Yerba De San Juan

Pectis humifusa has been reported once from Florida (D. J. Keil 1975c), where it is probably adventive. In the Lesser Antilles, it occurs most frequently in the salt spray zone near the seashore; on some islands, it occurs inland as well.

Annuals or perennials, 2–25 cm (across; bases often ± woody); herbage not scented. Stems prostrate (mat-forming, densely leafy), puberulent (in decurrent lines). Leaves oblong-oblanceolate to obovate, 3–17 × 1.5–4 mm wide, margins with 2–6 pairs of setae 1–2 mm, faces glabrous (dotted with scattered, round oil-glands 0.1–0.2 mm). Heads borne singly or in congested, (leafy) cymiform arrays. Peduncles 1–12 mm. Involucres campanulate. Phyllaries distinct, obovate, 4.5–6 × 2–4 mm (faces densely dotted with scattered, circular oil-glands 0.05–0.2 mm). Ray florets 5; corollas 3.5–5 mm. Disc florets 12–21; corollas 2.5–3.5 mm (2-lipped). Cypselae 2.5–4 mm, mostly puberulent (ray cypselae abaxially glabrous); ray pappi of 2–3 slender, aristate scales 1.5–2.5 mm plus 2–10 lacerate scales or bristles; disc pappi of 4–15, antrorsely scabrid bristles or aristate scales 2–3 mm plus 0–15 bristles or scales. 2n = 72.

Pectis humifusa Sw. Prodr. 114. 1788
Chthonia repens Cass. Diet. Sci. Nat. 27: 204. 1823.
Pertw fros/ra/a Spreng. Syst. 3: 572. in part. 1826. Hoi P. proslrata Ca.v. 1797.
Pectis serpllifolia Less. Linnaea 6: 715. 1831.
Pectis Sieb'eri hess. Linnaea 6: 717. 1831.
Lorenlea humifusa Less. Linnaea 6: 719. in part. 1831.
Chthonia humifusa Cass.; Steud. Nom. Bot. ed. 2. 1: 360. 1840.
A diffuse annual; stem branched from the base, prostrate or procumbent, sometimes rooting, 5-40 cm. long, short-pilose along two decurrent lines; leaves oblanceolate to obovate, 3-12 mm. long, 2-4 mm. wide, usually rounded or obtuse at the apex, with 2-6 pairs of bristles towards the base, scabrous-cUiolate on the margins, paler beneath; glands numerous, minute, irregularly scattered; heads solitary, sessile or subsessile at the ends of the branchlets; involucre 5-6 mm. high, 2-4.5 mm. broad; bracts 5 (rarely 3), elliptic or oval, obtuse, rounded or retuse at the apex, strongly keeled at the base, with several round glands at the apex; raj'-flowers 5 (rarely 3); Ugules 3-5 mm. long; disk-flowers 10-25; corollas about 3 mm. long; achenes 2.5-3 mm. long, sparingly pubescent or glabrate; squamellae of the disk-flowers 5-20, of the ray-flowers 2-10, lanceolate to subidate, aristate, incised, very unequal.
Type locality: Guadeloupe.
Distribution: Santo Domingo to Barbados.

Pectis humifusa, the yerba de San Juan, is a summer blooming annual plant of the genus Pectis. In the Lesser Antilles, it occurs most frequently in the salt spray zone near the seashore; on some islands, it occurs inland as well. Its floral region is Puerto Rico, The Virgin Islands and Florida.