SPECIES DESCRIPTION

Height:

5 – 20 cm long

Roots:

taproot

Stems:

annual, several, tufted, decumbent to prostrate, glabrous

Leaves:

basal and cauline, alternate, short-petiolate, may be auriculate, 2 – 6 cm long, 0.5 – 1.5 cm wide, pinnate-lyrate lobed, apex obtuse, glabrous, lobes entire to sparsely toothed

Inflorescence:

raceme terminal or axillary

Flowers:

calyx 0.8 – 1.4 mm long; corolla 0.7 – 0.9 mm long; stamens 6; style tapered, gradually merging to fruit; stigma not expanded

Fruits:

silique 4 – 6 mm long, 1 – 1.5 mm wide, 4 – 5.5 times longer than wide, 1.5 – 2 times longer than pedicels, cylindrical, slightly incurved, not constricted near the middle, papillae minute; pedicels slightly divergent to ascending, may have minute papillae; seeds 20 – 40 per silique, 0.6 – 0.8 mm long

*KEY TO RORIPPA* IN SASKATCHEWAN**

1 Corolla longer than calyx	2
1 Corolla shorter than or equal to calyx	4

2 Middle and upper leaves serrate to nearly entire, not pinnatifed; pedicels usually 3 – 4 times longer than fruit; siliques globose to subglobose	R. austriaca
2 Middle and upper leaves pinnatifed, the divisions toothed; pedicels only slightly longer than fruit; siliques cylindrical	3

3 Stems erect; leaves and stem glabrous or sparingly pubescent, lacking trichomes; leaf divisions acute, toothed	R. sylvestris
3 Stems decumbent to prostrate; leaves and stems with trichomes; leaf divisions obtuse, entire to denticulate	R. sinuata

4 Stems sparingly to densely hirsute below	5
4 Stems glabrous throughout	7

5 Leaves thin, upper and lower pinnatifed; pods 3 – 4 mm long	R. palustris var. palustris
5 Leaves firm, upper leaves dentate to shallowly lobed; pods 2 – 9 mm	6

6 Stems sparsely hirsute below; siliques slenderly ellipsoid, 3 – 9 mm long	R. palustris var. fernaldiana
6 Stems densely hirsute below; siliques subglobose, 2 – 5.5 mm long	R. palustris var. hirsuta

7 Fruiting styles straight; silique 2 – 4 times longer than wide, glabrous, constricted at center	R. curvipes var. truncata
7 Fruiting styles tapering towards the apex; silique more than 4 times as long as wide, with minute papillae, not constricted at center	R. tenerrima