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simple-leaf tick trefoil

Habit Herbs, perennial. Herbs, perennial.
Stems

prostrate, 100–200(–300) cm, sparsely to densely patent-pubescent and uncinate-puberulent.

ascending to erect, branched, 30–80 cm, inconspicuously uncinate-puberulent or glabrescent.

Leaves

trifoliolate;

stipules often caducous, sometimes persistent, ovate or narrowly ovate, 4.5–8 mm;

petiole 28–50 mm;

leaflet blades ovate or rhombic-ovate, lateral veins inconspicuous, arcuate along margin, apex acute or obtuse, surfaces sparsely strigose;

terminal blade 30–70 × 20–50 mm, length 1.4–2 times width.

unifoliolate;

stipules ± persistent, narrowly ovate-deltate, 3–3.5 mm;

petiole 6–11 mm;

leaflet blades ovate to narrowly ovate, 30–80 × 10–30 mm, length (2–)2.5–5 times width, apex acute or obtuse, with paler patches along midrib adaxially, surfaces uncinate-puberulent and villous.

Inflorescences

lax-flowered, ascending, terminal and branched, also axillary and unbranched;

rachis uncinate-puberulent;

primary bracts caducous, ovate, 3–4 mm.

often numerous, slender and flexuous, branched or unbranched;

rachis densely uncinate-puberulent and villous;

primary bracts narrowly ovate, 1–2 mm.

Pedicels

7–9 mm.

4–10 mm.

Flowers

calyx 2.5–3.5 mm, uncinate-puberulent, tube 1 mm;

abaxial lobes 2 mm, lateral lobes 1.5 mm;

corolla purple, 8–9.5 mm.

calyx 2.5–3 mm, puberulent and sparsely pilose, tube 1 mm;

abaxial lobes 2–3 mm, lateral lobes 2 mm, adaxial connate nearly to apex;

corolla pink to purple, 4–5 mm.

Loments

sutures obtusely dentate abaxially, sinuate adaxially;

connections adaxial, 1/4–1/3 as broad as segments;

segments 3 or 4, deltate-rhombic, 6–8 × 4–5 mm, obtusely angled abaxially, straight or slightly convex adaxially, uncinate-pubescent;

stipe 2 mm.

margins slightly involute when young, sutures crenate abaxially, sinuate adaxially;

connections adaxial, 1/5 as broad as segments;

segments 3–5, elliptic to obovate, 2.5–6 × 3–3.5 mm, rounded abaxially, convex adaxially, sparsely uncinate-puberulent, sutures glabrous;

stipe 1.5–2.5 mm.

2n

= 22.

Desmodium ×humifusum

Desmodium psilophyllum

Phenology Flowering summer–fall. Flowering summer–fall.
Habitat Woodland openings and edges, powerline cuts, near exposed limestone. Mountain woodlands, creek beds, terraces.
Elevation 0–300 m. (0–1000 ft.) 1000–2200 m. (3300–7200 ft.)
Distribution
from FNA
CT; DE; IN; MA; MD; MO; NJ; NY; PA
[BONAP county map]
from FNA
AZ; TX; Mexico (Baja California Sur, Chiapas, Chihuahua, Coahuila, Durango, Hidalgo, Puebla, San Luis Potosí, Sinaloa, Sonora, Zacatecas)
[WildflowerSearch map]
[BONAP county map]
Discussion

Desmodium ×humifusum had been recognized as a species, but J. A. Raveill (2002) confirmed a hybrid origin from D. paniculatum and D. rotundifolium by allozyme electrophoresis. Desmodium × humifusum is likely to occur more widely than reported. It is in the Center for Plant Conservation’s National Collection of Endangered Plants as D. humifusum.

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

Desmodium psilophyllum is known in the flora area from southern Arizona to western and central Texas at the edge of Edwards Plateau; it is not known from New Mexico.

(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. retinens, D. rosei, D. rotundifolium, D. scopulorum, D. scorpiurus, D. sessilifolium, D. strictum, D. tenuifolium, D. tortuosum, D. triflorum, D. tweedyi, D. viridiflorum
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. 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
Synonyms Hedysaum humifusum, Meibomia humifusa Meibomia psilophylla
Name authority (Muhlenberg ex Bigelow) L. C. Beck: Bot. North. Middle States, 86. (1833) — (as species) Schlechtendal: Linnaea 12: 310. (1838)
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