Diapensia

Linnaeus
Sp. Pl. 1: 141. 1753.
,
Gen. Pl. ed. 5, 69. 1754 ,.
Common names: Pincushion plant
Etymology: Greek dia-, composed, and pente, five, alluding to sepal, petal, and stamen numbers
Treatment appears in FNA Volume 8. Treatment on page 337. Mentioned on page 332, 333.

Subshrubs, forming tussocks, cushions, domes, or mats, caulescent, taprooted. Stems mostly prostrate to decumbent, branched; branches procumbent or decumbent to erect. Leaves cauline, mostly opposite or compactly whorled, densely imbricate or crowded, 3–15 mm; petiole present or absent; blade oblong-lanceolate to narrowly spatulate, obovate, or spatulate-elliptic, slightly falcate, margins entire, apex acute or obtuse, surfaces glabrous, appearing 1-veined, sometimes with 1–2, indistinct, lateral veins. Inflorescences solitary flowers, pedicellate to subsessile, immediately subtended by 2–3 bracts. Pedicels ebracteate, elongating after anthesis. Flowers: sepals distinct or connate proximally; petals connate in proximal 1/2, corolla cupulate to campanulate, 7–10 mm, lobes white to cream or pinkish tinged to rose, margins entire; anthers 2-locular, without basal spurs, longitudinally dehiscent; filaments adnate to corolla tube; staminodes absent or vestigial. x = 6.

Distribution

North America, n Europe, Asia.

Discussion

Species 5 (2 in the flora).

The three temperate species of Diapensia are endemic to the Sino-Himalayan Mountains. They differ as a group from the two boreal species by their production of vestigial staminodes (see F. Ludlow 1976).

Key

1 Plants forming tussocks; branches not adventitiously rooted; leaf blades oblong-oblanceolate to narrowly spatulate, 7-15 × 1.3-2.3 mm, margins with narrow hyaline flange proximally. Diapensia lapponica
1 Plants usually forming mats or low mounds or cushions; branches adventitiously rooted; leaf blades obovate to spatulate-elliptic, 3-8(-12) × 1.5-2.2(-3) mm, margins sometimes with narrow hyaline flange. Diapensia obovata