Tropical Threefold

The earliest botanical name for the plants here called Trixis inula is Inula trixis Linnaeus, 1760. In 1763, Linnaeus changed the name from Inula trixis to Perdicium radiale, which was based on the same type and is illegitimate under today’s rules of botanical nomenclature because the epithet trixis should have been used in 1763. The name Trixis radialis (Linnaeus) Kuntze, 1891, was based on Perdicium radiale of Linnaeus and has been used by some botanists; it is superfluous and illegitimate under today’s rules.

Plants 30–300+ cm (much branched). Leaves usually spread-ing; petioles 1–3 mm; blades linear-lanceolate to lanceolate or elliptic, 2.5–16.5 cm, bases attenuate to ± truncate, margins entire or denticulate (± flat), induments: margins and some-times abaxial midveins with glandless and glandular hairs, otherwise glabrous; stomates on abaxial faces. Heads in corymbiform or paniculiform arrays. Peduncles 1–20(–25) mm, little, if at all, inflated distally. Calyculi of 3–5 linear to lanceolate (rarely ovate) bractlets 2.5–17 mm. Phyllaries usually 8, linear to oblong, 8–13(–15) mm, apices acute. Florets (8–)10–15; corolla tubes 5–9 mm, outer lips 4–7.5 mm, inner 3.5–5.5 mm. Cypselae 4.5–9 mm, papilla-like double hairs not producing mucilage when wetted; pappi 7–11 mm. 2n = 54.

Trixis inula, the tropical threefold, is a plant species native to Texas, Mexico, Central America, northern South America, and the West Indies. It is found on open, sandy sites such as roadsides, thorn scrub, thickets, etc.

Trixis inula is a much-branched shrub up to 300 cm (10 feet) tall. It has lanceolate to elliptic leaves up to 17 cm (7 inches) long. Yellow flower heads are borne in paniculate arrays.