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Santa Rita Mountain ticktrefoil

Dixie tick trefoil

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

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

erect, 50–200 cm, medially uncinate-pubescent and patent-villous.

Leaves

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.

trifoliolate;

stipules persistent, often patent or reflexed, obliquely ovate and apex acuminate or narrowly ovate and apex aristate, 3–12.5 mm, base amplexicaul;

petiole 8–50 mm;

leaflet blades narrowly ovate to ovate, elliptic, or rhombic, apex obtuse or acute, surfaces obscurely prominently reticulate-veined abaxially, uncinate-puberulent and strigose or subappressed-villous;

terminal blade (20–)40–150 × 10–50 mm, length 2–3 times width.

Inflorescences

usually unbranched, sometimes branched;

rachis patent uncinate-puberulent;

primary bracts narrowly ovate, 2.5–3 mm.

branched or unbranched;

rachis villous (often with bulbous hairs) and uncinate-puberulent, or only uncinate-puberulent;

primary bracts caducous, narrowly ovate, 4 mm.

Pedicels

8–15 mm.

10–15 mm.

Flowers

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.

calyx 1.5–3 mm, uncinate-puberulent, tube to 1 mm;

abaxial lobes 2 mm, lateral lobes 1 mm;

corolla lavender, 4–6 mm.

Loments

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.

margins alternately involute and revolute, sutures equally crenate, twisted conspicuously when young;

connections central, 1/4 as broad as segments;

segments (3 or)4–7, orbiculate, broadly elliptic, or rhombic, 3–4.5 × 3–3.5 mm, rounded abaxially and adaxially, densely uncinate-pubescent;

stipe 0.5–1 mm.

2n

= 22.

Desmodium retinens

Desmodium tortuosum

Phenology Flowering late summer–fall. Flowering summer–fall (year-round).
Habitat Wooded or grassy rocky slopes, oak or oak-pine forests. Open, dis­turbed sites, ruderal areas, pinelands, savannas.
Elevation 1400–2100 m. (4600–6900 ft.) 0–300 m. (0–1000 ft.)
Distribution
from FNA
AZ; Mexico; Central America (Guatemala)
[BONAP county map]
from FNA
AL; AR; FL; GA; LA; MS; NC; SC; TX; Central America; South America; Mexico (Chiapas, Colima, Guerrero, Jalisco, Nayarit, Oaxaca, Sinaloa, Sonora); West Indies [Introduced in North America; introduced also in Asia, Africa, Indian Ocean Islands, Pacific Islands, Australia]
[WildflowerSearch map]
[BONAP county map]
Discussion

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.)

Desmodium tortuosum is most easily distinguished from its relatives by the thick leaflets with prominent reticulate venation, the large persistent stipules, and the long, stiff, ascending to spreading pedicels (B. G. Schubert 1980).

(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. 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
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. retinens, D. rosei, D. rotundifolium, D. scopulorum, D. scorpiurus, D. sessilifolium, D. strictum, D. tenuifolium, D. triflorum, D. tweedyi, D. viridiflorum, D. ×humifusum
Synonyms D. wislizeni, Meibomia retinens Hedysarum tortuosum, Meibomia purpurea, M. tortuosa
Name authority Schlechtendal: Linnaea 12: 311. (1838) (Swartz) de Candolle in A. P. de Candolle and A. L. P. P. de Candolle: Prodr. 2: 332. (1825)
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