barrenwort 'Brimstone Butterfly'

'Brimstone Butterfly' is a clump-forming, rhizomatous perennial 45-60cm high, with pinnate leaves, evergreen in mild winters, semi-evergreen in cold winters, formed of three long, narrowly ovate, spiny-edged and sharply tipped leaflets, which emerge tinged with pink and mature to mid-green, and branched spikes up to 45cm long of spidery flowers, of pale yellow sepals and long-spurred, greenish yellow petals, from early spring to early summer; Epimedium leaves may be used for their nests by leaf-cutting bees