A genus of about 7-8 species, of temperate to subarctic North America and Eurasia. There is been some controversy about the circumscription of Tofieldia relative to the related genera Pleea and Triantha (here recognized, but sometimes subsumed into Tofieldia). Some have contended that Tofieldia, Triantha, and Pleea should be treated together in a broadly circumscribed Tofieldia (Utech 1978, Zomlefer 1997c); others that all three should be treated separately (Ambrose 1980; Packer 1993; Cruden 1991). Packer in FNA (2002a) has recently recognized Triantha, Pleea, and Tofieldia as separate genera, a conclusion followed here in part because of the ancient, relictual nature of these units.
ID notes:In sterile condition, Tofieldia glabra can be distinguished from Iris verna by its minutely upwardly-scabrous margins (Iris has smooth margins).
Ref: Ambrose (1980); Azuma & Tobe (2011); Cruden (1991); Hitchcock (1944); Packer (1993); Packer (2002b) In Flora of North America Editorial Committee (2002a); Tamura In Kubitzki (1998a); Utech (1978); Zomlefer (1997c). Show full citations.