Distribution
Belarus, Estonia, Finland, Germany, Hungary, Poland, Romania, Slovakia, Sweden, Ukraine

Native to eastern and Central Europe, Sweden and Poland and extends into Western Siberia. It can also be found in several regions of Russia (Central, Eastern, Northern, Northwestern and Southern European Russia and Kaliningrad) (I. Illarionova pers. comm. 2010). In Ukraine, it grows in the lowland part from the Polesian lowland to the northern part of the steppe zone, and it is rare in the eastern slopes of the Carpathian Mountains. (Bilz 2011)

Eastern Pasque Flower occurs in dry coniferous forests, Pinus sylvestris woodland south of the taiga, Picea taiga woodland, forest fringes and clearances in forests, almost bare rock pavements, including limestone pavements, steep slopes, dry grasslands and sandstone rocks (Commission of the European Communities 2009). It is known to grow on ranker soil and in dry sand steppe on acidic soil (in Hungary). In Ukraine, it is a member of the associations Querceto-Pinetum molinietosum, Peucedano-Pinetum, Festuco-Pinetum sylvestris and found in steppe communities Festuco-Brometea class. (Bilz 2011)

This is a taxonomically problematic species. Within the species P. patens several subspecies have been described; populations from Сentral Europe belong to the nominate subspecies P. patens ssp. patens (Mereďa and Hodálová 2011).

Habit: perennial herb, silky–villose throughout, with erect (or spreading) aerial shoots 5–40(–60) cm tall and 5–10 mm wide, growing from many–headed vertical caudices. Only fibrous roots present. Basal leaves: redundant in a rosette (3–)5–8(–10), erect, alternate, 3-foliolate with each leaflet dissected dichotomously. Stipules absent. Petiole present 5–10(–13) cm long with hairs longer than the diameter of the petiole. Terminal leaflet petiolulate to nearly sessile, obovate in outline, (2.5–)3–5 cm long. Leaflets spreading, straight, veins palmate. Margins dichotomously dissected throughout, apex acute to obtuse; lateral leaflets 3–4–parted (±dichotomously); ultimate segments 2–4 mm wide. Base narrowly cuneate. Surfaces villous, hairs white or translucent, simple or stellate, straight, spreading or erect; moderately dense on the abaxial surface, sparse on the adaxial surface. Inflorescences: flowering stems clearly taller than the leaves; with leaves. Solitary flowers with a villous or glabrate peduncle; involucral bracts present, 3, 1–tiered, simple, different from basal leaves, (2–)2.5–4 cm long, bases clasping, connate, margins deeply laciniate throughout; segments usually 4–6, filiform to linear, unlobed, 1–2(–3) mm wide. Surfaces villous, rarely glabrous. Flowers: large, 5.5–8.5 cm in diameter, campanulate. Epicalyx absent. Conventional sepals, 5–8, free, oblong to elliptic, coloured in blue, purple or rarely near white. Villous on the abaxial surface, glabrous on the adaxial one. Petals present. Stamens 150–200. Stamen filament glabrous. Anthers yellow; long–cylindrical; (0.8–)1.1–1.3(–1.8) mm long. Nectaries present. Ovary carpels 30–45; apocarpous. Ovaries densely hairy. One stigma per ovary, one ovule per ovary. Fruits: heads of achenes spheric to ovoid; pedicel 10–18(–22) cm long. Achenes body ellipsoid to obovoid, 3–4(–6) × ca. 1 mm long; dry, brown, not winged, villous; beak curved, 20–40 mm long, long-villous, plumose, indehiscent. One seed per achene. Styles modified and persisting in fruit; remaining straight.
Chromosome number: 2n = 16 (Tutin & Akeroyd 1993; Dutton et al. 1997; IPCN Chromosome Reports 2015)