Shrubs, to 3 m. Leaves slightly to highly xerophytic as phyllodes, 0.8–5 cm, finely hairy; stipules caducous; extrafloral nectaries 1–8, between first leaflet pair, sometimes also 1 or all subsequent pairs, sessile; leaf­let pairs 0–8, blades linear to narrowly elliptic, 20–70 × 1–8 mm. Racemes 2–10-flowered; bracts early caducous. Pedicels 4–15 mm. Flowers slightly asym­metric, enantiostylous; calyx yellowish to greenish; corolla yellow, longest petal 6–10 mm; androecium not heterantherous, stamens 10, staminodes 0; anthers 1.5–5 mm, dehiscing by 2 pores, apical appendage 0; gynoecium incurved, ovules unknown; ovary slightly hairy; style slightly incurved. Legumes pendulous, flat, straight or slightly curved, 20–80 × 6–12 mm, corrugated over seeds, indehiscent. Seeds dark brown or dull, obovoid. 2n = 28, 56.

Phenology: Flowering late fall–early spring.
Habitat: Rocky and desert sand and soils.
Elevation: 0–700 m.

Distribution

• Generated Map
• Legacy Map

Introduced; Ariz., Calif., Australia.

Discussion

Due to its remarkable morphological and genetic variation (especially in leaflet number and form), Senna artemisioides has a shifting taxonomic history. The species, as circumscribed by Randell, was divided into several morphological forms by B. R. Randell and B. A. Barlow (1998). Senna artemisioides, as presented here, encompasses four common morphological forms found in North America: subsp. filifolia Randell, subsp. petiolaris Randell, nothosubsp. sturtii (R. Brown) Randell, and subsp. zygophylla Randell. D. E. Symon (1998) considered individuals of subsp. petiolaris characterized by arcuate phyllodes to be a separate species, S. phyllodinea (R. Brown) Symon, mainly because of the absence of individuals with an intermediate leaf morphology transitioning to the phyllode shape. Although this argument is reasonable, S. phyllodinea has not been accepted and adopted in other floristic studies. It must be noted that phyllodes consist of the lateral compression of both the petiole and the rachis, and not only of the petiole, as reported by Randell and Barlow. Along the adaxial margin of the phyllode, there is, in fact, a reduced extrafloral nectary at each insertion place of the suppressed leaflets.

Selected References

None.

Lower Taxa

None.