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Arizona tick trefoil

Santa Rita Mountain ticktrefoil

Habit Herbs, perennial. Herbs, perennial, diffuse; base woody, rootstock woody.
Stems

erect or ascending, usually striate, sparsely branched, 20–80 cm, pubescent.

erect, ascending, or procumbent, usually striate, 30–60(–100) cm, sparsely to densely pilose and uncinate-pubescent.

Leaves

trifoliolate;

stipules caducous, narrowly ovate, 6–8 mm;

petiole 1–5 mm;

leaflet blades narrowly oblong-elliptic to linear, apex acute, surfaces villosulous;

terminal blade 40–60 × 4–10 mm, length 3.5–10 times width.

trifoliolate, sometimes unifoliolate proximally;

stipules persistent, recurved, subulate, 2–3 mm;

petiole 7–25 mm;

leaflet blades usually oblong-ovate to narrowly so, sometimes broadly elliptic to oblong, apex obtuse or acute, surfaces sparsely uncinate-puberulent;

terminal blade 10–30(–35) × 8–10 mm, length 1–3.5 times width.

Inflorescences

usually unbranched;

rachis uncinate-puberulent;

primary bracts caducous, broadly ovate, 4.5–5.5 mm.

usually unbranched, sometimes branched;

rachis patent uncinate-puberulent;

primary bracts narrowly ovate, 2.5–3 mm.

Pedicels

8–15 mm.

8–15 mm.

Flowers

calyx 3 mm, uncinate-puberulent, lobes pubescent, tube 1.2 mm;

abaxial lobes 2 mm, lateral lobes 1.5 mm;

corolla blue-purple, 5–6 mm.

calyx 1.5–2.5 mm, pubescent, tube 1 mm;

abaxial lobes 1.5 mm, lateral lobes 1 mm;

corolla pink-purple, 4–5 mm.

Loments

sutures undulate abaxially, crenate adaxially;

connections adaxial, 1/3 as broad as segments;

segments (2 or)3–5, semiorbiculate, 4–5(–6) × 4 mm, rounded abaxially, convex adaxially, uncinate-puberulent;

stipe 1–2 mm.

sutures subequally crenate;

connections central, 1/5–1/4 as broad as segments;

segments 2–7, rounded or broadly elliptic, 2.5–3 × 2.5 mm, abaxially and adaxially rounded, glabrous or slightly puberulent;

stipe 1–2 mm.

2n

= 22.

Desmodium arizonicum

Desmodium retinens

Phenology Flowering summer–fall. Flowering late summer–fall.
Habitat Oak-juniper or pine wood­lands, canyons, roadsides. Wooded or grassy rocky slopes, oak or oak-pine forests.
Elevation 1700–2500 m. (5600–8200 ft.) 1400–2100 m. (4600–6900 ft.)
Distribution
from FNA
AZ; NM; Mexico (Baja California, Chihuahua, Sinaloa, Sonora, Tamaulipas)
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; Mexico; Central America (Guatemala)
[BONAP county map]
Discussion

In the flora area, Desmodium arizonicum is known from southeastern Arizona and adjacent New Mexico.

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

Desmodium retinens is known in the flora area from Cochise, Graham, Pima, and Santa Cruz counties.

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

Source FNA vol. 11. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae > Desmodium Fabaceae > subfam. Faboideae > Desmodium
Sibling taxa
D. batocaulon, D. canadense, D. canescens, D. cinerascens, D. cuspidatum, D. floridanum, D. grahamii, D. gramineum, D. illinoense, D. incanum, D. intortum, D. laevigatum, D. lindheimeri, D. lineatum, D. marilandicum, D. metcalfei, D. nuttallii, D. ochroleucum, D. paniculatum, D. procumbens, D. psilocarpum, D. psilophyllum, D. retinens, D. rosei, D. rotundifolium, D. scopulorum, D. scorpiurus, D. sessilifolium, D. strictum, D. tenuifolium, D. tortuosum, D. triflorum, D. tweedyi, D. viridiflorum, D. ×humifusum
D. arizonicum, D. batocaulon, D. canadense, D. canescens, D. cinerascens, D. cuspidatum, D. floridanum, D. grahamii, D. gramineum, D. illinoense, D. incanum, D. intortum, D. laevigatum, D. lindheimeri, D. lineatum, D. marilandicum, D. metcalfei, D. nuttallii, D. ochroleucum, D. paniculatum, D. procumbens, D. psilocarpum, D. psilophyllum, D. rosei, D. rotundifolium, D. scopulorum, D. scorpiurus, D. sessilifolium, D. strictum, D. tenuifolium, D. tortuosum, D. triflorum, D. tweedyi, D. viridiflorum, D. ×humifusum
Synonyms Meibomia arizonica D. wislizeni, Meibomia retinens
Name authority S. Watson: Proc. Amer. Acad. Arts 20: 363. (1885) Schlechtendal: Linnaea 12: 311. (1838)
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