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

Watercress 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, creeping, hairless

Leaves:

basal and on the stem, alternate, short-stalked, may have ear-like lobes at base, 2 – 6 cm long, 0.5 – 1.5 cm wide, pinnately lobed, lobes downward pointing, entire to sparsely toothed, tip obtuse, hairless

Inflorescence:

unbranched, terminal or axillary; flowers stalked

Flowers:

sepals 0.8 – 1.4 mm long; petals 0.7 – 0.9 mm long; stamens 6; stigma not expanded

Fruits:

pod 4 – 6 mm long, 1 – 1.5 mm wide, 4 – 5.5 times longer than wide, 1.5 – 2 times longer than fruit stalks, cylindrical, slightly incurved, not constricted near the middle, minutely bumpy; style tapered, gradually merging to fruit; stalks slightly divergent to ascending, may have minute bumps; seeds 20 – 40 per pods, 0.6 – 0.8 mm long

*KEY TO RORIPPA* IN SASKATCHEWAN**

1 Petals longer than sepals	2
1 Petals shorter than or equal to sepals	4

2 Middle and upper leaves toothed to nearly entire, not lobed; stalks usually 3 – 4 times longer than fruit; pods spherical to subspherical	R. austriaca
2 Middle and upper leaves lobed, the divisions toothed; stalks only slightly longer than fruit; pods cylindrical	3

3 Stems erect; leaves and stem hairless or sparingly hairy, lacking hair-like epidermal outgrowths; leaf divisions tapered, toothed	R. sylvestris
3 Stems creeping; leaves and stems with hair-like epidermal outgrowths; leaf divisions obtuse, entire to toothed	R. sinuata

4 Stems sparingly to densely hairy below	5
4 Stems hairless throughout	7

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

6 Stems sparsely hairy below; pods slightly wider in the middle, 3 – 9 mm long	R. palustris var. fernaldiana
6 Stems densely hairy below; pods subspherical, 2 – 5.5 mm long	R. palustris var. hirsuta

7 Fruiting styles straight; pods 2 – 4 times longer than wide, surface smooth, constricted at center	R. curvipes var. truncata
7 Fruiting styles tapering towards the tip; pods more than 4 times as long as wide, surface minutely bumpy, not constricted at center	R. tenerrima