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northern tansy-mustard

blunt tansy mustard

Habit Annuals or biennials; eglandular or glandular distally; glabrate to moderately pubescent, trichomes dendritic, sometimes mixed with simple ones. Biennials; glandular or eglandular; finely pubescent, often canescent, trichomes dendritic, sometimes mixed with simple ones.
Stems

erect, unbranched or sometimes branched distally, (0.5–)1.5–11(–18) dm.

erect, unbranched basally or branched proximally and/or distally, 4–12(–15) dm.

Basal leaves

petiole 0.5–5 cm;

blade pinnate or, sometimes, 2-pinnate, broadly oblanceolate to ovate in outline, 2.5–11.4(–15.2) cm, lateral lobes lanceolate, (to 10 × 4 mm), margins incised.

petiole 0.5–3.7 cm;

blade pinnate, oblanceolate to obovate or ovate in outline, 1–6 cm, lateral lobes (2–5 pairs), oblanceolate to linear or narrowly lanceolate, (7–25 × 2–10 mm), margins usually entire or serrate, rarely incised, (apex obtuse).

Cauline leaves

sessile or shortly petiolate;

blade smaller distally, distal lobes often narrower, surfaces often glabrous or sparsely pubescent.

sessile or shortly petiolate;

blade smaller distally, distal lobes often narrower, surfaces densely pubescent.

Racemes

elongated or not in fruit, (flowers overtopped by developing fruits).

considerably elongated in fruit.

Flowers

sepals erect, yellowish, oblong, 1.6–2.7 mm, glabrous;

petals narrowly oblanceolate, 2–2.5 × 0.3–0.6 mm;

median filaments 2.5–3.5 mm;

anthers 0.3–0.4 mm.

sepals spreading or sometimes ascending, greenish to yellowish, oblong, 1–2 mm, densely pubescent, (trichomes dendritic, sometimes mixed with glandular papillae);

petals oblanceolate, 1–2 × 0.5–0.7 mm (equaling or shorter than sepals);

median filaments 1.4–2 mm;

anthers 0.2–0.3 mm.

Fruiting pedicels

divaricate to ascending, (often recurved in age), slender, (3–)4–9(–13) mm.

ascending to divaricate, straight, 6–15 mm.

Fruits

erect to widely spreading, narrowly linear, slightly torulose, (9–)14–30(–34) × 0.6–1.1 mm, (usually terete, rarely slightly flattened, often curved inward);

valves each with obscure midvein;

septum not veined;

ovules 30–62 per ovary;

style obsolete, 0.07–0.3 mm, glabrous.

divaricate to suberect, linear, slightly torulose, 10–20(–23) × 0.7–1 mm, (acute at both ends);

valves each with distinct midvein, (sparsely to densely pubescent);

septum not veined;

ovules 16–40 per ovary;

style 0.1–0.2 mm, glabrous.

Seeds

uniseriate, light brown, narrowly oblong, 1–1.5 × 0.3–0.5 mm.

uniseriate or biseriate, light brown, oblong, 0.7–1.1 × 0.5–0.6 mm.

2n

= 14.

= 14.

Descurainia sophioides

Descurainia obtusa

Phenology Flowering Jun–Sep. Flowering May–Sep(-Oct).
Habitat Open meadows, eroded peat, roadsides, disturbed and waste sites, rocky outcrops, mining dumps, gravelly grounds, stream banks, gullies Gravelly grounds, sandy areas, disturbed sites, open forests, plateaus, abandoned mine areas, dry streams and washes
Elevation 0-1000 m (0-3300 ft) 1500-2600 m (4900-8500 ft)
Distribution
from FNA
AK; BC; MB; NT; NU; YT; Asia (Russian Far East, Siberia)
[BONAP county map]
from FNA
AZ; NM; NV; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
Discussion

As circumscribed here, Descurainia obtusa is a relatively uniform, diploid species. It probably was involved as a parent of D. adenophora, which is a hexaploid readily distinguished by characters discussed thereunder.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 7, p. 529. FNA vol. 7, p. 525.
Parent taxa Brassicaceae > tribe Descurainieae > Descurainia Brassicaceae > tribe Descurainieae > Descurainia
Sibling taxa
D. adenophora, D. brevisiliqua, D. californica, D. incana, D. incisa, D. kenheilii, D. longepedicellata, D. nelsonii, D. obtusa, D. paradisa, D. pinnata, D. sophia, D. torulosa
D. adenophora, D. brevisiliqua, D. californica, D. incana, D. incisa, D. kenheilii, D. longepedicellata, D. nelsonii, D. paradisa, D. pinnata, D. sophia, D. sophioides, D. torulosa
Synonyms Sisymbrium sophioides, Hesperis arctica, Sisymbrium arcticum, Sophia sophioides Sophia obtusa, Sisymbrium obtusum
Name authority (Fischer ex Hooker) O. E. Schulz: in H. G. A. Engler, Pflanzenr. 86[IV,105]: 316. (1924) (Greene) O. E. Schulz: in H. G. A. Engler, Pflanzenr. 86[IV,105]: 321. (1924)
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