Descurainia nelsonii
Descurainia paradisa
Nelson's tansy-mustard, sagebrush tansymustard
Great Basin tansy mustard, Nevada tansymustard, paradise tansymustard
erect, usually branched basally or slightly distally, rarely unbranched, (0.7–)0.9–3.2(–4.5) dm.
erect, branched basally and distally, (often purplish), (1–)1.5–3.2(–4.1) dm.
petiole 0.5–1.5 cm;
blade pinnate, ovate or oblong in outline, 0.8–2.5 cm, lateral lobe (2–5 pairs), margins dentate or entire.
(soon withered);
petiole 0.3–1.3 cm;
blade pinnate, oblanceolate to obovate in outline, 1.5–3 cm, lateral lobes oblong to linear or lanceolate, (1–5 × 0.3–1 mm), margins entire or dentate.
sessile or shortly petiolate;
blade smaller distally, distal lobes often narrower, sparsely to moderately pubescent.
sessile;
blade smaller distally, distal lobes often narrower, surfaces moderately to densely pubescent.
considerably elongated in fruit.
considerably elongated in fruit.
sepals ascending, yellowish, oblong, 0.7–1.2 mm, pubescent;
petals narrowly oblanceolate, 0.8–1.2 × 0.2–0.4 mm;
median filaments 1–1.5 mm;
anthers 0.1–0.2 mm.
sepals spreading to ascending, pale yellow, oblong, 0.8–1.2 mm, pubescent;
petals oblanceolate, 0.9–1.3 × 0.2–0.5 mm;
median filaments 0.8–1.2 mm;
anthers 0.1–0.2 mm.
divaricate-ascending (often at 20–45º angle), straight, (1.5–)2.5–7(–10) mm.
divaricate to ascending, straight, 2.5–7(–9) mm.
erect or ascending, linear, not or slightly torulose, (0.4–)5–8(–10) × 0.7–1 mm;
valves each with distinct midvein;
septum not veined;
ovules 6–12 per ovary;
style 0.1–0.2 mm, glabrous.
divaricate to erect, usually obovoid to clavate, rarely broadly ellipsoid, not torulose, 2–5 × 1–2 mm, (acute basally, obtuse apically);
valves each with obscure midvein;
septum not veined;
ovules 4–10 per ovary;
style 0.05–0.3 mm, glabrous.
uniseriate, brown, oblong, 0.6–0.8 × 0.4–0.5 mm.
uniseriate or biseriate, brown, oblong, 0.8–1.2 × 0.5–0.6 mm.
= 14.
Descurainia nelsonii
Descurainia paradisa
Descurainia nelsonii was treated by L. E. Detling (1939) and R. C. Rollins (1993) as a subspecies of D. pinnata, but the latter in the sense of these authors is not monophyletic, comprising instead either four or two unrelated species, respectively. ITS molecular data (B. E. Goodson 2007) suggest that D. nelsonii is most closely related to D. longepedicellata and D. paradisa. It can be distinguished from the latter species by its linear fruits with cuneate tips; D. paradisa has obovoid fruits with rounded tips. Descurainia nelsonii resembles D. pinnata subsp. brachycarpa in the orientation of fruiting pedicels and in having short styles (to 0.3 mm) and small seeds (to 1 × 0.5 mm). It differs in being branched (versus simple) at base and in having smaller flowers (petals 0.7–1 versus 1.5–2.6 mm), fewer ovules (6–12 versus 16–40) per ovary, linear (versus subclavate) fruits, and uniseriate (versus biseriate) seeds.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Although L. E. Detling (1939) reduced Descurainia paradisa to a subspecies of D. pinnata, molecular data (B. E. Goodson 2007) clearly show that it should not be included in that species. The boundaries of D. paradisa in its northern and southern ranges tend to be blurred relative to D. nelsonii and D. pinnata, respectively.
R. C. Rollins (1993) and N. H. Holmgren (2005b) recognized some of the Nevada plants of Descurainia paradisa that have eglandular racemes as a subspecies and variety (nevadensis), respectively. This poorly delimited division of the species is artificial, and both glandular and eglandular forms are sometimes found within individual populations of most species. They also indicated that nevadensis has styles 0.2–0.3 mm (versus 0.05–0.15 mm in D. paradisa), but this distinction is equally unreliable. Indeed, the style length and the presence versus absence of glands are not inherited together. Some of the eglandular plants have styles to 0.1 mm (e.g., Williams & Tiehm 86-51-1, GH). It is likely that some of the plants identified as nevadensis are of hybrid origin involving other species, especially D. nelsonii.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
USDA Plants Database
