Clustered frostweed Clustered frostweed

Cistus glomeratus Lagasca, Gen. Sp. Pl., 16. 1816; Helianthemum glomeratum (Lagasca) Lagasca

Subshrubs. Stems <from branched caudex and horizontal rootstocks>, ascending to erect, 10–60(–80) cm, stellate-pubescent, glabrescent. Leaves cauline; petiole 0–2 mm; blade oblanceolate, 10–25(–35) × 2–8(–14) mm, <base cuneate, margins nonrevolute, apex subacute>, surfaces stellate-tomentose, without simple hairs, lateral veins obscure or raised abaxially. Inflorescences terminal and axillary, glomerules and panicles; chasmogamous flowers 1–2 per panicle, <overtopping cleistogamous>, cleistogamous 2–10 per glomerule, <produced simultaneously with chasmogamous>. Pedicels 10–20 mm; bracts 2–5 × 0.2–0.8 mm. Chasmogamous flowers: outer sepals linear, 1–4 × 0.3 mm, inner sepals 3–7 × 1.8–3.2 mm, apex acute to acuminate; petals obovate, 4–9 × 3.5–6 mm; capsules 3.5–4.5 × 2–3 mm, glabrous. Cleistogamous flowers: outer sepals linear, 1–3 × 0.2–0.4 mm, inner sepals ovate or ovate-lanceolate, 2.4–5 × 1.2–3.6 mm, apex acute or acuminate; capsules 1.6–3.6 × 1.2–2.5 mm, glabrous.

Flowering Jun–Aug [throughout the year]. Dry montane oak woodlands; 2000–2400 m; Tex.; Mexico (Chihuahua, Durango, Nuevo León, San Luis Potosí, Sinaloa, Sonora, Zacatecas); Central America (Costa Rica, Guatemala, Honduras).

In the flora area, Crocanthemum glomeratum occurs only in the Chisos Mountains of western Texas. In Mexico and Central America, it is variable in foliage, flowers, and fruits; H. S. Daoud and R. L. Wilbur (1965) were unable to discern any geographically meaningful patterns. Some plants produce cleistogamous flowers only, and some plants have prominent lateral leaf veins; it is not known if these variations occur within the flora area.