Thistle poppy has stem leaves and basal leaves. The basal leaves are wide oblanceolate, oval or obovate, about 5-20cm long and 2.5-7.5cm wide. The apex is sharp, the base is wedge-shaped, the edge is pinnate, the lobes have wavy teeth, and the teeth have sharp spines. Cauline and basal form the same, the upper part smaller.
The leaves of Papaver nudicaule are all basal, ovate to lanceolate in outline, about 3-8 cm long, apex acute or round, base expanded into sheath, margin pinnately or completely split, lobes entire.
Thistle poppy usually grows on the top of the short branch alone, but also has a few cymes, 6 petals, which are wide obovate, yellow or orange.
The scape of Papaver nudicaule is cylindrical. The flowers are solitary on the scape. There are 4 petals, which are broadly cuneiform or obovate. The color is similar to the former. They are yellow, light yellow or orange, and also red.
