Heliopsis helianthoides - The showy, long-lasting yellow flowers of Ox-eye Sunflower are very easy to grow, and generally reach heights of up to 1.5 metres (3-5 feet). This native plant likes full sun and average soil conditions, but is also adaptable and will tolerate poor, dry soils. Ox-eye sunflower will often spread if not kept in check. In nature, it is found along stream banks and meadows, and ranges from Canada south into the United States.