Russia Flora: Plant 40-60(80) cm tall. Rootstock short, ascending or vertical. Stem erect, simple or weakly branched. Basal leaves 1-5 with petioles 5-15 cm long; blade 4-8(12) cm long and wide, rounded-pentagonal, 3-5-dissected with unequally serrate-dentate lobes. Stem leaves 1-4, sessile or lower ones with petioles up to 5 cm long. Flower stalks 0.5-8 cm long, elongating in fruit up to 10(25) cm. Flowers solitary or in pairs (3), up to 3 cm in diameter. Sepals 5-7(up to 11), up to 1.5 cm long, about 1 cm wide, broadly elliptical, orange-yellow or yellow. Nectariferous petals up to 3-7(10) mm long, oblong-elliptical, reddish-orange. Nectary pit at height of about 1.5 mm. Anthers about 2 mm long, oblong-elliptical. Carpels 5-15, up to 10 mm long. Style up to 3 mm long, mostly curved. 2n = 16 (Sokolovskaya, 1963).

Distribution: Aldan, Kamchatka, Commander Islands, Northern Kuriles, Upper Zeya, Bureya, Amgun, Ussuri (north, central), Southern Kuriles (Figure 4). - In upland and floodplain meadows, forest edges, clearings; on plains and hills, on sodded and rocky-gravelly slopes, cliffs, up to the alpine zone. Flowering period: June-August. - General distribution: Eastern Siberia; North America (Aleutian Islands). - Described from Kamchatka: "Kamtschatka - Rieder. Cult. in horti Petropol. 1837. Fisch. et Mey." (type - LE).

Note: T. riederianus Fisch. et Mey. subsp. uncinatus (Sipl.) A. Luferov is distinguished by linear-spatulate petals, usually 1-3 mm shorter than stamens (Aldan, Upper Zeya, Bureya, Amgun; Eastern Siberia: Transbaikalia, Yakutia).