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spiny milkwort, spiny or cushion or showy milkwort

Habit Subshrubs or shrubs, multi-stemmed, 0.5–2.5(–6) dm.
Stems

prostrate to erect, sometimes glaucous, at least when young, glabrous or pubescent, hairs spreading to slightly incurved.

Leaves

subsessile to petiolate, petiole to 1(–2) mm;

blade obovate or elliptic, 4–31 × 0.8–11 mm, base cuneate, apex rounded or acute, surfaces densely to sparsely pubescent or subglabrous, hairs spreading to slightly incurved.

Racemes

terminal, sometimes reduced to (1 or)2–few flowers, 3–12.5 cm;

rachis thorn-tipped;

peduncle 0.1–0.5 cm;

bracts usually deciduous, rarely persistent, elliptic, ovate, or lanceolate.

Pedicels

(1.5–)3.5–10(–20.5) mm, glabrous or pubescent.

Flowers

pink to rose, wings (and other sepals) sometimes light green, distal keel yellow or green, (6–)8–12(–13) mm;

sepals deciduous, ovate, elliptic, or lanceolate, 2–7.2 mm, glabrous or pubescent;

wings obovate to elliptic-obovate, (5–)7–11.5(–12.2) × (2.3–)3–5.2(–5.9) mm, glabrous or pubescent;

keel (5.4–)6.2–10.5 mm, sac glabrous, beak oblong, 1–3 × 0.9–1.5 mm, glabrous.

Capsules

ellipsoid to obovoid, 4.3–8.8(–10) × 3.7–7.3 mm, base cuneate to rounded, margins with narrow, entire or slightly erose wing, glabrous or pubescent.

Seeds

3.3–4.9 mm, ± evenly and moderately densely pubescent, occasionally with glabrate patches;

aril 1.2–3.1 mm, lobes to 1/2 length of seed.

2n

= 18, 36.

Rhinotropis subspinosa

Phenology Flowering spring–mid summer.
Habitat Gravelly soils derived from limestone, shale, lava, or tuff, or crevices of soft calcareous rocks on eroded hills, open slopes and flats, in desert scrub, open pinyon-juniper woodlands, mountain brush, ponderosa pine woodlands.
Elevation 1300–2400 m. (4300–7900 ft.)
Distribution
from FNA
AZ; CA; CO; NM; NV; UT
[WildflowerSearch map]
[BONAP county map]
Source FNA vol. 10.
Parent taxa Polygalaceae > Rhinotropis
Sibling taxa
R. acanthoclada, R. californica, R. cornuta, R. heterorhyncha, R. intermontana, R. lindheimeri, R. maravillasensis, R. nitida, R. nudata, R. rimulicola, R. rusbyi
Synonyms Polygalasubspinosa s.
Name authority (S. Watson) J. R. Abbott: J. Bot. Res. Inst. Texas 5: 135. (2011)
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