Fritillaria thunbergii var verticilliata or F. thunbergii Syn F. verticilliata

From S. Siberia to Japan. Tall easy woodland species for me, has tendrils to clamber up other vegetation, in its homeland this is often grass. It can tolerate dry conditions once established and poor soils. Nice and moist in spring is best. Green speckled blooms in late August. 40-50cm high in part shade. 

Tendril photograph by James Steakley Wikimedia