Smooth oxeye (Heliopsis helianthoides), false sunflower, or oxeye sunflower, has many 2 to 3 inch golden yellow flowers that are beautiful when used in floral arrangements. Native false sunflower plants grow 2 to 6 feet tall in light shade to full sun and do best in average, well-drained, moist garden soil. This hardy perennial tolerates drought but increases more rapidly in fertile soil. Oxeye sunflowers attract nectar-seeking butterflies and other pollinators, and songbirds enjoy the ripe seeds. This is an exceptionally long-blooming flower midsummer to early autumn.