Stiff goldenrod is sometimes under the name Oligoneuron rigidum. It is a tall, 3-5 feet) semi-rhizomatous perennial with large grey-green leaves and flat clusters of yellow flowers from August to September. This large goldenrod is somewhat well behaved and is a great attractor of butterflies. Preference is for full sun to part shade and average to dry soil. Give it room as it gets large and can spread. Zone 3-9. Unknown ecotype. // Seed packet, about 50 seeds. Germination requirements: 60 days cold, moist stratification.