Sequoia False Goldenaster

Heterotheca monarchensis grows only in Kings River Canyon, northeastern Fresno County. It can be superficially similar to densely hairy specimens of H. sessiliflora var. bolanderioides and to individuals of subsp. sessiliflora that are silvery white, but those usually have ovate-lanceolate distal cauline leaves, while H. monarchensis has oblanceolate ones. All three can have heads partially surrounded by distal leaves and long, subtending, leaflike bracts. Their ranges do not overlap, however. Specimens of H. monarchensis can be confused with H. villosa varieties; the latter lack the long, thin corolla hairs. The species has a small number of known populations and is therefore of conservation concern.

Perennials, 9–17.5 cm; taprooted. Stems 1–25+, ascending-erect, moderately to densely hispid. Leaves: proximal cauline petiolate, blades oblanceolate to obovate, 11–17(–25) × 2–3.7(–5) mm, bases cuneate, margins ± undulate, entire, strigoso-ciliate (proximal cilia long, spreading, numerous), apices acute, faces moderately to densely hispido-strigose, sparsely stipitate-glandular; distal narrowly oblanceolate, little reduced distally. Heads 1–2(–5), borne singly or in corymbiform arrays, branches ascending. Peduncles 2–5(–10) mm, densely hispid, sparsely stipitate-glandular; bracts leaflike, sometimes surpassing involucres, those subtending heads narrower than leaves. Involucres cylindro-turbinate (campanulate upon drying), 6–7.5(–8.5) mm. Phyllaries in 3–4 series, unequal (outer lengths ¹ / 4 – ¹ / 2 inner), margins scarious, faces moderately strigose, sparsely stipitate-glandular. Ray florets (8–)12–16(–19); laminae 10–14 × 1–2 mm. Disc florets 30–45; corollas ± ampliate, 5–6 mm, tubes sparsely pilose distally, lobes 0.45–0.7 mm, sparsely pilose (hairs 0.2–0.6 mm). Cypselae monomorphic, obconic, somewhat compressed, 2–3 mm, ribs 9–11, shallow, faces moderately strigose; pappi off-white, outer of linear scales 0.25–0.5 mm, inner of 25–40 bristles 5–6.5 mm, longest weakly clavate. 2n = 18.

Heterotheca monarchensis is a rare species of flowering plant in the family Asteraceae known by the common names monarch goldenaster and sequoia false goldenaster. It is endemic to Fresno County, California, where it is known from only one location near Boyden Cave in the Kings River Canyon. It grows in the limestone cliffs of this Sierra Nevada river canyon, along with a few other rare local endemics. The plant was discovered in July, 1995, and described to science as a new species in 1996.

This is a perennial herb anchored in the rocky substrate by a taproot and producing one to many erect, spreading stems up to about 18 centimeters tall. The leaves have lance-shaped or oval blades which are densely hairy and bristly in texture, with some resin glands. They measure up to 2.5 centimeters long by a few millimeters in width and do not become much smaller toward the ends of the branches. The inflorescence contains one to five flower heads, each with up to 19 yellow ray florets measuring 1 to 1.5 centimeters in length. At the center are many hairy yellow disc florets.

There are approximately 500 individuals of this plant in existence. It is impacted by introduced plant species, especially red brome (Bromus madritensis subsp. rubens).