As with many members of the Euphorbia genus, what are called the flowers are really modified leaves called bracts. The bracts are very yellow. When at their peak of color, not many other plants are blooming in the zone #5 garden.
green, yellow to orange in the fall
stems will extrude a white sticky sap if cracked
up to 2-3 by 2-3 feet, clump forming
seeds that need cold stratification, careful division in the spring
Europe, escaped in the USA
Notes & Reference
#144-Missouri Botanical Gardens web site (www.missouribotanicalgarden.org), #229-Euphorbias A gardeners Guide (Rodger Turner)