Herbs, perennial, not succulent, glabrous or glandular; resin canals rarely obvious. Rhizomes slender or tuberous; roots fibrous. Stems erect, usually simple. Leaves in terminal whorl or cluster, dimorphic, with smaller cauline and alternate ones proximally (some ± scalelike); petiole present (distal) or absent (proximal); blade lanceolate or oblanceolate to elliptic, suborbiculate, obovate, or spatulate, base cuneate, margins entire, plane, apex acuminate, acute, or obtuse to rounded, surfaces glabrous. Inflorescences axillary in distal leaves, solitary flowers. Pedicels present. Flowers: sepals (5-)7(-9), green, calyx lobes lanceolate or lanceolate-linear, much longer than tube; petals (5-)7(-9), corolla white to pink, rose, or pinkish lavender, rotate, lobes longer than tube, apex acute or acuminate; stamens (5-)7(-9); filaments connate basally. Fruits capsular, globose, dehiscence valvate. Seeds 2-15, black or reddish brown, globose, with deciduous, white, netlike covering. x = 35, 42. The number of species recognized in treatments of Trientalis has varied from two to four; in some, only T. europaea and T. borealis have been recognized, sometimes T. latifolia has also been recognized, while other authors have segregated the northern Pacific populations of T. europaea as T. arctica. We consider only three to be solid species.
Fls ordinarily 7-merous; cal deeply divided into nearly separate lance-linear sep; cor rotate, with very short tube and lanceolate to ovate lobes; stamens at the base of the cor, the slender filaments connected by a membranous ring; capsule 5-valved, many-seeded; low herbs, perennial by a slender rhizome, bearing a few lvs all or mostly clustered in a whorl at the top, from the axils of which appear one or more white fls on long, slender pedicels. 3, N. Temp.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.