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Mojave indigo-bush

Photo is of parent taxon
Habit Shrubs.
Stems

3–10 dm, gland-dotted distally when young, glands prickle-shaped, hairy to glabrate.

Branches

irregular, stiff;

sterile shoots often sharp-tipped.

Leaves

usually pinnate, sometimes unifoliolate distally, (0.3–)1–3.5(–5.5) cm;

leaflets (1 or 3)5–11, blades ovate, obovate, lanceolate, linear, elliptic, rhombic-elliptic, rhombic-ovate, or linear-oblanceolate, 2–14(–17) mm, terminal leaflet seldom longer than laterals, surfaces gland-dotted abaxially, silky-strigulose, villous-tomentulose to glabrate, loosely hairy, or glabrous.

0.3–3.5 cm;

leaflets (1 or)5 or 7(or 9), blades linear-oblanceolate to narrowly elliptic, 2–12 mm, surfaces silky-strigulose.

Racemes

loose;

rachis without thornlike tip in anthesis, (1–)1.5–12 cm;

bracts subulate to linear, 2.5–4 mm;

bracteoles present.

Flowers

calyx 5–9 mm, pilosulous to minutely puberulent, strigulose, silky-canescent, or glabrate, tube 3–4.5 mm, ribs prominent, broader adaxial intervals with 2 rows, narrower one with 1 row of 3–5 glands, lobes broadly lanceolate, triangular, or lanceolate, abaxial lobe often shorter;

corolla indigo-blue to violet;

banner flabellate to flabellate-ovate, 6.3–10 mm, base cuneate to auriculate, claw cuneate;

wings oblong to oblong-ovate, 5.4–8.2 × 2.2–3.5 mm;

keel obliquely obovate, 5.8–8.4 × 3.3–4.9 mm;

stamens (5.5–)6.5–9.8 mm;

filaments distinct to (3–)3.5–5.6 mm;

anthers (0.8–)0.9–1.3 mm, connective not gland-tipped.

calyx 5.2–6.9 mm, tube 3–4.2 mm, silky-canescent externally;

corolla indigo blue;

banner 6.3–7.8 mm;

keel 5.8–6.4 mm.

Legumes

ovoid-ellipsoid or obliquely ellipsoid, 8–10 mm, with scattered blister-glands, glands not confluent, glabrous or sparsely villosulous.

Seeds

(4.7–)5–6 mm.

2n

= 10.

Psorothamnus arborescens

Psorothamnus arborescens var. californicus

Phenology Flowering late winter–spring.
Habitat Stony, rocky, or sandy ground in creosote-bush scrub, regions transitional to oak-juniper-manzanita associations.
Elevation 100–1100 m. (300–3600 ft.)
Distribution
from USDA
sw United States; nw Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
Discussion

Varieties 4 (4 in the flora).

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

Variety californicus is known from the San Bernardino Mountains and adjacent desert regions.

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

Key
1. Calyces 7–9 mm, lobes to 3–5.4 mm.
→ 2
2. Leaflets (3 or)5 or 7, blades ovate to obovate, elliptic, or broadly lanceolate.
var. arborescens
2. Leaflets (5 or)7–11, blades linear to linear-oblanceolate.
var. pubescens
1. Calyces 5–6.9 mm, lobes to 1.8–3.7 mm.
→ 3
3. Calyx tube glabrate or puberulent; leaflet blades lanceolate to rhombic-ovate or -elliptic, surfaces loosely hairy or glabrous.
var. minutifolius
3. Calyx tube silky-canescent externally; leaflet blades linear-oblanceolate to narrowly elliptic, surfaces silky-strigulose.
var. californicus
Source FNA vol. 11. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae > Psorothamnus Fabaceae > subfam. Faboideae > Psorothamnus > Psorothamnus arborescens
Sibling taxa
P. emoryi, P. fremontii, P. kingii, P. polydenius, P. schottii, P. scoparius, P. spinosus, P. thompsoniae
P. arborescens var. arborescens, P. arborescens var. minutifolius, P. arborescens var. pubescens
Subordinate taxa
P. arborescens var. arborescens, P. arborescens var. californicus, P. arborescens var. minutifolius, P. arborescens var. pubescens
Synonyms Dalea arborescens Dalea californica, Parosela californica, Parosela californica var. simplicifolia, P. arborescens var. simplicifolius
Name authority (Torrey ex A. Gray) Barneby: Mem. New York Bot. Gard. 27: 33. (1977) (S. Watson) Sutherland: Gandhi & Vincent, J. Bot. Res. Inst. Texas 14: 188. (2020)
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