The name ‘Evening’ applies to O. biennis and not to the perennial kinds mentioned below, though all have the same tendency to open their at eventide. O. missouriensis, makes a wide summer surface spread, dense with glaucous and from July to September, nestle large canary yellow cups of great beauty. The is fangy and not very large considering the amount of growth and it is a better subject for a sunny bank than amongst other more upright perennials. O. ‘Fireworks’ makes a more compact plant with colourful leaves in spring and twiggy to 1 y2 feet carrying bright yellow flowers from June to August. O. cinaeus, is very similar though vernal foliage is even more colourful. There are several other yellows, of similar neat clumpy habit, all very showy, with flowers 2 inches or more across, during the same period. ‘ Yellow River’ grows to about 18 inches, but O. ‘Highlight’ is 2 feet, flowering with great profusion but sometimes needing supports.
O. missouriensis can only be increased by, but for the rest, spring division is best and any good garden soil suits them.’