Ballhead Sandwort

Eremogone congesta is highly polymorphic; it has been been divided into 11 varieties (nine recognized here), most of which are distinctive and locally distributed. M. F. Baad (1969) noted two patterns of variation of different origin within E. congesta, but he did not present a revised classification.

While most specimens of the four varieties with dense inflorescences do not exhibit evident pedicels, the occasional plant does bear one or more pedicels to 1-2 mm, sometimes in secondary inflorescences.

Plants tufted or sometimes mat-ted, green, not glaucous, with woody base. Stems ± erect, 3-40(-50) cm, glabrous or often stipitate-glandular. Leaves: basal leaves persistent or not; cauline leaves in 3-5 pairs, similar, but reduced distally; basal blades erect-ascending to arcuate-spreading, subulate or needlelike to filiform, (0.8-)2-11(-14) cm × 0.4-2 mm, flexuous or rigid, herbaceous to ± fleshy, apex obtuse to sharply acute or spinose, glabrous, sometimes glaucous. Inflorescences 3-50+-flowered, congested and capitate or sometimes open, umbellate cymes. Pedicels 0.1-7(-15) mm or ± absent, usually glabrous, rarely stipitate-glandular. Flowers: sepals 1-3-veined, sometimes obscurely so, ovate to lanceolate, 3-6.5 mm, not expanding in fruit, margins narrow, apex obtuse or acute to acuminate, rarely spinose, glabrous (or glandular in var. prolifera); petals white, oblong, 5-8(-10) mm, 1.5-2 times as long as sepals, apex entire to slightly emarginate; nectaries as lateral and abaxial mound with crescent-shaped groove at base of filaments opposite sepals, 0.3 × 0.15-0.2 mm. Capsules 3.5-6 mm, glabrous. Seeds reddish brown to black, broadly ellipsoid to ovoid, 1.4-3 mm, tuberculate; tubercles low, rounded, often elongate.

Arenaria congesta Nuttall in J. Torrey and A. Gray, Fl. N. Amer. 1: 178. 1838

Eremogone congesta is a species of flowering plant in the family Caryophyllaceae known by the common name ballhead sandwort. It is native to western North America from central Canada to the American southwest.