Rorippa tenerrima |
Rorippa palustris |
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low yellow-cress, Modoc yellow-cress, slender yellowcress, watercress, yellow cress |
bog yellow cress, common yellow-cress, hispid yellowcress, marsh cress, marsh yellow-cress |
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Habit | Annuals; (terrestrial or of wet habitat, not submerged); glabrous throughout. | Annuals or, rarely, perennials; (short-lived, terrestrial or of wet habitat, not submerged); usually glabrous, rarely hirsute, (trichomes cylindrical). | ||||
Stems | (several-branched from base), prostrate to decumbent, branched distally, 0.7–3.5(–4) dm. |
(often simple from base), erect, branched distally, (0.5–)1–10(–14) dm, (sometimes hirsute proximally). |
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Basal leaves | not rosulate; blade margins pinnatifid. |
rosulate; blade [(4–)6–20(–30) cm × 10–50(–80) mm] margins lyrate-pinnatisect, (abaxial surface sometimes hirsute). |
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Cauline leaves | shortly petiolate, or (distal) sessile; blade oblong to oblanceolate or lanceolate, (lateral lobes linear, oblong to ovate, or obovate), 2–9(–11) cm × 7–20(–30) mm, (lateral lobes smaller than terminal), base not auriculate, margins pinnatifid, or (lateral lobes) entire, dentate, or sinuate. |
petiolate or subsessile; blade lyrate-pinnatisect, (lateral lobes oblong or ovate when present), (1.5–)2.5–10(–18) cm × (5–)8–25(–30) mm, (lateral lobes smaller than terminal), base auriculate or amplexicaul, margins subentire or irregularly dentate, sinuate, serrate, or crenate, (abaxial surface sometimes hirsute). |
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Racemes | elongated. |
often considerably elongated. |
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Flowers | sepals ascending, oblong, 0.7–1.3 × 0.4–0.7 mm; petals yellow, oblong to oblanceolate or spatulate, 0.5–0.8 × 0.1–0.3 mm; median filaments 0.8–1.2 mm; anthers ovate, 0.1–0.2 mm. |
sepals erect, oblong, 1.5–2.4(–2.6) × 0.5–1 mm; petals yellow or pale yellow, spatulate, (1.5–)1.8–2.5(–3) × 0.5–1.5(–2) mm; median filaments 1–2.5 mm; anthers ovate, 0.3–0.5 mm. |
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Fruiting pedicels | ascending to divaricate, (1–)1.5–3.2(–4.2) mm, straight. |
divaricate or slightly to strongly reflexed, straight or curved, (2.5–)3–10(–14) mm. |
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Fruits | siliques or silicles, curved-ascending, lanceolate to narrowly ovoid or oblong-lanceolate, 3–7(–9) × (0.8–)1–1.7(–2) mm (often slightly constricted at middle); valves papillate; ovules 20–80 per ovary; style (0.2–)0.5–1 mm. |
usually silicles, rarely siliques, often slightly curved, oblong, ellipsoid, or oblong-ovoid, (2.5–)4–10 × (1.5–)1.7–3(–3.5) mm; ovules 20–90 per ovary; style 0.2–1(–1.2) mm. |
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Seeds | biseriate, reddish brown, cordiform, 0.5–0.7 mm, colliculate. |
biseriate, brown to yellowish brown, ovoid or subglobose, 0.5–0.7(–0.9) mm (0.4–0.6(–0.7) mm diam.), colliculate. |
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Rorippa tenerrima |
Rorippa palustris |
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Phenology | Flowering Jun–Oct. | |||||
Habitat | Shores of lakes and ponds, mud flats, marshes, sand bars, moist grounds, streamsides | |||||
Elevation | 1300-3000 m (4300-9800 ft) | |||||
Distribution |
CA; CO; ID; MO; MT; ND; NE; NM; NV; OR; SD; TX; UT; WA; WY; AB; BC; SK; Mexico (Baja California, Chihuahua)
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AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NS; NT; ON; PE; QC; SK; YT; Europe; Asia [Introduced in n Mexico, South America, Australia]
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Discussion | Subspecies 2 (2 in the flora). Rorippa palustris is a highly variable species with controversial infraspecific taxonomy. B. Jonsell (1968) recognized four subspecies, of which one (subsp. palustris) is cosmopolitan and three are North American. R. L. Stuckey (1972) followed Jonsell but further divided the North American plants into eleven, poorly defined varieties. Division of the species into subspecies based solely on stem height and fruit length is artificial. The variation is continuous in every character, and the recognized infraspecific taxa represent only some of the extremes. Some collections cannot be adequately assigned to a given subspecies or variety, and of all the infraspecific taxa recognized, only two can be consistently separated from each other; they are recognized here as subspecies. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 7, p. 505. | FNA vol. 7, p. 501. | ||||
Parent taxa | Brassicaceae > tribe Cardamineae > Rorippa | Brassicaceae > tribe Cardamineae > Rorippa | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Radicula tenerrima | Sisymbrium amphibium var. palustre, Brachiolobos palustris, Cardamine palustris, Caroli-Gmelina palustris, Myagrum palustre, Nasturtium palustre, Radicula palustris | ||||
Name authority | Greene: Erythea 3: 46. (1895) | (Linnaeus) Besser: Enum. Pl., 27. (1821) | ||||
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